small update

Don't throw away the right hand time of changes

.gitignore

@@ -1,2 +1,40 @@
 /target
 Cargo.lock
+
+# Created by https://www.toptal.com/developers/gitignore/api/macos
+# Edit at https://www.toptal.com/developers/gitignore?templates=macos
+
+### macOS ###
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+### macOS Patch ###
+# iCloud generated files
+*.icloud
+
+# End of https://www.toptal.com/developers/gitignore/api/macos

Cargo.toml

@@ -1,12 +1,16 @@
 [package]
-name = "VCDViewer"
+name = "fastwave_backend"
 version = "0.1.0"
 edition = "2021"
 
+[profile.release]
+debug = 1
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
 num = "0.4"
-clap = { version = "3.1.8", features = ["derive"] }
+clap = { version = "4.4.6", features = ["derive"] }
 chrono = "0.4"
-function_name = "0.3.0"
+# TODO : remove itertools once date parser is reworked.
+itertools = "0.11"

LICENSE-GPLV3

@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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+  14. Revised Versions of this License.
+
+  The Free Software Foundation may publish revised and/or new versions of
+the GNU General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+  Each version is given a distinguishing version number.  If the
+Program specifies that a certain numbered version of the GNU General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
+Foundation.  If the Program does not specify a version number of the
+GNU General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.

LICENSE-YEHOWSHUA

@@ -0,0 +1,2 @@
+This codebase is also licensed to Yehowshua Immanuel to use
+in any manner Yehowshua Immanuel sees fit.

README.md

@@ -1,71 +1,131 @@
-# Disclaimer
+Copyright(2023) - Yehowshua Immanuel
-PROPRIETARY - Copyright - Yehowshua Immanuel
 
-# The Beginnings of a high-performance, low memory footprint VCD Viewer in Rust for massive multi-GB waveforms
+# Vision
+Imagine being able to visualize a CPU pipeline diagram by merely loading a simulation waveform dump, sprinkling in a bit of code, and dragging and dropping some diagram blocks into the visualizer. This project aims to offer such an experience.
 
-## Current Features
+Since this project is written in Rust, it should also be able to run in the browser via web-assembly.
- - very fast
- - loads 400MB of VCD waveform per second on an 8 core 2017 desktop CPU with NVMe storage
- - consumes roughly between 10 - 50MB of memory per GB of waveform
 
-## Planed Features
+# Status
- - elegant/pretty UI
+As of January 2024, work on the Fastwave Backend is stalled. It has been a fun journey watching Fastwave enable the first iterations of the [surfer waveform viewer](https://surfer-project.org). Now surfer uses an even better backend called [Wellen](https://github.com/ekiwi/wellen?tab=readme-ov-file). Go check it out! I hear it's really good. Perhaps I will soon archive the Fastwave Backend.
- - can be easily ported to work in browser via webassembly
- - allows high-performance custom Rust plugins to manipulate and
-   generate new waveforms live
 
-## Running
+Browser demo: https://app.surfer-project.org/
 
-Make sure you have a test vcd file to get you started. You can grab
+Screenshot of surfer frontend below:
-a large VCD file from
+<img width="1609" alt="image" src="https://github.com/ThePerfectComputer/FastWaveBackend/assets/103011002/63deffc0-98b0-405f-b093-74d10b422b01">
+
+# A High performance, VCD Parser written in Rust
+
+I hope for a GUI that eventually looks like the following...
+
+![](assets/FastWaveMockup.png)
+
+# Current Features
+
+ - Robust Error Handling
+   
+   FastWave currently offers highly robust error handling(at least on the sample 
+   VCD files in this repository) which GTKWave doesn't have. For
+   example, selecting the ``UTILIZATON_ENABLED`` signal after opening 
+   [test2x2_regex22_string1.vcd](./test-vcd-files/xilinx_isim/test2x2_regex22_string1.vcd)
+   (one of the sample xilinx vcd test files) in GtkWave, will crash GtkWave since
+   this signal is malformed. FastWave on the otherhand simply notes that the
+   signal is malformed.
+
+# Performance
+
+## Methods
+I have been testing performance on a 3.04GB VCD file that can be found 
 [here](https://drive.google.com/file/d/1pfm2qo2l8fGTHHJ8TLrg1vSGaV_TUbp2/view?usp=sharing).
 
+For getting the GtkWave results, I fired up GtkWave, clicked on 
+``File``->``Open New Window``, and selected the VCD file linked to above.
+I started my stopwatch as soon as I pressed enter to beging loading the VCD
+file, and stopped my stopwatch once the GtkWave titlebar reached 100%.
+   
+To get the memory consumption, I opened Activity Monitor on Mac, and recorded
+the GtkWave memory usage before and after loading the large VCD file, and 
+took the difference.
+
+I noticed that when running FastWave in the VsCode terminal as opposed
+to the MacOS system terminal or the Lapce terminal, FastWave is notably
+slower.
+
+## Results
+
+LZ4 should really improve memory usage once I add it. Note that GTKWave uses LZ4 on the fly.
+
+| Software | Time(s) | Memory(MB) |
+|----------|---------|------------|
+| FastWave | ~27.30  | 1100+      |
+| GtkWave  | ~30     | 89.8       |
+
+
+# Current Limitations
+Unable to handle VCD files that have signals with more than 
+2^32 - 1 = 4,294,967,295 deltas/changes.
+
+# Running
+
+This repository comes with several smaller VCD files emitted from
+various EDA tools. If you want a larger VCD file, grab one from
+[here](https://drive.google.com/file/d/1pfm2qo2l8fGTHHJ8TLrg1vSGaV_TUbp2/view?usp=sharing).
+
+Here are some examples you can run:
 The first build of the program may take some time.
 
-``cargo run --release test-vcd-files/aldec/SPI_Write.vcd``
+1. ``cargo run --release --example parse_vcd tests/vcd-files/aldec/SPI_Write.vcd``
+2. ``cargo run --release --example vcd``
+
+You can run all the tests with ``cargo test``
+
+# Testing on Bad Files
+You may wish to test the parser on a malformed VCD just to make
+sure that the parser gives useful/sane errors.
+
+Here's a command to test on a malformed VCD:
+``cargo run --release --example parse_vcd tests/vcd-files/VCD_file_with_errors.vcd``
+
 
 # TODO
- - [x] We need a way to merge lines.
- - [ ] Consider what to do with don't care values
-      will probably just convert them to strings for now.
- - [ ] Test for speed and see if stream of bytes is helpful
- - [ ] Include line and possible column numbers
- - [ ] Change states to lowercase
- - [ ] We need to start regression testing the parser over all files
- - [ ] Take a look at GTKWave parser to compare effificiency.
- - [ ] Send survey to community channel.
 
-# Probably No Longer Needed
+## Features and Other
- - [ ] Should insert nodes in BFS order
+ - [ ] add documenting comments
+ - [ ] make signal query private until later?
+ - [ ] add signal query code to example once interface is finalized
+ - [ ] change crate name to vcd_fast_parse
+ - [ ] perhaps we should be looking up signal values on the VCD class
+ - [ ] perhaps we should be returning signal trees from the VCD class
+ - [ ] add lz4 compression support and compare memory perf before and after
+       - [ ] may need to refactor with allow for get_mut for dynamic
+             compression-decompression for multiple signal structs 
+             at once to allow for multi-threading
+ - [ ] test against large waveforms from the
+       [verilog-vcd-parser](https://github.com/ben-marshall/verilog-vcd-parser)
+       tool
+ - [ ] (a bit of work) consolidate error messages in validation phase
+ - [ ] once the access patterns of the GUI frontend are well understood,
+       create specific functions and restrict as many types to private
+       as possible
+ - [ ] Print out git commit or release number.
+ - [ ] do a read through all the code - look for uneeded code
+ - [ ] Move part of the performance section to another markdown file.
 
-# Files
+## Repairs
- - ./test-vcd-files/aldec/SPI_Write.vcd
+ - [ ] replace str bracket indices with get(slice)
- - ./test-vcd-files/ghdl/alu.vcd
+ - [ ] make a custom date parser for possibly up to 18 different versions(that is, for each possible tool).
- - ./test-vcd-files/ghdl/idea.vcd
+ - [ ] Consolidate error messages and add cursors throughout.
- - ./test-vcd-files/ghdl/pcpu.vcd
+ - [ ] Add file and line to the enum errors.
- - ./test-vcd-files/gtkwave-analyzer/perm_current.vcd
+ - [ ] Fix warnings especially usage and restriction warnings once I'm
- - ./test-vcd-files/icarus/CPU.vcd
+       able to successfully parse all sample VCDs.
- - ./test-vcd-files/icarus/rv32_soc_TB.vcd
+
- - ./test-vcd-files/icarus/test1.vcd
+## Code Consistency
- - ./test-vcd-files/model-sim/CPU_Design.msim.vcd
+ - [ ] Change error messages to line and filenames. Go through all calls to unwrap.
- - ./test-vcd-files/model-sim/clkdiv2n_tb.vcd
+   - [ ] search for any unwraps or any direct vectors indexing
- - ./test-vcd-files/my-hdl/Simple_Memory.vcd
+ - [ ] Handle TODOs
- - ./test-vcd-files/my-hdl/sigmoid_tb.vcd
+ - [ ] Remove debug code/comments.
- - ./test-vcd-files/my-hdl/top.vcd
+
- - ./test-vcd-files/ncsim/ffdiv_32bit_tb.vcd
+## Documentation
- - ./test-vcd-files/quartus/mipsHardware.vcd
+ - [ ] Document indexing structure with diagram and possibly include the rational
- - ./test-vcd-files/quartus/wave_registradores.vcd
+
- - ./test-vcd-files/questa-sim/dump.vcd
+## Marketing
- - ./test-vcd-files/questa-sim/test.vcd
+ - [ ] Send survey to community 
- - ./test-vcd-files/riviera-pro/dump.vcd
- - ./test-vcd-files/systemc/waveform.vcd
- - ./test-vcd-files/treadle/GCD.vcd
- - ./test-vcd-files/vcs/Apb_slave_uvm_new.vcd
- - ./test-vcd-files/vcs/datapath_log.vcd
- - ./test-vcd-files/vcs/processor.vcd
- - ./test-vcd-files/verilator/swerv1.vcd
- - ./test-vcd-files/verilator/vlt_dump.vcd
- - ./test-vcd-files/vivado/iladata.vcd
- - ./test-vcd-files/xilinx_isim/test.vcd
- - ./test-vcd-files/xilinx_isim/test1.vcd
- - ./test-vcd-files/xilinx_isim/test2x2_regex22_string1.vcd

examples/parse_vcd.rs

@@ -0,0 +1,33 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use clap::Parser;
+use std::fs::File;
+
+use fastwave_backend::parse_vcd;
+
+#[derive(Parser)]
+struct Cli {
+    /// The path to the file to read
+    path: std::path::PathBuf,
+}
+
+fn main() -> std::io::Result<()> {
+    let args = Cli::parse();
+
+    use std::time::Instant;
+
+    let now = Instant::now();
+    let file = File::open(&args.path)?;
+    parse_vcd(file).unwrap();
+    let elapsed = now.elapsed();
+
+    println!(
+        "Parsed VCD file {} : {:.2?}",
+        &args.path.as_os_str().to_str().unwrap(),
+        elapsed
+    );
+
+    Ok(())
+}

examples/vcd.rs

@@ -0,0 +1,81 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use std::fs::File;
+
+use fastwave_backend::{parse_vcd, ScopeIdx, SignalIdx, VCD};
+
+fn indented_print(indent: u8, name: &String) {
+    for _ in 0..indent {
+        print!("  |");
+    }
+    print!("---");
+    println!("{name}");
+}
+
+// TODO: refactor into more general visitor pattern that takes a
+// function as an argument.
+fn visit_all_scopes(vcd: &VCD) {
+    fn visit_all_scope_children(root_idx: ScopeIdx, vcd: &VCD, indent: u8) {
+        if vcd.child_scopes_by_idx(root_idx).is_empty() {
+        } else {
+            for child_scope_idx in vcd.child_scopes_by_idx(root_idx) {
+                indented_print(indent, vcd.scope_name_by_idx(child_scope_idx));
+                for signal_idx in vcd.get_children_signal_idxs(child_scope_idx) {
+                    let signal = vcd.signal_from_signal_idx(signal_idx);
+                    let SignalIdx(idx) = signal_idx;
+                    indented_print(indent + 1, &format!("{},{}", signal.name(), idx));
+                }
+                visit_all_scope_children(child_scope_idx, vcd, indent + 1);
+            }
+        }
+    }
+    for root_scope_idx in vcd.root_scopes_by_idx() {
+        indented_print(0, vcd.scope_name_by_idx(root_scope_idx));
+        visit_all_scope_children(root_scope_idx, vcd, 1u8);
+    }
+}
+
+fn main() -> std::io::Result<()> {
+    use std::time::Instant;
+
+    // we start by printing out the entire signal tree of
+    // a parsed VCD
+    let now = Instant::now();
+    let file_path = "tests/vcd-files/icarus/CPU.vcd";
+    let file = File::open(file_path)?;
+    let vcd = parse_vcd(file).unwrap();
+    let elapsed = now.elapsed();
+    println!("Parsed VCD file {} : {:.2?}", file_path, elapsed);
+
+    println!("Printing Scopes");
+    visit_all_scopes(&vcd);
+    println!("Done Printing Scopes");
+    println!();
+
+    // we then parse another VCD, print its signal tree and
+    // query some values on its timeline
+    let now = Instant::now();
+    let file_path = "tests/vcd-files/amaranth/up_counter.vcd";
+    let file = File::open(file_path)?;
+    let vcd = parse_vcd(file).unwrap();
+    let elapsed = now.elapsed();
+    println!("Parsed VCD file {} : {:.2?}", file_path, elapsed);
+
+    println!("Printing Scopes");
+    visit_all_scopes(&vcd);
+    println!("Done Printing Scopes");
+
+    let state_signal = vcd.signal_from_signal_idx(SignalIdx(4));
+    let name = state_signal.name();
+
+    let timestamps = vec![31499_000u32, 31500_000u32, 57760_000u32];
+    for timestamp in timestamps {
+        let time = num::BigUint::from(timestamp);
+        let val = state_signal.query_string_val_on_tmln(&time, &vcd).unwrap();
+        println!("Signal `{name}` has value `{val}` at time `{time}`");
+    }
+
+    Ok(())
+}

src/lib.rs

@@ -0,0 +1,12 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+
+mod vcd;
+pub use vcd::parse::parse_vcd;
+pub use vcd::signal::{Signal, SignalType, SignalValue, SignalErrors};
+pub use vcd::types::{Metadata, Timescale, Version};
+pub use vcd::types::{ScopeIdx, SignalIdx, VCD};
+
+pub use num::BigUint;

src/main.rs

@@ -1,305 +0,0 @@
-use std::io::prelude::*;
-use std::io;
-use std::fs::File;
-use std::collections::BTreeMap;
-use chrono::prelude::*;
-use ::function_name::named;
-
-use num::*;
-use clap::Parser;
-
-#[derive(Parser)]
-struct Cli {
-    /// The path to the file to read
-    #[clap(parse(from_os_str))]
-    path: std::path::PathBuf}
-
-
-// TODO: implement any timescales greater than a second
-#[derive(Debug)]
-enum Timescale {ps, ns, us, ms, s, unit}
-
-#[derive(Debug)]
-struct Scope_Idx(usize);
-
-#[derive(Debug)]
-struct Signal_Idx(usize);
-
-#[derive(Debug)]
-struct Version(String);
-
-#[derive(Debug)]
-struct Metadata {
-    date      : Option<DateTime<Utc>>,
-    version   : Option<Version>,
-    timescale : (Option<u32>, Timescale)}
-
-#[derive(Debug)]
-enum SignalGeneric{
-    Signal{
-        name           : String,
-        timeline       : BTreeMap<BigInt, BigInt>,
-        scope_parent   : Scope_Idx},
-    SignalAlias{
-        name          : String,
-        signal_alias  : Signal_Idx}
-}
-
-#[derive(Debug)]
-struct Scope {
-    name          : String,
-    child_signals : Vec<Signal_Idx>,
-    child_scopes  : Vec<Scope_Idx>}
-
-
-#[derive(Debug)]
-struct VCD {
-    metadata    : Metadata,
-    all_signals : Vec<SignalGeneric>,
-    // the root scope should always be placed at index 0
-    all_scopes  : Vec<Scope>}
-
-#[derive(Debug)]
-enum Date_Parser_State {Begin, Parsing}
-#[derive(Debug)]
-enum Version_Parser_State {Begin, Parsing}
-#[derive(Debug)]
-enum Timescale_Parser_State {Begin, Parsing}
-#[derive(Debug)]
-enum Signal_Tree_Parser_State {Begin, Parsing}
-
-
-#[derive(Debug)]
-enum Parser_State {
-    Date(Date_Parser_State),
-    Version(Version_Parser_State), 
-    Timescale(Timescale_Parser_State), 
-    Signal_Tree(Signal_Tree_Parser_State),
-    Parse_Signal_Values}
-
-struct VCD_Parser<'a> {
-    vcd_parser_state   : Parser_State,
-    buffer             : Option<String>,
-
-    vcd                : &'a mut VCD,
-    curr_scope         : Option<&'a Scope>,
-    curr_parent_scope  : Option<&'a Scope>}
-
-impl VCD {
-    pub fn new() -> Self {
-        let metadata = Metadata {
-            date      : None,
-            version   : None,
-            timescale : (None, Timescale::unit)};
-        VCD {
-            metadata    : metadata,
-            all_signals : Vec::<SignalGeneric>::new(),
-            all_scopes  : Vec::<Scope>::new()}
-        }
-    }
-
-impl<'a> VCD_Parser<'a> {
-    pub fn new(vcd : &'a mut VCD) -> Self {
-        VCD_Parser {
-            vcd_parser_state : Parser_State::Date(Date_Parser_State::Begin),
-
-            buffer      : None,
-            vcd : vcd,
-            curr_scope : None,
-            curr_parent_scope : None
-        }
-    }
-
-    pub fn parse_word(&mut self, word : &str) -> Result<(), String> {
-        let mut state = &mut self.vcd_parser_state;
-        let t = &self.vcd;
-        match state {
-            Parser_State::Date(_) => self.parse_date(word),
-            Parser_State::Version(_) => self.parse_version(word),
-            Parser_State::Timescale(_) => self.parse_timescale(word),
-            // TODO : Enable the following in production
-            // _ => Err(format!("parser in bad state : {state:?}"))
-            // TODO : Disable the following in production
-            _ => {
-                Err(format!("parser in bad state : {state:?}; {t:?}"))
-            }
-        }
-    }
-
-    #[named]
-    pub fn parse_date(&mut self, word : &str) -> Result<(), String> {
-        let mut state = &mut self.vcd_parser_state;
-        match state {
-            Parser_State::Date(Date_Parser_State::Begin) =>
-                match word {
-                    "$date" => {
-                        *state = Parser_State::Date(Date_Parser_State::Parsing); 
-                        Ok(())
-                    }
-                    _ => {
-                        *state = Parser_State::Version(Version_Parser_State::Begin); 
-                        self.parse_version(word)
-                    }
-                }
-            Parser_State::Date(Date_Parser_State::Parsing) =>
-                match word {
-                    "$end" => {
-                        let s  = self.buffer.take().unwrap();
-                        let dt = Utc.datetime_from_str(s.as_str(), "%a %b %e %T %Y")
-                        .expect(&format!("invalid date {s}").as_str());
-                        *state = Parser_State::Version(Version_Parser_State::Begin); 
-                        self.vcd.metadata.date = Some(dt);
-                        Ok(())
-                    }
-                    _ => {
-                        if let Some(ref mut buffer) = self.buffer {
-                            buffer.push_str(" ");
-                            buffer.push_str(word);
-                        }
-                        else {
-                            self.buffer = Some(word.to_string());
-                        }
-                        Ok(())
-                    }
-                }
-            _   => Err(format!("{state:?} should be unreachable within {}.",function_name!())),
-
-        }
-    }
-
-    #[named]
-    pub fn parse_version(&mut self, word : &str) -> Result<(), String> {
-        let mut state = &mut self.vcd_parser_state;
-        match state {
-            Parser_State::Version(Version_Parser_State::Begin) =>
-                match word {
-                    "$version" => {
-                        *state = Parser_State::Version(Version_Parser_State::Parsing); 
-                        Ok(())
-                    }
-                    _ => {
-                        *state = Parser_State::Timescale(Timescale_Parser_State::Begin); 
-                        Ok(())
-                    }
-                }
-            Parser_State::Version(Version_Parser_State::Parsing) =>
-                match word {
-                    "$end" => {
-                        let s = self.buffer.take().unwrap();
-                        self.vcd.metadata.version = Some(Version(s));
-                        *state = Parser_State::Timescale(Timescale_Parser_State::Begin); 
-                        Ok(())
-                    }
-                    _ => {
-                        if let Some(ref mut buffer) = self.buffer {
-                            buffer.push_str(" ");
-                            buffer.push_str(word);
-                        }
-                        else {
-                            self.buffer = Some(word.to_string());
-                        }
-                        Ok(())
-                    }
-                }
-            _   => Err(format!("{state:?} should be unreachable within {}.",function_name!())),
-
-        }
-    }
-
-    #[named]
-    pub fn parse_timescale(&mut self, word : &str) -> Result<(), String> {
-        let mut state = &mut self.vcd_parser_state;
-        match state {
-            Parser_State::Timescale(Timescale_Parser_State::Begin) =>
-                match word {
-                    "$timescale" => {
-                        *state = Parser_State::Timescale(Timescale_Parser_State::Parsing); 
-                        Ok(())
-                    }
-                    _ => {
-                        *state = Parser_State::Signal_Tree(Signal_Tree_Parser_State::Begin); 
-                        Ok(())
-                    }
-                }
-            Parser_State::Timescale(Timescale_Parser_State::Parsing) =>
-                match word {
-                    "$end" => {
-                        let s = self.buffer.take().unwrap();
-                        let s = s.split_ascii_whitespace();
-                        let s = s.collect::<Vec<&str>>();
-
-                        let scalar = s[0].to_string().parse::<u32>().unwrap();
-                        let unit = s[1];
-                        let unit = match unit {
-                            "ps" => Ok(Timescale::ps),
-                            "ns" => Ok(Timescale::ns),
-                            "us" => Ok(Timescale::us),
-                            "ms" => Ok(Timescale::ms),
-                            "s"  => Ok(Timescale::s),
-                            // TODO : see if there is a way to easily print out all enum variants
-                            // _    => Err(format!("{word} is not a valid unit of time in {Timescale}"))
-                            _    => Err(format!("{unit} is not a valid unit"))
-                        }.unwrap();
-
-                        dbg!(s);
-                        self.vcd.metadata.timescale = (Some(scalar), unit);
-                        *state = Parser_State::Timescale(Timescale_Parser_State::Begin); 
-                        Ok(())
-                    }
-                    _ => {
-                        if let Some(ref mut buffer) = self.buffer {
-                            buffer.push_str(" ");
-                            buffer.push_str(word);
-                        }
-                        else {
-                            self.buffer = Some(word.to_string());
-                        }
-                        Ok(())
-                    }
-                }
-            _   => Err(format!("{state:?} should be unreachable within {}.",function_name!())),
-
-        }
-    }
-}
-
-fn yield_word_and_apply(file : File, mut f : impl FnMut(&str) -> Result<(), String>) {
-    let mut reader = io::BufReader::new(file);
-
-    let mut buffer = String::new();
-    let mut EOF = false;
-    let line_chunk_size = 25;
-
-    while {!EOF} {
-        for _ in 0..line_chunk_size {
-            let bytes_read = reader.read_line(&mut buffer).unwrap();
-            if bytes_read == 0 {
-                EOF = true;
-                break
-            }
-        }
-
-        let words = buffer.split_ascii_whitespace();
-
-        for word in words {
-            f(word).unwrap();
-        }
-        
-        buffer.clear();
-    }
-
-}
-
-fn main() -> std::io::Result<()> {
-    let args = Cli::parse();
-
-    let file           = File::open(&args.path)?;
-
-    let mut vcd = VCD::new();
-    let mut parser = VCD_Parser::new(&mut vcd);
-
-    yield_word_and_apply(file, |word| {parser.parse_word(word)});
-    dbg!(&vcd);
-
-    Ok(())
-}

src/vcd.rs

@@ -0,0 +1,10 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+
+pub(crate) mod parse;
+mod reader;
+pub(crate) mod signal;
+pub(crate) mod types;
+mod utilities;

src/vcd/parse.rs

@@ -0,0 +1,35 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+
+mod combinator_atoms;
+mod events;
+mod metadata;
+mod scopes;
+mod types;
+
+pub fn parse_vcd(file: impl std::io::Read) -> Result<super::types::VCD, String> {
+    let mut word_gen = super::reader::WordReader::new(file);
+
+    let header = metadata::parse_metadata(&mut word_gen)?;
+
+    // later, we'll need to map parsed ascii symbols to their
+    // respective signal indexes
+    let mut signal_map = std::collections::HashMap::new();
+
+    // after we parse metadata, we form the VCD object
+    let mut vcd = super::types::VCD {
+        metadata: header,
+        tmstmps_encoded_as_u8s: vec![],
+        all_signals: vec![],
+        all_scopes: vec![],
+        root_scopes: vec![],
+        largest_timestamp: None,
+    };
+
+    scopes::parse_scopes(&mut word_gen, &mut vcd, &mut signal_map)?;
+    events::parse_events(&mut word_gen, &mut vcd, &mut signal_map)?;
+
+    Ok(vcd)
+}

src/vcd/parse/combinator_atoms.rs

@@ -0,0 +1,83 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use super::super::reader::{next_word, WordReader};
+use super::types::ParseResult;
+
+pub(super) fn digit(chr: u8) -> bool {
+    let zero = b'0';
+    let nine = b'9';
+
+    (chr >= zero) && (nine >= chr)
+}
+
+pub(super) fn take_until(word: &str, pattern: u8) -> ParseResult<'_> {
+    let mut new_start = 0;
+
+    for chr in word.as_bytes() {
+        if *chr == pattern {
+            break;
+        } else {
+            new_start += 1;
+        }
+    }
+
+    ParseResult {
+        matched: &word[0..new_start],
+        residual: &word[new_start..],
+    }
+}
+
+pub(super) fn take_while(word: &str, cond: fn(u8) -> bool) -> ParseResult<'_> {
+    let mut new_start = 0;
+
+    for chr in word.as_bytes() {
+        if cond(*chr) {
+            new_start += 1;
+        } else {
+            break;
+        }
+    }
+
+    ParseResult {
+        matched: &word[0..new_start],
+        residual: &word[new_start..],
+    }
+}
+
+pub(super) fn tag<'a>(word: &'a str, pattern: &'a str) -> ParseResult<'a> {
+    let lhs = word.as_bytes().iter();
+    let rhs = pattern.as_bytes();
+    let iter = lhs.zip(rhs);
+    let mut new_start = 0;
+
+    let mut res = true;
+    for (c_lhs, c_rhs) in iter {
+        res = res && (c_lhs == c_rhs);
+        if !res {
+            break;
+        }
+        new_start += 1;
+    }
+
+    ParseResult {
+        matched: &word[0..new_start],
+        residual: &word[new_start..],
+    }
+}
+
+pub(super) fn ident<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+    keyword: &str,
+) -> Result<(), String> {
+    // let keyword = "module";
+    let (word, cursor) = next_word!(word_reader)?;
+
+    if word == keyword {
+        Ok(())
+    } else {
+        let err = format!("found keyword `{word}` but expected `{keyword}` on {cursor:?}");
+        Err(err)
+    }
+}

src/vcd/parse/events.rs

@@ -0,0 +1,546 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+
+use num::BigUint;
+use std::collections::HashMap;
+
+use super::super::reader::{next_word, Cursor, Line, Word, WordReader};
+use super::super::signal::{LsbIdxOfTmstmpValOnTmln, SignalEnum};
+use super::super::types::{SignalIdx, VCD};
+use super::super::utilities::{binary_str_to_vec_u8, BinaryParserErrTypes};
+
+pub(super) fn parse_events<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+    vcd: &mut VCD,
+    signal_map: &mut HashMap<String, SignalIdx>,
+) -> Result<(), String> {
+    let mut curr_tmstmp_lsb_idx = 0u32;
+    let mut curr_tmstmp_len_u8 = 0u8;
+    loop {
+        let next_word = word_reader.next_word();
+
+        // The following is the only case where eof is not an error.
+        // If we've reached the end of the file, then there is obviously
+        // nothing left to do...
+        if next_word.is_none() {
+            break;
+        };
+
+        let (word, cursor) = next_word.unwrap();
+        let Cursor(Line(_), Word(word_in_line_idx)) = cursor;
+        // we only want to match on the first word in a line
+        if word_in_line_idx != 1 {
+            continue;
+        }
+        match &word[0..1] {
+            "$" => {}
+            "#" => {
+                let value = &word[1..];
+                let (f, l) = (file!(), line!());
+                let value_biguint = BigUint::parse_bytes(value.as_bytes(), 10)
+                    .ok_or(())
+                    .map_err(|_| {
+                        format!(
+                            "Error near {f}:{l}. Failed to parse {value} as BigInt at {cursor:?}"
+                        )
+                    })?;
+                let mut value = value_biguint.to_bytes_le();
+                // TODO : u32 helps with less memory, but should ideally likely be
+                // configurable.
+                curr_tmstmp_len_u8 = u8::try_from(value.len()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}. Failed to convert from usize to u8.",
+                        file!(),
+                        line!()
+                    )
+                })?;
+                curr_tmstmp_lsb_idx =
+                    u32::try_from(vcd.tmstmps_encoded_as_u8s.len()).map_err(|_| {
+                        format!(
+                            "Error near {}:{}. Failed to convert from usize to u32.",
+                            file!(),
+                            line!()
+                        )
+                    })?;
+                vcd.tmstmps_encoded_as_u8s.append(&mut value);
+                vcd.largest_timestamp = Some(value_biguint);
+            }
+
+            // handle the case of an n bit signal whose value must be parsed
+            "b" => {
+                let binary_value = &word[1..];
+                let observed_num_bits = u32::try_from(binary_value.len()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}, {cursor:?}. \
+                        Found signal with more than 2^32 - 1 bits.",
+                        file!(),
+                        line!()
+                    )
+                })?;
+
+                let mut value_u8: Vec<u8> = Vec::new();
+                let mut value_string = String::new();
+
+                let mut store_as_string = false;
+
+                // If we encounter other values than 0 or 1, we can recover from
+                // the error and store the value as a string.
+                // Or else, we propagate up other errors.
+                match binary_str_to_vec_u8(binary_value) {
+                    Ok(result) => {
+                        value_u8 = result;
+                    }
+                    Err(
+                        BinaryParserErrTypes::XValue
+                        | BinaryParserErrTypes::ZValue
+                        | BinaryParserErrTypes::UValue
+                        | BinaryParserErrTypes::WValue
+                        | BinaryParserErrTypes::HValue
+                        | BinaryParserErrTypes::DashValue
+                        | BinaryParserErrTypes::LValue,
+                    ) => {
+                        store_as_string = true;
+                        // Turn to lower case for consistency
+                        value_string = binary_value.to_ascii_lowercase();
+                    }
+                    Err(e) => {
+                        let (f, l) = (file!(), line!());
+                        Err(e).map_err(|e| {
+                            format!("Error near {f}:{l}. Error {e:?} at {cursor:?}.")
+                        })?;
+                    }
+                }
+
+                // this word should be the signal alias
+                let (word, cursor) = next_word!(word_reader)?;
+
+                // lookup signal idx
+                let signal_idx = signal_map.get(word).ok_or(()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}. Failed to lookup signal {word} at {cursor:?}",
+                        file!(),
+                        line!()
+                    )
+                })?;
+
+                let signal = vcd.dealiasing_signal_idx_to_signal_lookup_mut(signal_idx)?;
+
+                match signal {
+                    SignalEnum::Data {
+                        name,
+                        signal_type,
+                        ref mut signal_error,
+                        num_bits,
+                        num_bytes,
+                        nums_encoded_as_fixed_width_le_u8,
+                        string_vals,
+                        lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                        byte_len_of_num_tmstmp_vals_on_tmln,
+                        lsb_indxs_of_string_tmstmp_vals_on_tmln,
+                        byte_len_of_string_tmstmp_vals_on_tmln,
+                        ..
+                    } => {
+                        // we've already identified in a prior loop iteration that the signal has
+                        // an error
+                        if signal_error.is_some() {
+                            continue;
+                        }
+
+                        // Get the observed number of bits for the value parsed earlier
+                        // and verify that it is not greater than the numbits declared
+                        // when the signal was declared.
+                        // Also account for the error case of a bitwidth of `None`
+                        match num_bits {
+                            Some(ref num_bits) => {
+                                if observed_num_bits > *num_bits {
+                                    let (f, l) = (file!(), line!());
+                                    let msg = format!("\
+                                        Error near {f}:{l}. The bitwidth for signal {name} \
+                                        of signal_type {signal_type:?} is expected to be `{num_bits}` not \
+                                        `{observed_num_bits}`. \
+                                        This error occurred while parsing the vcd file at \
+                                        {cursor:?}");
+                                    *signal_error = Some(msg);
+                                    continue;
+                                }
+                            }
+                            None => {
+                                let (f, l) = (file!(), line!());
+                                let msg = format!(
+                                    "\
+                                    Error near {f}:{l}. The bitwidth for signal {name} \
+                                    must be specified for a signal of type {signal_type:?}. \
+                                    This error occurred while parsing the vcd file at \
+                                    {cursor:?}"
+                                );
+                                Err(msg)?;
+                            }
+                        };
+
+                        if store_as_string {
+                            lsb_indxs_of_string_tmstmp_vals_on_tmln
+                                .push(LsbIdxOfTmstmpValOnTmln(curr_tmstmp_lsb_idx));
+                            byte_len_of_string_tmstmp_vals_on_tmln.push(curr_tmstmp_len_u8);
+                            string_vals.push(value_string);
+                            Ok(())
+                        } else {
+                            // timestamp stuff
+                            lsb_indxs_of_num_tmstmp_vals_on_tmln
+                                .push(LsbIdxOfTmstmpValOnTmln(curr_tmstmp_lsb_idx));
+                            byte_len_of_num_tmstmp_vals_on_tmln.push(curr_tmstmp_len_u8);
+
+                            // value stuff
+                            // we may need to zero extend values
+                            // so that we end up storing all values
+                            // of a particular signal in a consistent
+                            // amount of bytes
+                            let bytes_required = num_bytes.ok_or_else(|| {
+                                format!("Error near {}:{}. num_bytes empty.", file!(), line!())
+                            })?;
+                            let mut curr_num_bytes =
+                                u16::try_from(value_u8.len()).map_err(|_| {
+                                    format!(
+                                        "Error near {}:{}. \
+                                     Found signal {name} with with value change of greater \
+                                     than 2^32 - 1 bits on {cursor:?}.",
+                                        file!(),
+                                        line!()
+                                    )
+                                })?;
+
+                            nums_encoded_as_fixed_width_le_u8.append(&mut value_u8);
+                            while curr_num_bytes < bytes_required {
+                                nums_encoded_as_fixed_width_le_u8.push(0u8);
+                                curr_num_bytes += 1;
+                            }
+                            Ok(())
+                        }
+                    }
+                    SignalEnum::Alias { .. } => {
+                        let (f, l) = (file!(), line!());
+                        let msg = format!(
+                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
+                                This error occurred while parsing vcd file at {cursor:?}");
+                        Err(msg)
+                    }
+                }?;
+            }
+
+            // handle the case of a one bit signal whose value is set to `0`
+            "0" => {
+                // lookup signal idx
+                let hash = &word[1..];
+                let signal_idx = signal_map.get(hash).ok_or(()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
+                        file!(),
+                        line!()
+                    )
+                })?;
+
+                let signal = vcd.dealiasing_signal_idx_to_signal_lookup_mut(signal_idx)?;
+
+                match signal {
+                    SignalEnum::Data {
+                        name,
+                        signal_type,
+                        ref mut signal_error,
+                        num_bits,
+                        num_bytes,
+                        nums_encoded_as_fixed_width_le_u8,
+                        lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                        byte_len_of_num_tmstmp_vals_on_tmln,
+                        ..
+                    } => {
+                        // if this is a bad signal, go ahead and skip it
+                        if signal_error.is_some() {
+                            continue;
+                        }
+
+                        // Get bitwidth and verify that it is 1.
+                        // Also account for the error case of a bitwidth of `None`
+                        match num_bits {
+                            Some(ref num_bits) => {
+                                if *num_bits != 1 {
+                                    let (f, l) = (file!(), line!());
+                                    let msg = format!(
+                                        "\
+                                        Error near {f}:{l}. The bitwidth for signal {name} \
+                                        of signal_type {signal_type:?} is expected to be `1` not \
+                                        `{num_bits}`. \
+                                        This error occurred while parsing the vcd file at \
+                                        {cursor:?}"
+                                    );
+                                    *signal_error = Some(msg);
+                                    continue;
+                                }
+                            }
+                            None => {
+                                let (f, l) = (file!(), line!());
+                                let msg = format!(
+                                    "\
+                                    Error near {f}:{l}. The bitwidth for signal {name} \
+                                    must be specified for a signal of type {signal_type:?}. \
+                                    This error occurred while parsing the vcd file at \
+                                    {cursor:?}"
+                                );
+                                Err(msg)?;
+                            }
+                        };
+                        // timestamp stuff
+                        lsb_indxs_of_num_tmstmp_vals_on_tmln
+                            .push(LsbIdxOfTmstmpValOnTmln(curr_tmstmp_lsb_idx));
+                        byte_len_of_num_tmstmp_vals_on_tmln.push(curr_tmstmp_len_u8);
+
+                        // value stuff
+                        // we may need to zero extend values
+                        // so that we end up storing all values
+                        // of a particular signal in a consistent
+                        // amount of bytes
+                        let bytes_required = num_bytes.ok_or_else(|| {
+                            format!("Error near {}:{}. num_bytes empty.", file!(), line!())
+                        })?;
+                        nums_encoded_as_fixed_width_le_u8.push(0u8);
+                        let mut curr_num_bytes = 1;
+                        while curr_num_bytes < bytes_required {
+                            nums_encoded_as_fixed_width_le_u8.push(0u8);
+                            curr_num_bytes += 1;
+                        }
+                        Ok(())
+                    }
+                    SignalEnum::Alias { .. } => {
+                        let (f, l) = (file!(), line!());
+                        let msg = format!(
+                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
+                             This error occurred while parsing vcd file at {cursor:?}");
+                        Err(msg)
+                    }
+                }?;
+            }
+
+            "1" => {
+                // lokup signal idx
+                let hash = &word[1..];
+                let signal_idx = signal_map.get(hash).ok_or(()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
+                        file!(),
+                        line!()
+                    )
+                })?;
+
+                let signal = vcd.dealiasing_signal_idx_to_signal_lookup_mut(signal_idx)?;
+
+                match signal {
+                    SignalEnum::Data {
+                        name,
+                        signal_type,
+                        ref mut signal_error,
+                        num_bits,
+                        num_bytes,
+                        nums_encoded_as_fixed_width_le_u8,
+                        lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                        byte_len_of_num_tmstmp_vals_on_tmln,
+                        ..
+                    } => {
+                        // if this is a bad signal, go ahead and skip it
+                        if signal_error.is_some() {
+                            continue;
+                        }
+
+                        // Get bitwidth and verify that it is 1.
+                        // Also account for the error case of a bitwidth of `None`
+                        match num_bits {
+                            Some(ref num_bits) => {
+                                if *num_bits != 1 {
+                                    let (f, l) = (file!(), line!());
+                                    let msg = format!(
+                                        "\
+                                        Error near {f}:{l}. The bitwidth for signal {name} \
+                                        of signal_type {signal_type:?} is expected to be `1` not \
+                                        `{num_bits}`. \
+                                        This error occurred while parsing the vcd file at \
+                                        {cursor:?}"
+                                    );
+                                    *signal_error = Some(msg);
+                                    continue;
+                                }
+                            }
+                            None => {
+                                let (f, l) = (file!(), line!());
+                                let msg = format!(
+                                    "\
+                                    Error near {f}:{l}. The bitwidth for signal {name} \
+                                    must be specified for a signal of type {signal_type:?}. \
+                                    This error occurred while parsing the vcd file at \
+                                    {cursor:?}"
+                                );
+                                Err(msg)?;
+                            }
+                        };
+                        // timestamp stuff
+                        lsb_indxs_of_num_tmstmp_vals_on_tmln
+                            .push(LsbIdxOfTmstmpValOnTmln(curr_tmstmp_lsb_idx));
+                        byte_len_of_num_tmstmp_vals_on_tmln.push(curr_tmstmp_len_u8);
+
+                        // value stuff
+                        // we may need to zero extend values
+                        // so that we end up storing all values
+                        // of a particular signal in a consistent
+                        // amount of bytes
+                        let bytes_required = num_bytes.ok_or_else(|| {
+                            format!("Error near {}:{}. num_bytes empty.", file!(), line!())
+                        })?;
+                        nums_encoded_as_fixed_width_le_u8.push(1u8);
+                        let mut curr_num_bytes = 1;
+                        while curr_num_bytes < bytes_required {
+                            nums_encoded_as_fixed_width_le_u8.push(0u8);
+                            curr_num_bytes += 1;
+                        }
+                        Ok(())
+                    }
+                    SignalEnum::Alias { .. } => {
+                        let (f, l) = (file!(), line!());
+                        let msg = format!(
+                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
+                             This error occurred while parsing vcd file at {cursor:?}");
+                        Err(msg)
+                    }
+                }?;
+            }
+
+            // other one bit cases
+            "x" | "X" | "z" | "Z" | "u" | "U" | "h" | "H" | "l" | "L" | "w" | "W" | "-" => {
+                // Select value and turn to lowercase for consistency
+                let val = word[0..1].to_ascii_lowercase();
+                // lokup signal idx
+                let hash = &word[1..];
+                let signal_idx = signal_map.get(hash).ok_or(()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
+                        file!(),
+                        line!()
+                    )
+                })?;
+
+                let signal = vcd.dealiasing_signal_idx_to_signal_lookup_mut(signal_idx)?;
+
+                match signal {
+                    SignalEnum::Data {
+                        name,
+                        signal_type,
+                        ref mut signal_error,
+                        num_bits,
+                        string_vals,
+                        byte_len_of_string_tmstmp_vals_on_tmln,
+                        lsb_indxs_of_string_tmstmp_vals_on_tmln,
+                        ..
+                    } => {
+                        // if this is a bad signal, go ahead and skip it
+                        if signal_error.is_some() {
+                            continue;
+                        }
+
+                        // Get bitwidth and verify that it is 1.
+                        // Also account for the error case of a bitwidth of `None`
+                        match num_bits {
+                            Some(ref num_bits) => {
+                                if *num_bits != 1 {
+                                    let (f, l) = (file!(), line!());
+                                    let msg = format!(
+                                        "\
+                                        Error near {f}:{l}. The bitwidth for signal {name} \
+                                        of signal_type {signal_type:?} is expected to be `1` not \
+                                        `{num_bits}`. \
+                                        This error occurred while parsing the vcd file at \
+                                        {cursor:?}"
+                                    );
+                                    *signal_error = Some(msg);
+                                    continue;
+                                }
+                            }
+                            None => {
+                                let (f, l) = (file!(), line!());
+                                let msg = format!(
+                                    "\
+                                    Error near {f}:{l}. The bitwidth for signal {name} \
+                                    must be specified for a signal of type {signal_type:?}. \
+                                    This error occurred while parsing the vcd file at \
+                                    {cursor:?}"
+                                );
+                                Err(msg)?;
+                            }
+                        };
+
+                        // record timestamp at which this event occurs
+                        lsb_indxs_of_string_tmstmp_vals_on_tmln
+                            .push(LsbIdxOfTmstmpValOnTmln(curr_tmstmp_lsb_idx));
+                        byte_len_of_string_tmstmp_vals_on_tmln.push(curr_tmstmp_len_u8);
+
+                        // record value
+                        string_vals.push(val);
+                        Ok(())
+                    }
+                    SignalEnum::Alias { .. } => {
+                        let (f, l) = (file!(), line!());
+                        let msg = format!(
+                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
+                             This error occurred while parsing vcd file at {cursor:?}");
+                        Err(msg)
+                    }
+                }?;
+            }
+            // Store real values as a string as well and let the user parse it to an f64
+            "s" | " S" | "r" | "R" => {
+                let val = word[1..].to_string();
+                let (hash, cursor) = next_word!(word_reader)?;
+                // lokup signal idx
+                let signal_idx = signal_map.get(hash).ok_or(()).map_err(|_| {
+                    format!(
+                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
+                        file!(),
+                        line!()
+                    )
+                })?;
+
+                let signal = vcd.dealiasing_signal_idx_to_signal_lookup_mut(signal_idx)?;
+
+                match signal {
+                    SignalEnum::Data {
+                        ref mut signal_error,
+                        string_vals,
+                        byte_len_of_string_tmstmp_vals_on_tmln,
+                        lsb_indxs_of_string_tmstmp_vals_on_tmln,
+                        ..
+                    } => {
+                        // if this is a bad signal, go ahead and skip it
+                        if signal_error.is_some() {
+                            continue;
+                        }
+
+                        // record timestamp at which this event occurs
+                        lsb_indxs_of_string_tmstmp_vals_on_tmln
+                            .push(LsbIdxOfTmstmpValOnTmln(curr_tmstmp_lsb_idx));
+                        byte_len_of_string_tmstmp_vals_on_tmln.push(curr_tmstmp_len_u8);
+
+                        // record string value
+                        string_vals.push(val);
+                        Ok(())
+                    }
+                    SignalEnum::Alias { .. } => {
+                        let (f, l) = (file!(), line!());
+                        let msg = format!(
+                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
+                             This error occurred while parsing vcd file at {cursor:?}");
+                        Err(msg)
+                    }
+                }?;
+            }
+            _ => {}
+        }
+    }
+
+    Ok(())
+}

src/vcd/parse/metadata.rs

@@ -0,0 +1,335 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use chrono::prelude::{DateTime, Utc};
+use itertools::Itertools;
+
+use super::super::reader::{next_word, Cursor, WordReader};
+use super::super::types::{Metadata, Timescale, Version};
+
+use super::combinator_atoms::{digit, tag, take_until, take_while};
+use super::types::ParseResult;
+
+pub(super) fn parse_date(
+    word_and_ctx1: (&str, &Cursor),
+    word_and_ctx2: (&str, &Cursor),
+    word_and_ctx3: (&str, &Cursor),
+    word_and_ctx4: (&str, &Cursor),
+    word_and_ctx5: (&str, &Cursor),
+) -> Result<DateTime<Utc>, String> {
+    let day = {
+        // check for another word in the file
+        let (word, cursor) = word_and_ctx1;
+
+        let days = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
+        if !days.contains(&word) {
+            let msg = format!("Error near {}:{}.", file!(), line!());
+            let msg2 = format!("{word} is not a valid weekday : expected one of {days:?}\n");
+            let msg3 = format!("failure location: {cursor:?}");
+            return Err(format!("{}{}{}", msg, msg2, msg3));
+        }
+
+        word.to_string()
+    };
+
+    let month = {
+        // check for another word in the file
+        let (word, cursor) = word_and_ctx2;
+
+        let months = [
+            "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sept", "Oct", "Nov", "Dec",
+        ];
+
+        if !months.contains(&word) {
+            let msg = format!("Error near {}:{}.", file!(), line!());
+            let msg2 = format!("{word} is not a valid month : expected one of {months:?}\n");
+            let msg3 = format!("failure location: {cursor:?}");
+            return Err(format!("{}{}{}", msg, msg2, msg3));
+        }
+
+        word.to_string()
+    };
+
+    let date = {
+        // check for another word in the file
+        let (word, cursor) = word_and_ctx3;
+
+        let date: u8 = match word.to_string().parse() {
+            Ok(date) => date,
+            Err(e) => return Err(format!("Error near {}:{}. {e}", file!(), line!())),
+        };
+
+        if date > 31 {
+            let msg = format!("Error near {}:{}.", file!(), line!());
+            let msg2 = format!("{word} is not a valid date : must be between 0 and 31\n");
+            let msg3 = format!("failure location: {cursor:?}");
+            return Err(format!("{}{}{}", msg, msg2, msg3));
+        }
+
+        date.to_string()
+    };
+
+    let (hh, mm, ss) = {
+        // get hour
+        let (word, cursor) = word_and_ctx4;
+
+        let res = take_until(word, b':');
+        res.assert_match()?;
+        let hh: u8 = res
+            .matched
+            .to_string()
+            .parse()
+            .map_err(|e| format!("Error near {}:{}. {e}", file!(), line!()))?;
+
+        if hh > 23 {
+            let msg = format!("Error near {}:{}.", file!(), line!());
+            let msg2 = format!("{hh} is not a valid hour : must be between 0 and 23\n");
+            let msg3 = format!("failure location: {cursor:?}");
+            return Err(format!("{}{}{}", msg, msg2, msg3));
+        }
+
+        // get minute
+        let word = &res.residual[1..]; // chop off colon which is at index 0
+        let res = take_until(word, b':');
+        res.assert_match()?;
+        let mm: u8 = res
+            .matched
+            .to_string()
+            .parse()
+            .map_err(|e| format!("Error near {}:{}. {e}", file!(), line!()))?;
+
+        if mm > 60 {
+            let msg = format!("Error near {}:{}.", file!(), line!());
+            let msg2 = format!("{mm} is not a valid minute : must be between 0 and 60\n");
+            let msg3 = format!("failure location: {cursor:?}");
+            return Err(format!("{}{}{}", msg, msg2, msg3));
+        }
+
+        // get second
+        // let ss : u8 = remainder.to_string().parse().unwrap();
+        res.assert_residual()?;
+        let residual = &res.residual[1..]; // chop of colon which is at index 0
+        let ss: u8 = residual
+            .to_string()
+            .parse()
+            .map_err(|e| format!("Error near {}:{}. {e}", file!(), line!()))?;
+
+        if ss > 60 {
+            let msg = format!("Error near {}:{}.", file!(), line!());
+            let msg2 = format!("{ss} is not a valid second : must be between 0 and 60\n");
+            let msg3 = format!("failure location: {cursor:?}");
+            return Err(format!("{}{}{}", msg, msg2, msg3));
+        }
+        (hh.to_string(), mm.to_string(), ss.to_string())
+    };
+
+    let year = {
+        // check for another word in the file
+        let (word, _) = word_and_ctx5;
+        word.to_string()
+    };
+
+    // unfortunately, the minutes, seconds, and hour could occur in an
+    // unexpected order
+    let full_date = format!("{day} {month} {date} {hh}:{mm}:{ss} {year}");
+    let full_date = DateTime::parse_from_str(full_date.as_str(), "%a %b %e %T %Y");
+    if full_date.is_ok() {
+        return Ok(full_date.unwrap().into());
+    }
+
+    Err(format!(
+        "Error near {}:{}. Failed to parse date.",
+        file!(),
+        line!()
+    ))
+}
+
+pub(super) fn parse_version<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+) -> Result<Version, String> {
+    let mut version = String::new();
+
+    loop {
+        let (word, _) = next_word!(word_reader)?;
+
+        if word == "$end" {
+            // truncate trailing whitespace
+            let version = version[0..(version.len() - 1)].to_string();
+            return Ok(Version(version));
+        } else {
+            version.push_str(word);
+            version.push(' ');
+        }
+    }
+}
+
+pub(super) fn parse_timescale<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+) -> Result<(Option<u32>, Timescale), String> {
+    // we might see `1ps $end` or `1 ps $end`
+    // first get timescale
+    let (word, _) = next_word!(word_reader)?;
+    let ParseResult { matched, residual } = take_while(word, digit);
+    let scalar = matched;
+
+    let scalar: u32 = scalar
+        .to_string()
+        .parse()
+        .map_err(|e| format!("Error near {}:{}. {e}", file!(), line!()))?;
+
+    let timescale = {
+        if residual.is_empty() {
+            let (word, _) = next_word!(word_reader)?;
+            let unit = match word {
+                "fs" => Ok(Timescale::Fs),
+                "ps" => Ok(Timescale::Ps),
+                "ns" => Ok(Timescale::Ns),
+                "us" => Ok(Timescale::Us),
+                "ms" => Ok(Timescale::Ms),
+                "s" => Ok(Timescale::S),
+                _ => Err(format!(
+                    "Error near {}:{}. Unknown unit {word}.",
+                    file!(),
+                    line!()
+                )),
+            }?;
+
+            (Some(scalar), unit)
+        } else {
+            let unit = match residual {
+                "fs" => Ok(Timescale::Fs),
+                "ps" => Ok(Timescale::Ps),
+                "ns" => Ok(Timescale::Ns),
+                "us" => Ok(Timescale::Us),
+                "ms" => Ok(Timescale::Ms),
+                "s" => Ok(Timescale::S),
+                _ => Err(format!(
+                    "Error near {}:{}. Unknown unit {residual}.",
+                    file!(),
+                    line!()
+                )),
+            }?;
+
+            (Some(scalar), unit)
+        }
+    };
+
+    // then check for the `$end` keyword
+    let (word, _) = next_word!(word_reader)?;
+    tag(word, "$end").assert_match()?;
+
+    Ok(timescale)
+}
+
+pub(super) fn parse_metadata<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+) -> Result<Metadata, String> {
+    let mut metadata = Metadata {
+        date: None,
+        version: None,
+        timescale: (None, Timescale::Unit),
+    };
+
+    loop {
+        // check for another word in the file
+        let (word, _) = next_word!(word_reader)?;
+
+        let ParseResult { matched, residual } = tag(word, "$");
+        match matched {
+            // we hope that this word stars with a `$`
+            "$" => {
+                match residual {
+                    "date" => {
+                        // a date is typically composed of the 5 following words which can
+                        // occur in any order:
+                        // {Day, Month, Date(number in month), hh:mm:ss, year}.
+                        // Thus, we must lookahead read the 5 next words, and try our date
+                        // parser on 5! = 120 permutations of the 5 words.
+                        //
+                        // It is also possible that within each permutation, the hours,
+                        // minutes, and seconds could be in an unusual order, which means
+                        // that we may search up to 6 different permutations oh hh::mm:ss,
+                        // for an upper bound total of 720 permutations
+                        //
+                        // While looking ahead, if one of the 5 words in `$end`, we have to
+                        // immediately stop trying to get more words.
+
+                        let mut found_end = false;
+                        let mut lookahead_5_words: Vec<(String, Cursor)> = Vec::new();
+
+                        for _ in 0..5 {
+                            let (word, cursor) = next_word!(word_reader)?;
+                            let word = word.to_string();
+                            match word.as_str() {
+                                "$end" => {
+                                    found_end = true;
+                                    break;
+                                }
+                                _ => {
+                                    lookahead_5_words.push((word, cursor));
+                                }
+                            };
+                        }
+
+                        // we no longer attempt to parse date if we weren't able to lookahead 5
+                        // words
+                        if found_end {
+                            continue;
+                        }
+
+                        let permutations = lookahead_5_words
+                            .iter()
+                            .permutations(lookahead_5_words.len());
+
+                        // go ahead and search for a match amongst permuted date text
+                        for mut permutations in permutations {
+                            let (w1, s1) = permutations.pop().unwrap();
+                            let arg_1 = (&w1[..], s1);
+
+                            let (w2, s2) = permutations.pop().unwrap();
+                            let arg_2 = (&w2[..], s2);
+
+                            let (w3, s3) = permutations.pop().unwrap();
+                            let arg_3 = (&w3[..], s3);
+
+                            let (w4, s4) = permutations.pop().unwrap();
+                            let arg_4 = (&w4[..], s4);
+
+                            let (w5, s5) = permutations.pop().unwrap();
+                            let arg_5 = (&w5[..], s5);
+
+                            let parsed_date = parse_date(arg_1, arg_2, arg_3, arg_4, arg_5);
+
+                            // store date and exit loop if a match is found
+                            if parsed_date.is_ok() {
+                                metadata.date = Some(parsed_date?);
+                                break;
+                            }
+                        }
+                    }
+                    "version" => {
+                        let version = parse_version(word_reader);
+                        if version.is_ok() {
+                            metadata.version = Some(version.unwrap());
+                        }
+                    }
+                    "timescale" => {
+                        let timescale = parse_timescale(word_reader);
+                        if timescale.is_ok() {
+                            metadata.timescale = timescale.unwrap();
+                        }
+                    }
+                    "scope" => break,
+                    "var" => break,
+                    // we keep searching for words until we've found one of the following
+                    // keywords, ["version", "timescale", "scope", "var"]
+                    _ => {}
+                }
+            }
+            // if word does not start with `$`, then we keep looping
+            _ => {}
+        }
+    }
+    Ok(metadata)
+}

src/vcd/parse/scopes.rs

@@ -0,0 +1,522 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+
+/// part of the vcd parser that handles parsing the signal tree and
+/// building the resulting signal tree
+use std::collections::HashMap;
+
+use super::super::reader::{curr_word, next_word, WordReader};
+use super::super::signal::{SignalEnum, SignalType};
+use super::super::types::{Scope, ScopeIdx, SignalIdx, VCD};
+
+use super::combinator_atoms::{ident, tag};
+use super::types::ParseResult;
+
+pub(super) fn parse_var<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+    parent_scope_idx: ScopeIdx,
+    vcd: &mut VCD,
+    signal_map: &mut HashMap<String, SignalIdx>,
+    path: &Vec<String>,
+) -> Result<(), String> {
+    let (word, cursor) = next_word!(word_reader)?;
+    let expected_types = [
+        "event",
+        "integer",
+        "parameter",
+        "real",
+        "realtime",
+        "reg",
+        "string",
+        "supply0",
+        "supply1",
+        "time",
+        "tri",
+        "triand",
+        "trior",
+        "trireg",
+        "tri0",
+        "tri1",
+        "wand",
+        "wire",
+        "wor",
+    ];
+
+    // $var parameter 3 a IDLE $end
+    //      ^^^^^^^^^ - var_type
+    let var_type = match word {
+        "event" => Ok(SignalType::Event),
+        "integer" => Ok(SignalType::Integer),
+        "parameter" => Ok(SignalType::Parameter),
+        "real" => Ok(SignalType::Real),
+        "realtime" => Ok(SignalType::RealTime),
+        "reg" => Ok(SignalType::Reg),
+        "string" => Ok(SignalType::Str),
+        "supply0" => Ok(SignalType::Supply0),
+        "supply1" => Ok(SignalType::Supply1),
+        "tri" => Ok(SignalType::Tri),
+        "triand" => Ok(SignalType::TriAnd),
+        "trior" => Ok(SignalType::TriOr),
+        "trireg" => Ok(SignalType::TriReg),
+        "tri0" => Ok(SignalType::Tri0),
+        "tri1" => Ok(SignalType::Tri1),
+        "time" => Ok(SignalType::Time),
+        "wand" => Ok(SignalType::WAnd),
+        "wire" => Ok(SignalType::Wire),
+        "wor" => Ok(SignalType::WOr),
+        _ => {
+            let err = format!(
+                "Error near {}:{} \
+                               found keyword `{word}` but expected one of \
+                               {expected_types:?} on {cursor:?}",
+                file!(),
+                line!()
+            );
+            Err(err)
+        }
+    }?;
+
+    let (word, cursor) = next_word!(word_reader)?;
+
+    let parse_err = format!("failed to parse as usize on {cursor:?}");
+
+    // $var parameter 3 a IDLE $end
+    //                ^ - num_bits
+    let num_bits = match var_type {
+        SignalType::Event
+        | SignalType::Integer
+        | SignalType::Parameter
+        | SignalType::Reg
+        | SignalType::Supply0
+        | SignalType::Supply1
+        | SignalType::Tri
+        | SignalType::TriAnd
+        | SignalType::TriOr
+        | SignalType::TriReg
+        | SignalType::Tri0
+        | SignalType::Tri1
+        | SignalType::Time
+        | SignalType::WAnd
+        | SignalType::Wire
+        | SignalType::WOr => {
+            let num_bits = word
+                .parse::<usize>()
+                .unwrap_or_else(|_| panic!("{}", parse_err));
+            let num_bits = u32::try_from(num_bits).map_err(|_| {
+                format!(
+                    "Error near {}:{} while parsing vcd file at {cursor:?}. \
+                     This signal has {num_bits} > 2^32 - 1 bits.",
+                    file!(),
+                    line!()
+                )
+            })?;
+            Some(num_bits)
+        }
+        // for strings, reals, and realtimes we don't really care what the number of bits is
+        _ => None,
+    };
+
+    // $var parameter 3 a IDLE $end
+    //                  ^ - signal_alias
+    let (word, _) = next_word!(word_reader)?;
+    let signal_alias = word.to_string();
+
+    // $var parameter 3 a IDLE $end
+    //                    ^^^^ - full_signal_name(can extend until $end)
+    let mut full_signal_name = Vec::<String>::new();
+    let mut size = None;
+    loop {
+        let (word, _) = next_word!(word_reader)?;
+        match word {
+            "$end" => break,
+            other if other.starts_with('[') => size = Some(other.to_string()),
+            _ => full_signal_name.push(word.to_string()),
+        }
+    }
+    let full_signal_name = full_signal_name.join(" ");
+
+    let num_bytes = if num_bits.is_some() {
+        let bytes_required = SignalEnum::bytes_required(num_bits.unwrap(), &full_signal_name)?;
+        Some(bytes_required)
+    } else {
+        None
+    };
+
+    // Is the current variable an alias to a signal already encountered?
+    // if so, handle ref_signal_idx accordingly, if not, add signal to hash
+    // map
+    let (signal, signal_idx) = match signal_map.get(&signal_alias) {
+        Some(ref_signal_idx) => {
+            let signal_idx = SignalIdx(vcd.all_signals.len());
+            let signal = SignalEnum::Alias {
+                name: full_signal_name.clone(),
+                path: path
+                    .iter()
+                    .cloned()
+                    .chain([full_signal_name])
+                    .collect::<Vec<String>>(),
+                signal_alias: *ref_signal_idx,
+            };
+            (signal, signal_idx)
+        }
+        None => {
+            let signal_idx = SignalIdx(vcd.all_signals.len());
+            signal_map.insert(signal_alias.to_string(), signal_idx);
+            let signal = SignalEnum::Data {
+                name: full_signal_name.clone(),
+                path: path
+                    .iter()
+                    .cloned()
+                    .chain([full_signal_name])
+                    .collect::<Vec<String>>(),
+                signal_type: var_type,
+                index: size,
+                signal_error: None,
+                num_bits,
+                num_bytes,
+                self_idx: signal_idx,
+                nums_encoded_as_fixed_width_le_u8: vec![],
+                string_vals: vec![],
+                lsb_indxs_of_num_tmstmp_vals_on_tmln: vec![],
+                byte_len_of_num_tmstmp_vals_on_tmln: vec![],
+                byte_len_of_string_tmstmp_vals_on_tmln: vec![],
+                lsb_indxs_of_string_tmstmp_vals_on_tmln: vec![],
+            };
+            (signal, signal_idx)
+        }
+    };
+
+    vcd.all_signals.push(signal);
+    let ScopeIdx(parent_scope_idx_usize) = parent_scope_idx;
+    let parent_scope = vcd.all_scopes.get_mut(parent_scope_idx_usize).unwrap();
+    parent_scope.child_signals.push(signal_idx);
+
+    Ok(())
+}
+
+/// Sometimes, variables can be listed outside of scopes.
+/// We call these orphaned vars.
+fn parse_orphaned_vars<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+    vcd: &mut VCD,
+    signal_map: &mut HashMap<String, SignalIdx>,
+) -> Result<(), String> {
+    // create scope for unscoped signals if such a scope does not
+    // yet exist
+    let scope_name = "Orphaned Signals";
+
+    // set default scope_idx to the count of existing scope as we
+    // generally set scope.self_idx to the number of existing scopes
+    // when that particular scope was inserted
+    let mut scope_idx = ScopeIdx(vcd.all_scopes.len());
+
+    // Override scope_idx if we find a scope named "Orphaned Signals"
+    // already exists
+    let mut scope_already_exists = false;
+    for scope in &vcd.all_scopes {
+        if scope.name == scope_name {
+            scope_idx = scope.self_idx;
+            scope_already_exists = true;
+            break;
+        }
+    }
+
+    if !scope_already_exists {
+        vcd.all_scopes.push(Scope {
+            name: scope_name.to_string(),
+            self_idx: scope_idx,
+            child_signals: vec![],
+            child_scopes: vec![],
+        });
+        vcd.root_scopes.push(scope_idx);
+    }
+
+    // we can go ahead and parse the current var as we've already encountered
+    // "$var" before now.
+    parse_var(word_reader, scope_idx, vcd, signal_map, &vec![])?;
+
+    loop {
+        let (word, cursor) = next_word!(word_reader)?;
+
+        match word {
+            "$var" => {
+                parse_var(word_reader, scope_idx, vcd, signal_map, &vec![])?;
+            }
+            "$scope" => break,
+            _ => {
+                let msg = format!(
+                    "Error near {}:{}.\
+                          Expected $scope or $var, found \
+                          {word} at {cursor:?}",
+                    file!(),
+                    line!()
+                );
+                Err(msg)?;
+            }
+        };
+    }
+
+    Ok(())
+}
+
+fn parse_scopes_inner<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+    parent_scope_idx: Option<ScopeIdx>,
+    vcd: &mut VCD,
+    signal_map: &mut HashMap<String, SignalIdx>,
+    path: &Vec<String>,
+) -> Result<(), String> {
+    // $scope module reg_mag_i $end
+    //        ^^^^^^ - module keyword
+    let (keyword, cursor) = next_word!(word_reader)?;
+
+    let expected = ["module", "begin", "task", "function", "fork"];
+    if expected.contains(&keyword) {
+        Ok(())
+    } else {
+        let err = format!(
+            "Error near {}:{}. \
+                            found keyword `{keyword}` but expected one of \
+                            {expected:?} on {cursor:?}",
+            file!(),
+            line!()
+        );
+        Err(err)
+    }?;
+
+    // $scope module reg_mag_i $end
+    //               ^^^^^^^^^ - scope name
+    let (scope_name, _) = next_word!(word_reader)?;
+    // In some cases there are VCD files which have scopes without names.
+    // since these occur in the wild, we'll tolerate them even if it is unclear
+    // if it is supported or not by the spec.
+    if scope_name != "$end" {
+        let mut path = path.clone();
+        path.push(scope_name.to_string());
+
+        let curr_scope_idx = ScopeIdx(vcd.all_scopes.len());
+
+        // register this scope as a child of the current parent scope
+        // if there is a parent scope, or else we register this scope as
+        // root scope
+        match parent_scope_idx {
+            Some(ScopeIdx(parent_scope_idx)) => {
+                let parent_scope = vcd.all_scopes.get_mut(parent_scope_idx).unwrap();
+                parent_scope.child_scopes.push(curr_scope_idx);
+            }
+            None => vcd.root_scopes.push(curr_scope_idx),
+        }
+
+        // add this scope to list of existing scopes
+        vcd.all_scopes.push(Scope {
+            name: scope_name.to_string(),
+            self_idx: curr_scope_idx,
+            child_signals: vec![],
+            child_scopes: vec![],
+        });
+
+        // $scope module reg_mag_i $end
+        //                         ^^^^ - end keyword
+        ident(word_reader, "$end")?;
+
+        loop {
+            let (word, cursor) = next_word!(word_reader)?;
+            let ParseResult { matched, residual } = tag(word, "$");
+            match matched {
+                // we hope that this word starts with a `$`
+                "$" => {
+                    match residual {
+                        "scope" => {
+                            // recursive - parse inside of current scope tree
+                            parse_scopes_inner(
+                                word_reader,
+                                Some(curr_scope_idx),
+                                vcd,
+                                signal_map,
+                                &path,
+                            )?;
+                        }
+                        "var" => {
+                            parse_var(word_reader, curr_scope_idx, vcd, signal_map, &path)?;
+                        }
+                        "upscope" => {
+                            ident(word_reader, "$end")?;
+                            break;
+                        }
+                        // we ignore comments
+                        "comment" => loop {
+                            if ident(word_reader, "$end").is_ok() {
+                                break;
+                            }
+                        },
+                        _ => {
+                            let err = format!(
+                                "Error near {}:{}. \
+                                               found keyword `{residual}` but expected \
+                                               `$scope`, `$var`, `$comment`, or `$upscope` \
+                                               on {cursor:?}",
+                                file!(),
+                                line!()
+                            );
+                            return Err(err);
+                        }
+                    }
+                }
+                _ => {
+                    let err = format!(
+                        "Error near {}:{}. \
+                                      found keyword `{matched}` but \
+                                      expected `$` on {cursor:?}",
+                        file!(),
+                        line!()
+                    );
+                    return Err(err);
+                }
+            }
+        }
+    } else {
+        // We'll be conservative and only allow new scopes in this case, and make the nameless
+        // scope completely transparent. I.e.
+        // $scope module a $end
+        //   $scope module $end
+        //     $scope module b $end
+        //       ...
+        //     $upscope
+        //   $upscope
+        // $upscope
+        // will create `a.b`
+        loop {
+            let (word, cursor) = next_word!(word_reader)?;
+            let ParseResult { matched, residual } = tag(word, "$");
+            match matched {
+                // we hope that this word starts with a `$`
+                "$" => {
+                    match residual {
+                        "scope" => {
+                            // recursive - parse inside of current scope tree
+                            parse_scopes_inner(
+                                word_reader,
+                                parent_scope_idx,
+                                vcd,
+                                signal_map,
+                                &path,
+                            )?;
+                        }
+                        "upscope" => {
+                            ident(word_reader, "$end")?;
+                            break;
+                        }
+                        // we ignore comments
+                        "comment" => loop {
+                            if ident(word_reader, "$end").is_ok() {
+                                break;
+                            }
+                        },
+                        _ => {
+                            let err = format!(
+                                "Error near {}:{}. \
+                                               found keyword `{residual}` in annonyoums scope but expected \
+                                               `$scope`, `$comment`, or `$upscope` \
+                                               on {cursor:?}",
+                                file!(),
+                                line!()
+                            );
+                            return Err(err);
+                        }
+                    }
+                }
+                _ => {
+                    let err = format!(
+                        "Error near {}:{}. \
+                                      found keyword `{matched}` but \
+                                      expected `$` on {cursor:?}",
+                        file!(),
+                        line!()
+                    );
+                    return Err(err);
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+
+pub(super) fn parse_scopes<R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
+    vcd: &mut VCD,
+    signal_map: &mut HashMap<String, SignalIdx>,
+) -> Result<(), String> {
+    // get the current word
+    let (word, _) = curr_word!(word_reader)?;
+
+    // we may have orphaned vars that occur before the first scope
+    if word == "$var" {
+        parse_orphaned_vars(word_reader, vcd, signal_map)?;
+    }
+
+    // get the current word
+    let (word, cursor) = curr_word!(word_reader)?;
+
+    // the current word should be "scope", as `parse_orphaned_vars`(if it
+    // was called), should have terminated upon encountering "$scope".
+    // If `parse_orphaned_vars` was not called, `parse_scopes` should still
+    // have only been called if the caller encountered the word "$scope"
+    if word != "$scope" {
+        let msg = format!(
+            "Error near {}:{}.\
+                           Expected $scope or $var, found \
+                           {word} at {cursor:?}",
+            file!(),
+            line!()
+        );
+        return Err(msg);
+    }
+
+    // now for the interesting part
+    parse_scopes_inner(word_reader, None, vcd, signal_map, &vec![])?;
+
+    // let err = format!("reached end of file without parser leaving {}", function_name!());
+    let expected_keywords = ["$scope", "$enddefinitions"];
+
+    // there could be multiple signal trees, and unfortunately, we
+    // can't merge the earlier call to `parse_scopes_inner` into this loop
+    // because this loop gets a word from `next_word` instead of
+    // `curr_word()`.
+    loop {
+        let (word, cursor) = next_word!(word_reader)?;
+
+        match word {
+            "$scope" => {
+                parse_scopes_inner(word_reader, None, vcd, signal_map, &vec![])?;
+            }
+            "$enddefinitions" => {
+                ident(word_reader, "$end")?;
+                break;
+            }
+            "$comment" => {
+                // although we don't store comments, we still need to advance the
+                // word_reader cursor to the end of the comment
+                loop {
+                    if ident(word_reader, "$end").is_ok() {
+                        break;
+                    }
+                }
+            }
+            _ => {
+                let err = format!(
+                    "Error near {}:{} \
+                                found keyword `{word}` but expected one of \
+                                {expected_keywords:?} on {cursor:?}",
+                    file!(),
+                    line!()
+                );
+                return Err(err);
+            }
+        }
+    }
+
+    Ok(())
+}

src/vcd/parse/types.rs

@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+#[derive(Debug)]
+pub(super) struct ParseResult<'a> {
+    pub(super) matched: &'a str,
+    pub(super) residual: &'a str,
+}
+
+impl<'a> ParseResult<'a> {
+    pub(super) fn assert_match(&self) -> Result<&str, String> {
+        if self.matched.is_empty() {
+            Err("no match".to_string())
+        } else {
+            Ok(self.matched)
+        }
+    }
+
+    pub(super) fn assert_residual(&self) -> Result<&str, String> {
+        if self.residual.is_empty() {
+            Err("no residual".to_string())
+        } else {
+            Ok(self.residual)
+        }
+    }
+}

src/vcd/reader.rs

@@ -0,0 +1,131 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use std::collections::VecDeque;
+use std::io;
+use std::io::BufRead;
+use std::slice;
+use std::str;
+
+#[derive(Debug, Clone)]
+pub(super) struct Line(pub(super) usize);
+#[derive(Debug, Clone)]
+pub(super) struct Word(pub(super) usize);
+#[derive(Debug, Clone)]
+pub(super) struct Cursor(pub(super) Line, pub(super) Word);
+
+pub(super) struct WordReader<R: io::Read> {
+    reader: io::BufReader<R>,
+    eof: bool,
+    buffers: Vec<String>,
+    curr_line: usize,
+    str_slices: VecDeque<(*const u8, usize, Cursor)>,
+    curr_slice: Option<(*const u8, usize, Cursor)>,
+}
+
+impl<R: std::io::Read> WordReader<R> {
+    pub(super) fn new(file: R) -> WordReader<R> {
+        let reader = io::BufReader::new(file);
+        WordReader {
+            reader,
+            eof: false,
+            buffers: vec![],
+            curr_line: 0,
+            str_slices: VecDeque::new(),
+            curr_slice: None,
+        }
+    }
+
+    pub(super) fn next_word(&mut self) -> Option<(&str, Cursor)> {
+        // although reaching the eof is not technically an error, in most cases,
+        // we treat it like one in the rest of the codebase.
+
+        // if there are no more words in the buffer, attempt to read more content
+        // from the file
+        if self.str_slices.is_empty() {
+            self.buffers.clear();
+
+            if self.eof {
+                return None;
+            }
+
+            let num_buffers = 10;
+
+            for buf_idx in 0..num_buffers {
+                self.buffers.push(String::new());
+                self.curr_line += 1;
+                let bytes_read = self.reader.read_line(&mut self.buffers[buf_idx]).unwrap();
+
+                // if we've reached the end of the file on the first attempt to read
+                // a line in this for loop, no further attempts are necessary and we
+                if bytes_read == 0 {
+                    self.eof = true;
+                    break;
+                }
+
+                let words = self.buffers[buf_idx].split_ascii_whitespace();
+
+                for word in words.enumerate() {
+                    let (word_idx, word) = word;
+                    let position = Cursor(Line(self.curr_line), Word(word_idx + 1));
+                    self.str_slices
+                        .push_back((word.as_ptr(), word.len(), position))
+                }
+            }
+        }
+
+        // if after we've attempted to read in more content from the file,
+        // there are still no words...
+        if self.str_slices.is_empty() {
+            return None;
+        }
+
+        // if we make it here, we return the next word
+        unsafe {
+            let (ptr, len, position) = self.str_slices.pop_front().unwrap();
+            let slice = slice::from_raw_parts(ptr, len);
+            self.curr_slice = Some((ptr, len, position.clone()));
+            return Some((str::from_utf8(slice).unwrap(), position));
+        };
+    }
+
+    pub(super) fn curr_word(&mut self) -> Option<(&str, Cursor)> {
+        match &self.curr_slice {
+            Some(slice) => unsafe {
+                let (ptr, len, position) = slice.clone();
+                let slice = slice::from_raw_parts(ptr, len);
+                return Some((str::from_utf8(slice).unwrap(), position));
+            },
+            None => None,
+        }
+    }
+}
+
+macro_rules! next_word {
+    ($word_reader:ident) => {
+        $word_reader.next_word().ok_or(()).map_err(|_| {
+            format!(
+                "Error near {}:{}. Did not expect to reach end of file here.",
+                file!(),
+                line!()
+            )
+        })
+    };
+}
+
+macro_rules! curr_word {
+    ($word_reader:ident) => {
+        $word_reader.curr_word().ok_or(()).map_err(|_| {
+            format!(
+                "Error near {}:{}. A call to curr_word! shouldn't \
+                 fail unless next_word has not yet been invoked.",
+                file!(),
+                line!()
+            )
+        })
+    };
+}
+
+pub(super) use curr_word;
+pub(super) use next_word;

src/vcd/signal.rs

@@ -0,0 +1,715 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use super::types;
+use super::types::SignalIdx;
+use num::BigUint;
+
+// Index to the least significant byte of a timestamp
+// value on the timeline
+#[derive(Debug, Copy, Clone)]
+pub struct LsbIdxOfTmstmpValOnTmln(pub(super) u32);
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub enum SignalType {
+    Event,
+    Integer,
+    Parameter,
+    Real,
+    RealTime,
+    Reg,
+    Str,
+    Supply0,
+    Supply1,
+    Time,
+    Tri,
+    TriAnd,
+    TriOr,
+    TriReg,
+    Tri0,
+    Tri1,
+    WAnd,
+    Wire,
+    WOr,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum SignalValue {
+    BigUint(BigUint),
+    String(String),
+}
+
+pub struct QueryResult<T> {
+    pub current: Option<(TimeStamp, T)>,
+    pub next: Option<TimeStamp>,
+}
+
+pub struct Signal<'a>(pub(super) &'a SignalEnum);
+
+impl<'a> Signal<'a> {
+    pub fn name(&self) -> String {
+        let Signal(signal_enum) = &self;
+        signal_enum.name()
+    }
+
+    pub fn name_with_index(&self) -> String {
+        let Signal(signal_enum) = &self;
+        signal_enum.name_with_index()
+    }
+
+    pub fn index(&self) -> Option<String> {
+        let Signal(signal_enum) = &self;
+        signal_enum.index()
+    }
+
+    pub fn path(&self) -> &[String] {
+        match self.0 {
+            SignalEnum::Data { path, .. } => path,
+            SignalEnum::Alias { path, .. } => path,
+        }
+    }
+
+    pub fn signal_type(&self) -> Option<&SignalType> {
+        let Signal(signal_enum) = &self;
+        signal_enum.signal_type()
+    }
+
+    pub fn real_idx(&self) -> SignalIdx {
+        match self.0 {
+            SignalEnum::Data { self_idx, .. } => *self_idx,
+            SignalEnum::Alias { signal_alias, .. } => *signal_alias,
+        }
+    }
+
+    pub fn num_bits(&self) -> Option<u32> {
+        let Signal(signal_enum) = &self;
+        signal_enum.bits_required()
+    }
+
+    // NOTE: (zoq) I am removing thse because they aren't used in Surfer so I can't test them
+    // properly
+    /*
+    pub fn query_string_val_on_tmln(
+        &self,
+        desired_time: &BigUint,
+        vcd: &types::VCD,
+    ) -> Result<String, SignalErrors> {
+        let Signal(signal_enum) = &self;
+        signal_enum
+            .query_string_val_on_tmln(desired_time, &vcd.tmstmps_encoded_as_u8s, &vcd.all_signals)
+            .map(|QueryResult{current, next: _}| current.map(|c| c.1))
+    }
+
+    pub fn query_num_val_on_tmln(
+        &self,
+        desired_time: &BigUint,
+        vcd: &types::VCD,
+    ) -> Result<Option<BigUint>, SignalErrors> {
+        let Signal(signal_enum) = &self;
+        signal_enum
+            .query_num_val_on_tmln(desired_time, &vcd.tmstmps_encoded_as_u8s, &vcd.all_signals)
+            .map(|QueryResult{current, next: _}| current.map(|c| c.1))
+    }
+    */
+
+    pub fn query_val_on_tmln(
+        &self,
+        desired_time: &BigUint,
+        vcd: &types::VCD,
+    ) -> Result<QueryResult<SignalValue>, SignalErrors> {
+        let Signal(signal_enum) = &self;
+        let num_query_out = signal_enum.query_num_val_on_tmln(
+            desired_time,
+            &vcd.tmstmps_encoded_as_u8s,
+            &vcd.all_signals,
+        );
+        let str_query_out = signal_enum.query_string_val_on_tmln(
+            desired_time,
+            &vcd.tmstmps_encoded_as_u8s,
+            &vcd.all_signals,
+        );
+
+        // Both num and str will return the newest value that is closest to
+        // the desired time. If both have valid values, select the most recent
+        // one
+        match (num_query_out, str_query_out) {
+            (Ok(num_result), Ok(str_result)) => {
+                let next = match (num_result.next, str_result.next) {
+                    (Some(n), Some(s)) => Some(n.min(s)),
+                    (Some(n), None) => Some(n),
+                    (None, Some(s)) => Some(s),
+                    (None, None) => None,
+                };
+
+                match (num_result.current, str_result.current) {
+                    (Some((num_time, num_value)), Some((str_time, str_value))) => {
+                        if num_time > str_time {
+                            Ok(QueryResult {
+                                current: Some((num_time, SignalValue::BigUint(num_value))),
+                                next,
+                            })
+                        } else {
+                            Ok(QueryResult {
+                                current: Some((str_time, SignalValue::String(str_value))),
+                                next,
+                            })
+                        }
+                    }
+                    (Some((num_time, num_val)), None) => Ok(QueryResult {
+                        current: Some((num_time, SignalValue::BigUint(num_val))),
+                        next,
+                    }),
+                    (None, Some((str_time, str_value))) => Ok(QueryResult {
+                        current: Some((str_time, SignalValue::String(str_value))),
+                        next,
+                    }),
+                    (None, None) => Ok(QueryResult {
+                        current: None,
+                        next,
+                    }),
+                }
+            }
+            (_e, Err(e)) => Err(e),
+            (Err(e), _e) => Err(e),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(super) enum SignalEnum {
+    Data {
+        name: String,
+        path: Vec<String>,
+        signal_type: SignalType,
+        /// The optional [start:end] part of the signal name that is sometimes
+        /// added to signals
+        index: Option<String>,
+        /// I've seen a 0 bit signal parameter in a xilinx
+        /// simulation before that gets assigned 1 bit values.
+        /// I consider this to be bad behavior. We capture such
+        /// errors in the following type:
+        signal_error: Option<String>,
+        num_bits: Option<u32>,
+        num_bytes: Option<u16>,
+        /// TODO : may be able to remove self_idx
+        self_idx: SignalIdx,
+        /// A signal may take on a new value and hold that value
+        /// for sometime. We only need to record the value of a signal
+        /// when it changes(the is what VCDs tend to do).
+        /// A signal may need x amount of bytes to record its largest
+        /// possible value, so we record every single value of a given
+        /// signal as a sequence of x number of u8s.
+        /// For example, we might find that `my_signal.
+        /// nums_encoded_as_fixed_width_le_u8`
+        /// has two 32 bit values, namely, 1 and 2, encoded as follows:
+        /// my_signal.nums_encoded_as_fixed_width_le_u8 = vec![1u8, 0u8,
+        /// 0u8, 0u8, 2u8, 0u8, 0u8, 0u8];
+        nums_encoded_as_fixed_width_le_u8: Vec<u8>,
+        string_vals: Vec<String>,
+        /// we could do Vec<(LsbIdxOfTmstmpValOnTmln, u8)>, but I
+        /// suspect that Vec<LsbIdxOfTmstmpValOnTmln> is more cache
+        /// friendly. We use ``LsbIdxOfTmstmpValOnTmln`` to index into
+        /// the LSB of a particular timestamp encoded as the
+        /// minimum length u8 sequence within
+        /// ``vcd.tmstmps_encoded_as_u8s``, and we use the values in
+        /// ``byte_len_of_num_tmstmp_vals_on_tmln`` to determine how
+        /// many u8 values a particular timestamp is composed of.
+        lsb_indxs_of_num_tmstmp_vals_on_tmln: Vec<LsbIdxOfTmstmpValOnTmln>,
+        byte_len_of_num_tmstmp_vals_on_tmln: Vec<u8>,
+        byte_len_of_string_tmstmp_vals_on_tmln: Vec<u8>,
+        lsb_indxs_of_string_tmstmp_vals_on_tmln: Vec<LsbIdxOfTmstmpValOnTmln>,
+    },
+    Alias {
+        name: String,
+        path: Vec<String>,
+        signal_alias: SignalIdx,
+    },
+}
+
+#[derive(Debug)]
+pub enum SignalErrors {
+    EmptyTimeline,
+    TimelineNotMultiple,
+    StrTmlnLenMismatch,
+    OrderingFailure {
+        lhs_time: BigUint,
+        mid_time: BigUint,
+        rhs_time: BigUint,
+    },
+    PointsToAlias,
+    NoNumBytes,
+    Other(String),
+}
+
+// these are thin type aliases primarily to make code more readable later on
+type TimeStamp = BigUint;
+type SignalValNum = BigUint;
+
+// getter functions
+impl SignalEnum {
+    pub fn name(&self) -> String {
+        match self {
+            SignalEnum::Data { name, .. } => name,
+            SignalEnum::Alias { name, .. } => name,
+        }
+        .clone()
+    }
+
+    pub fn signal_type(&self) -> Option<&SignalType> {
+        match self {
+            SignalEnum::Data { signal_type, .. } => Some(signal_type),
+            // TODO: Follow aliases?
+            SignalEnum::Alias { .. } => None,
+        }
+        .clone()
+    }
+
+    pub fn name_with_index(&self) -> String {
+        match self {
+            SignalEnum::Data {
+                name, index: None, ..
+            } => format!("{name}"),
+            SignalEnum::Data {
+                name,
+                index: Some(size),
+                ..
+            } => format!("{name} {size}"),
+            SignalEnum::Alias { name, .. } => name.clone(),
+        }
+    }
+
+    pub fn index(&self) -> Option<String> {
+        match self {
+            SignalEnum::Data { index, .. } => index.clone(),
+            SignalEnum::Alias { .. } => None,
+        }
+    }
+}
+
+// helper functions ultimately used by Signal's query functions later on
+impl SignalEnum {
+    /// Computes the bytes required to store a signal's numerical value
+    /// using the num_bits which another function would provide from
+    /// the num_bits field of the Signal::Data variant.
+    pub(super) fn bytes_required(num_bits: u32, name: &String) -> Result<u16, String> {
+        let bytes_required = (num_bits / 8) + if (num_bits % 8) > 0 { 1 } else { 0 };
+        let bytes_required = u16::try_from(bytes_required).map_err(|_| {
+            format!(
+                "Error near {}:{}. Signal {name} of length num_bits requires \
+                        {bytes_required} > 65536 bytes.",
+                file!(),
+                line!()
+            )
+        })?;
+        Ok(bytes_required)
+    }
+    /// This function takes an event_idx which(is used to index into the
+    /// global timeline field of a VCD struct instance) and computes
+    /// the time pointed at by event_idx.
+    /// This function also uses the same idx to index into the
+    /// string_vals field of an instance of the Signal::Data variant
+    ///  and gets a string value.
+    /// The function returns a tuple of the timestamp and string value.
+    fn time_and_str_val_at_event_idx(
+        &self,
+        event_idx: usize,
+        tmstmps_encoded_as_u8s: &Vec<u8>,
+    ) -> Result<(TimeStamp, &str), SignalErrors> {
+        let (
+            string_vals,
+            lsb_indxs_of_string_tmstmp_vals_on_tmln,
+            byte_len_of_string_tmstmp_vals_on_tmln,
+        ) = match self {
+            SignalEnum::Data {
+                string_vals,
+                lsb_indxs_of_string_tmstmp_vals_on_tmln,
+                byte_len_of_string_tmstmp_vals_on_tmln,
+                ..
+            } => Ok((
+                string_vals,
+                lsb_indxs_of_string_tmstmp_vals_on_tmln,
+                byte_len_of_string_tmstmp_vals_on_tmln,
+            )),
+            SignalEnum::Alias { .. } => Err(SignalErrors::PointsToAlias),
+        }?;
+
+        // get index
+        let LsbIdxOfTmstmpValOnTmln(timestamp_idx) =
+            lsb_indxs_of_string_tmstmp_vals_on_tmln[event_idx];
+        let timestamp_idx = timestamp_idx as usize;
+
+        if byte_len_of_string_tmstmp_vals_on_tmln.is_empty() {
+            return Err(SignalErrors::EmptyTimeline);
+        }
+
+        // form timestamp
+        let byte_len = byte_len_of_string_tmstmp_vals_on_tmln[event_idx] as usize;
+        let timestamp = &tmstmps_encoded_as_u8s[timestamp_idx..(timestamp_idx + byte_len)];
+        let timestamp = BigUint::from_bytes_le(timestamp);
+
+        // get signal value
+        let signal_val = string_vals[event_idx].as_str();
+
+        Ok((timestamp, signal_val))
+    }
+    /// This function takes an event_idx which(is used to index into the
+    /// global timeline field of a VCD struct instance) and computes
+    /// the time pointed at by event_idx.
+    /// This function also uses the same idx to index into the
+    /// nums_encoded_as_fixed_width_le_u8 and
+    /// byte_len_of_num_tmstmp_vals_on_tmln fields of an instance
+    /// of the Signal::Data variant to compute the signal's corresponding
+    /// numerical value at the time pointed at by event_didx.
+    /// The function returns a tuple of the timestamp and numerical
+    /// value.
+    fn time_and_num_val_at_event_idx(
+        &self,
+        event_idx: usize,
+        tmstmps_encoded_as_u8s: &Vec<u8>,
+    ) -> Result<(TimeStamp, SignalValNum), SignalErrors> {
+        let (
+            num_bytes,
+            nums_encoded_as_fixed_width_le_u8,
+            lsb_indxs_of_num_tmstmp_vals_on_tmln,
+            byte_len_of_num_tmstmp_vals_on_tmln,
+        ) = match self {
+            SignalEnum::Data {
+                num_bytes,
+                nums_encoded_as_fixed_width_le_u8,
+                lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                byte_len_of_num_tmstmp_vals_on_tmln,
+                ..
+            } => Ok((
+                num_bytes,
+                nums_encoded_as_fixed_width_le_u8,
+                lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                byte_len_of_num_tmstmp_vals_on_tmln,
+            )),
+            SignalEnum::Alias { .. } => Err(SignalErrors::PointsToAlias),
+        }?;
+
+        // get index
+        let LsbIdxOfTmstmpValOnTmln(timestamp_idx) =
+            lsb_indxs_of_num_tmstmp_vals_on_tmln[event_idx];
+        let timestamp_idx = timestamp_idx as usize;
+
+        // form timestamp
+        let byte_len = byte_len_of_num_tmstmp_vals_on_tmln[event_idx] as usize;
+        let timestamp = &tmstmps_encoded_as_u8s[timestamp_idx..(timestamp_idx + byte_len)];
+        let timestamp = BigUint::from_bytes_le(timestamp);
+
+        // get signal value
+        let bytes_per_value = num_bytes.ok_or_else(|| SignalErrors::NoNumBytes)?;
+        let bytes_per_value = bytes_per_value as usize;
+        let start_idx = event_idx * bytes_per_value;
+        let end_idx = (event_idx + 1) * bytes_per_value;
+        let signal_val = &nums_encoded_as_fixed_width_le_u8[start_idx..end_idx];
+        let signal_val = BigUint::from_bytes_le(signal_val);
+
+        Ok((timestamp, signal_val))
+    }
+
+    fn bits_required(&self) -> Option<u32> {
+        match self {
+            SignalEnum::Data { num_bits, .. } => *num_bits,
+            // TODO: Follow aliases?
+            SignalEnum::Alias { .. } => None,
+        }
+    }
+}
+
+// Val and string query functions.
+// Function that take in a desired time on the timeline for a
+// specific signal and return a numerical or string value in a Result,
+// or an error in a Result.
+impl SignalEnum {
+    pub fn query_string_val_on_tmln(
+        &self,
+        desired_time: &BigUint,
+        tmstmps_encoded_as_u8s: &Vec<u8>,
+        all_signals: &Vec<SignalEnum>,
+    ) -> Result<QueryResult<String>, SignalErrors> {
+        let signal_idx = match self {
+            Self::Data { self_idx, .. } => {
+                let SignalIdx(idx) = self_idx;
+                *idx
+            }
+            Self::Alias {
+                name: _,
+                signal_alias,
+                path: _,
+            } => {
+                let SignalIdx(idx) = signal_alias;
+                *idx
+            }
+        };
+
+        // if the signal idx points to data variant of the signal,
+        // extract:
+        // 1. the vector of string values
+        // 2. the vector of indices into timeline where events occur
+        //    for this signal
+        // else we propagate Err(..).
+        let (string_vals, lsb_indxs_of_string_tmstmp_vals_on_tmln) = match &all_signals[signal_idx]
+        {
+            SignalEnum::Data {
+                ref string_vals,
+                ref lsb_indxs_of_string_tmstmp_vals_on_tmln,
+                ..
+            } => Ok((string_vals, lsb_indxs_of_string_tmstmp_vals_on_tmln)),
+            SignalEnum::Alias { .. } => Err(SignalErrors::PointsToAlias),
+        }?;
+        // this signal should at least have some events, otherwise, trying to index into
+        // an empty vector later on would fail
+        if lsb_indxs_of_string_tmstmp_vals_on_tmln.is_empty() {
+            return Ok(QueryResult {
+                current: None,
+                next: None
+            });
+        }
+
+        // the vector of string timeline lsb indices should have the same
+        // length as the vector of string values
+        if string_vals.len() != lsb_indxs_of_string_tmstmp_vals_on_tmln.len() {
+            return Err(SignalErrors::StrTmlnLenMismatch);
+        }
+
+        // check if we're requesting a value that occurs before the recorded
+        // start of the timeline
+        let (timeline_start_time, _) =
+            self.time_and_str_val_at_event_idx(0, tmstmps_encoded_as_u8s)?;
+        if *desired_time < timeline_start_time {
+            return Ok(QueryResult {
+                current: None,
+                next: Some(timeline_start_time),
+            });
+        }
+
+        let mut lower_idx = 0usize;
+        let mut upper_idx = lsb_indxs_of_string_tmstmp_vals_on_tmln.len() - 1;
+        let (timeline_end_time, timeline_end_val) =
+            self.time_and_str_val_at_event_idx(upper_idx, tmstmps_encoded_as_u8s)?;
+
+        // check if we're requesting a value that occurs beyond the end of the timeline,
+        // if so, return the last value in this timeline
+        if *desired_time > timeline_end_time {
+            return Ok(QueryResult {
+                current: Some((timeline_end_time, timeline_end_val.to_string())),
+                next: None,
+            });
+        }
+
+        // This while loop is the meat of the lookup. Performance is log2(n),
+        // where n is the number of events on the timeline.
+        // We can assume that by the time we get here, that the desired_time
+        // is an event that occurs on the timeline, given that we handle any events
+        // occuring after or before the recorded tiimeline in the code above.
+        while lower_idx <= upper_idx {
+            let mid_idx = lower_idx + ((upper_idx - lower_idx) / 2);
+            let (curr_time, curr_val) =
+                self.time_and_str_val_at_event_idx(mid_idx, tmstmps_encoded_as_u8s)?;
+            let ordering = curr_time.cmp(desired_time);
+
+            match ordering {
+                std::cmp::Ordering::Less => {
+                    lower_idx = mid_idx + 1;
+                }
+                std::cmp::Ordering::Equal => {
+                    let next_time = if mid_idx < lsb_indxs_of_string_tmstmp_vals_on_tmln.len() - 1 {
+                        Some(
+                            self.time_and_str_val_at_event_idx(
+                                mid_idx + 1,
+                                tmstmps_encoded_as_u8s,
+                            )?
+                            .0,
+                        )
+                    } else {
+                        None
+                    };
+                    return Ok(QueryResult {
+                        current: Some((curr_time, curr_val.to_string())),
+                        next: next_time,
+                    });
+                }
+                std::cmp::Ordering::Greater => {
+                    upper_idx = mid_idx - 1;
+                }
+            }
+        }
+
+        let (left_time, left_val) =
+            self.time_and_str_val_at_event_idx(lower_idx - 1, tmstmps_encoded_as_u8s)?;
+        let (right_time, _) =
+            self.time_and_str_val_at_event_idx(lower_idx, tmstmps_encoded_as_u8s)?;
+
+        let ordered_left = left_time < *desired_time;
+        let ordered_right = *desired_time < right_time;
+        if !(ordered_left && ordered_right) {
+            return Err(SignalErrors::OrderingFailure {
+                lhs_time: left_time,
+                mid_time: desired_time.clone(),
+                rhs_time: right_time,
+            });
+        }
+
+        Ok(QueryResult {
+            current: Some((left_time, left_val.to_string())),
+            next: Some(right_time),
+        })
+    }
+    pub fn query_num_val_on_tmln(
+        &self,
+        desired_time: &BigUint,
+        tmstmps_encoded_as_u8s: &Vec<u8>,
+        all_signals: &Vec<SignalEnum>,
+    ) -> Result<QueryResult<BigUint>, SignalErrors> {
+        let signal_idx = match self {
+            Self::Data { self_idx, .. } => {
+                let SignalIdx(idx) = self_idx;
+                *idx
+            }
+            Self::Alias {
+                name: _,
+                path: _,
+                signal_alias,
+            } => {
+                let SignalIdx(idx) = signal_alias;
+                *idx
+            }
+        };
+
+        // if the signal idx points to data variant of the signal,
+        // extract:
+        // 1. the vector of LE u8 compressed values
+        // 2. the vector of indices into timeline where events occur
+        //    for this signal
+        // 3. the number of bytes per value for this signal
+        // else we propagate Err(..).
+        let (nums_encoded_as_fixed_width_le_u8, lsb_indxs_of_num_tmstmp_vals_on_tmln, num_bytes) =
+            match &all_signals[signal_idx] {
+                SignalEnum::Data {
+                    num_bytes,
+                    ref nums_encoded_as_fixed_width_le_u8,
+                    ref lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                    ..
+                } => {
+                    if num_bytes.is_none() {
+                        return Err(SignalErrors::NoNumBytes);
+                    }
+                    Ok((
+                        nums_encoded_as_fixed_width_le_u8,
+                        lsb_indxs_of_num_tmstmp_vals_on_tmln,
+                        num_bytes,
+                    ))
+                }
+                SignalEnum::Alias { .. } => Err(SignalErrors::PointsToAlias),
+            }?;
+        // this signal should at least have some events, otherwise, trying to index into
+        // an empty vector later on would fail
+        if lsb_indxs_of_num_tmstmp_vals_on_tmln.is_empty() {
+            return Ok(QueryResult {
+                current: None,
+                next: None
+            });
+        }
+
+        // assertion that value_sequence is a proper multiple of
+        // timeline_markers
+        let bytes_required = num_bytes.ok_or_else(|| {
+            SignalErrors::Other(format!(
+                "Error near {}:{}. num_bytes empty.",
+                file!(),
+                line!()
+            ))
+        })?;
+        if nums_encoded_as_fixed_width_le_u8.len()
+            != (lsb_indxs_of_num_tmstmp_vals_on_tmln.len() * (bytes_required as usize))
+        {
+            return Err(SignalErrors::TimelineNotMultiple);
+        }
+
+        // check if we're requesting a value that occurs before the recorded
+        // start of the timeline
+        let (timeline_start_time, _) =
+            self.time_and_num_val_at_event_idx(0, tmstmps_encoded_as_u8s)?;
+        if *desired_time < timeline_start_time {
+            return Ok(QueryResult {
+                current: None,
+                next: Some(timeline_start_time),
+            });
+        }
+
+        let mut lower_idx = 0usize;
+        let mut upper_idx = lsb_indxs_of_num_tmstmp_vals_on_tmln.len() - 1;
+        let (timeline_end_time, timeline_end_val) =
+            self.time_and_num_val_at_event_idx(upper_idx, tmstmps_encoded_as_u8s)?;
+
+        // check if we're requesting a value that occurs beyond the end of the timeline,
+        // if so, return the last value in this timeline
+        if *desired_time > timeline_end_time {
+            return Ok(QueryResult {
+                current: Some((timeline_end_time, timeline_end_val)),
+                next: None,
+            });
+        }
+
+        // This while loop is the meat of the lookup. Performance is log2(n),
+        // where n is the number of events on the timeline.
+        // We can assume that by the time we get here, that the desired_time
+        // is an event that occurs on the timeline, given that we handle any events
+        // occuring after or before the recorded tiimeline in the code above.
+        while lower_idx <= upper_idx {
+            let mid_idx = lower_idx + ((upper_idx - lower_idx) / 2);
+            let (curr_time, curr_val) =
+                self.time_and_num_val_at_event_idx(mid_idx, tmstmps_encoded_as_u8s)?;
+            let ordering = curr_time.cmp(desired_time);
+
+            match ordering {
+                std::cmp::Ordering::Less => {
+                    lower_idx = mid_idx + 1;
+                }
+                std::cmp::Ordering::Equal => {
+                    let next_time = if mid_idx < lsb_indxs_of_num_tmstmp_vals_on_tmln.len() - 1 {
+                        Some(
+                            self.time_and_num_val_at_event_idx(
+                                mid_idx + 1,
+                                tmstmps_encoded_as_u8s,
+                            )?
+                            .0,
+                        )
+                    } else {
+                        None
+                    };
+                    return Ok(QueryResult {
+                        current: Some((curr_time, curr_val)),
+                        next: next_time,
+                    });
+                }
+                std::cmp::Ordering::Greater => {
+                    upper_idx = mid_idx - 1;
+                }
+            }
+        }
+
+        let (left_time, left_val) =
+            self.time_and_num_val_at_event_idx(lower_idx - 1, tmstmps_encoded_as_u8s)?;
+        let (right_time, _) =
+            self.time_and_num_val_at_event_idx(lower_idx, tmstmps_encoded_as_u8s)?;
+
+        let ordered_left = left_time < *desired_time;
+        let ordered_right = *desired_time < right_time;
+        if !(ordered_left && ordered_right) {
+            return Err(SignalErrors::OrderingFailure {
+                lhs_time: left_time,
+                mid_time: desired_time.clone(),
+                rhs_time: right_time,
+            });
+        }
+
+        return Ok(QueryResult {
+            current: Some((left_time, left_val)),
+            next: Some(right_time),
+        });
+    }
+}

src/vcd/types.rs

@@ -0,0 +1,144 @@
+// use crate::Signal;
+
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use super::signal::{Signal, SignalEnum};
+use chrono::prelude::{DateTime, Utc};
+use num::BigUint;
+use std::fmt;
+
+#[derive(Debug, Clone)]
+pub struct Version(pub String);
+
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+pub enum Timescale {
+    Fs,
+    Ps,
+    Ns,
+    Us,
+    Ms,
+    S,
+    Unit,
+}
+
+impl fmt::Display for Timescale {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Timescale::Fs => write!(f, "fs"),
+            Timescale::Ps => write!(f, "ps"),
+            Timescale::Ns => write!(f, "ns"),
+            Timescale::Us => write!(f, "μs"),
+            Timescale::Ms => write!(f, "ms"),
+            Timescale::S => write!(f, "s"),
+            Timescale::Unit => write!(f, "unit"),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Metadata {
+    pub date: Option<DateTime<Utc>>,
+    pub version: Option<Version>,
+    pub timescale: (Option<u32>, Timescale),
+}
+
+// We do a lot of arena allocation in this codebase.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct ScopeIdx(pub usize);
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct SignalIdx(pub usize);
+
+#[derive(Debug)]
+pub(super) struct Scope {
+    pub(super) name: String,
+
+    pub(super) self_idx: ScopeIdx,
+
+    pub(super) child_signals: Vec<SignalIdx>,
+    pub(super) child_scopes: Vec<ScopeIdx>,
+}
+
+#[derive(Debug)]
+pub struct VCD {
+    pub metadata: Metadata,
+    // Since we only need to store values when there is an actual change
+    // in the timeline, we keep a vector that stores the time at which an
+    // event occurs. Time t is always stored/encoded as the minimum length sequence
+    // of u8.
+    // We essentially fill ``tmstmps_encoded_as_u8s`` with BigUints converted
+    // to sequences of little endian u8s.
+    // It is up to the signals to keep track of the start/stop indices in the
+    // vector of u8s that constitute a timestamp value. Signals don't have to
+    // keep track of all timestamp values, a given signal only needs to keep
+    // track of the timestamps at which the given signal value changes.
+    pub(super) tmstmps_encoded_as_u8s: Vec<u8>,
+    pub(super) all_signals: Vec<SignalEnum>,
+    pub(super) all_scopes: Vec<Scope>,
+    pub(super) root_scopes: Vec<ScopeIdx>,
+    pub(super) largest_timestamp: Option<BigUint>,
+}
+
+impl VCD {
+    pub fn root_scopes_by_idx(&self) -> Vec<ScopeIdx> {
+        self.root_scopes.clone()
+    }
+    pub fn child_scopes_by_idx(&self, scope_idx: ScopeIdx) -> Vec<ScopeIdx> {
+        let ScopeIdx(idx) = scope_idx;
+        let scope = &self.all_scopes[idx];
+        scope.child_scopes.clone()
+    }
+    pub fn get_children_signal_idxs(&self, scope_idx: ScopeIdx) -> Vec<SignalIdx> {
+        let ScopeIdx(idx) = scope_idx;
+        let scope = &self.all_scopes[idx];
+        scope.child_signals.clone()
+    }
+    pub fn scope_name_by_idx(&self, scope_idx: ScopeIdx) -> &String {
+        let ScopeIdx(idx) = scope_idx;
+        let scope = &self.all_scopes[idx];
+        &scope.name
+    }
+    pub fn signal_from_signal_idx(&self, idx: SignalIdx) -> Signal<'_> {
+        let SignalIdx(idx) = idx;
+        let signal_enum = &self.all_signals[idx];
+        return Signal(signal_enum);
+    }
+    /// We take in a Signal and attempt to de-alias that signal if it is of
+    /// variant ``Signal::Alias``. If it is of variant ``Signal::Alias`` and points to
+    /// another alias, that's an error. Otherwise, we return the ``Signal::Data``
+    /// pointed to by the ``Signal::Alias``.
+    /// If the Signal is of varint ``Signal::Data``, then that can be returned directly.
+    pub(super) fn dealiasing_signal_idx_to_signal_lookup_mut<'a>(
+        &'a mut self,
+        idx: &SignalIdx,
+    ) -> Result<&'a mut SignalEnum, String> {
+        // get the signal pointed to be SignalIdx from the arena
+        let SignalIdx(idx) = idx;
+        let signal = &self.all_signals[*idx];
+
+        // dereference signal if Signal::Alias, or keep idx if Signal::Data
+        let signal_idx = match signal {
+            SignalEnum::Data { self_idx, .. } => *self_idx,
+            SignalEnum::Alias { signal_alias, .. } => *signal_alias,
+        };
+
+        // Should now  point to Signal::Data variant, or else there's an error
+        let SignalIdx(idx) = signal_idx;
+        let signal = self.all_signals.get_mut(idx).unwrap();
+        match signal {
+            SignalEnum::Data { .. } => Ok(signal),
+            SignalEnum::Alias { .. } => Err(format!(
+                "Error near {}:{}. A signal alias shouldn't \
+                 point to a signal alias.",
+                file!(),
+                line!()
+            )),
+        }
+    }
+
+    pub fn max_timestamp(&self) -> &Option<BigUint> {
+        &self.largest_timestamp
+    }
+}

src/vcd/utilities.rs

@@ -0,0 +1,86 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+#[derive(Debug)]
+pub(super) enum BinaryParserErrTypes {
+    XValue,
+    ZValue,
+    UValue,
+    HValue,
+    LValue,
+    DashValue,
+    WValue,
+    OtherValue(char),
+    TooLong,
+}
+
+// We build a quick and not so dirty bit string parser.
+fn base2_str_to_byte(word: &[u8]) -> Result<u8, BinaryParserErrTypes> {
+    let mut val = 0u8;
+
+    // shouldn't have more than 8 chars in str
+    let len = word.len();
+    if len > 8 {
+        return Err(BinaryParserErrTypes::TooLong);
+    }
+
+    let bit_lut = [
+        0b0000_0001u8,
+        0b0000_0010u8,
+        0b0000_0100u8,
+        0b0000_1000u8,
+        0b0001_0000u8,
+        0b0010_0000u8,
+        0b0100_0000u8,
+        0b1000_0000u8,
+    ];
+
+    for (idx, chr) in word.iter().rev().enumerate() {
+        match chr {
+            b'1' => val |= bit_lut[idx],
+            b'0' => {}
+            b'x' | b'X' => return Err(BinaryParserErrTypes::XValue),
+            b'z' | b'Z' => return Err(BinaryParserErrTypes::ZValue),
+            b'u' | b'U' => return Err(BinaryParserErrTypes::UValue),
+            b'l' | b'L' => return Err(BinaryParserErrTypes::LValue),
+            b'h' | b'H' => return Err(BinaryParserErrTypes::HValue),
+            b'w' | b'W' => return Err(BinaryParserErrTypes::WValue),
+            b'-' => return Err(BinaryParserErrTypes::DashValue),
+            _ => return Err(BinaryParserErrTypes::OtherValue(*chr as char)),
+        }
+    }
+
+    Ok(val)
+}
+
+pub(super) fn binary_str_to_vec_u8(binary_str: &str) -> Result<Vec<u8>, BinaryParserErrTypes> {
+    let mut vec_u8: Vec<u8> = Vec::new();
+    let binary_str_as_bytes = binary_str.as_bytes();
+
+    let mut tail_idx = binary_str_as_bytes.len();
+    // clamp head if provided binary str is less than 8 long
+    let mut head_idx = if tail_idx >= 8 {
+        binary_str_as_bytes.len() - 8
+    } else {
+        0
+    };
+    while tail_idx > 0 {
+        let curr_b_val = &binary_str_as_bytes[head_idx..tail_idx];
+        let val_u8 = base2_str_to_byte(curr_b_val)?;
+        vec_u8.push(val_u8);
+
+        if head_idx < 8 {
+            head_idx = 0
+        } else {
+            head_idx -= 8;
+        }
+
+        if tail_idx < 8 {
+            tail_idx = 0
+        } else {
+            tail_idx -= 8;
+        }
+    }
+    Ok(vec_u8)
+}

test-vcd-files/sources.csv

@@ -1,4 +0,0 @@
-Icarus,Verilator,GHDL,VCS,QuestaSim,ModelSim,Quartus,SystemC,Treadle,Aldec,Riviera-PRO,MyHDL,ncsim,xilinx_isim,vivado,GTKWave-Analyzer
-https://github.com/dpretet/vcd/blob/master/test1.vcd,https://github.com/wavedrom/vcd-samples/blob/trunk/swerv1.vcd,https://raw.githubusercontent.com/AdoobII/idea_21s/main/vhdl/idea.vcd,https://raw.githubusercontent.com/ameyjain/8-bit-Microprocessor/master/8-bit%20microprocessor/processor.vcd,https://github.com/mr-gaurav/Sequence-Counter/blob/main/test.vcd,https://github.com/Mohammad-Heydariii/Digital-Systems-Lab-Course/blob/main/Lab_project4/modelsim_files/clkdiv2n_tb.vcd,https://github.com/PedroTLemos/ProjetoInfraHard/blob/master/mipsHardware.vcd,https://github.com/jroslindo/Mips-Systemc/blob/main/REGISTRADORES_32_bits/wave_registradores.vcd,https://github.com/chipsalliance/treadle/blob/master/src/test/resources/GCD.vcd,https://github.com/SVeilleux9/FPGA-GPIO-Extender/blob/main/Firmware/aldec/SPI_Write/SPI_Write.vcd,https://github.com/prathampathak/Tic-Tac-Tao/blob/main/dump.vcd,https://github.com/aibtw/myHdl_Projects/blob/main/SimpleMemory/Simple_Memory.vcd,https://github.com/amiteee78/RTL_design/blob/master/ffdiv_32bit/ffdiv_32bit_prop_binom/run_cad/ffdiv_32bit_tb.vcd,https://github.com/mukul54/qrs-peak-fpga/blob/master/utkarsh/utkarsh.sim/sim_1/behav/xsim/test.vcd,https://github.com/saharmalmir/Eth2Ser/blob/master/UART2ETH.runs/impl_1/iladata.vcd,https://github.com/Asfagus/Network-Switch/blob/main/perm_current.vcd
-https://github.com/ombhilare999/riscv-core/blob/master/src/rv32_soc_TB.vcd,https://github.com/bigBrain1901/nPOWER-ISA-5-STAGE-PIPELINED-CPU/blob/master/post_compile_files/vlt_dump.vcd,https://github.com/gaoqqt2n/CPU/blob/master/SuperPipelineCPU/vcdfile/pcpu.vcd,https://raw.githubusercontent.com/Akashay-Singla/RISC-V/main/Pipeline/datapath_log.vcd,https://github.com/SparshAgarwal/Computer-Architecture/blob/master/hw3/hw3_1/dump.vcd,https://github.com/sh619/Songyu_Huang-Chisel/blob/main/MU0_final_version/simulation/qsim/CPU_Design.msim.vcd,,https://github.com/amrhas/PDRNoC/blob/VCRouter/noctweak/Debug/waveform.vcd.vcd,,,,https://github.com/Abhishek010397/Programming-RISC-V/blob/master/top.vcd,,https://github.com/DanieleParravicini/regex_coprocessor/blob/master/scripts/sim/test2x2_regex22_string1.vcd,https://github.com/BradMcDanel/multiplication-free-dnn/blob/master/verilog/iladata.vcd,
-https://github.com/b06902044/computer_architecture/blob/main/CPU.vcd,,https://github.com/charlycop/VLSI-1/blob/master/EXEC/ALU/alu.vcd,https://raw.githubusercontent.com/sathyapriyanka/APB_UVC_UVM/main/Apb_slave_uvm_new.vcd,,,,,,,,https://github.com/DarthSkipper/myHDL_Sigmoid/blob/master/out/testbench/sigmoid_tb.vcd,,https://github.com/pabloec1729/Hashes-generator/blob/master/RTL/velocidad/test.vcd,,

tests/files.rs

@@ -0,0 +1,77 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+
+// TODO: we should eventually be able to only test on just
+// the files const
+pub const FILES: [&str; 31] = [
+    "./tests/vcd-files/aldec/SPI_Write.vcd",
+    "./tests/vcd-files/ghdl/alu.vcd",
+    "./tests/vcd-files/ghdl/idea.vcd",
+    "./tests/vcd-files/ghdl/pcpu.vcd",
+    "./tests/vcd-files/gtkwave-analyzer/perm_current.vcd",
+    "./tests/vcd-files/icarus/CPU.vcd",
+    "./tests/vcd-files/icarus/rv32_soc_TB.vcd",
+    "./tests/vcd-files/icarus/test1.vcd",
+    "./tests/vcd-files/model-sim/CPU_Design.msim.vcd",
+    "./tests/vcd-files/model-sim/clkdiv2n_tb.vcd",
+    "./tests/vcd-files/my-hdl/Simple_Memory.vcd",
+    "./tests/vcd-files/my-hdl/sigmoid_tb.vcd",
+    "./tests/vcd-files/my-hdl/top.vcd",
+    "./tests/vcd-files/ncsim/ffdiv_32bit_tb.vcd",
+    "./tests/vcd-files/quartus/mipsHardware.vcd",
+    "./tests/vcd-files/quartus/wave_registradores.vcd",
+    "./tests/vcd-files/questa-sim/dump.vcd",
+    "./tests/vcd-files/questa-sim/test.vcd",
+    "./tests/vcd-files/riviera-pro/dump.vcd",
+    "./tests/vcd-files/systemc/waveform.vcd",
+    "./tests/vcd-files/treadle/GCD.vcd",
+    "./tests/vcd-files/vcs/Apb_slave_uvm_new.vcd",
+    "./tests/vcd-files/vcs/datapath_log.vcd",
+    "./tests/vcd-files/vcs/processor.vcd",
+    "./tests/vcd-files/verilator/swerv1.vcd",
+    "./tests/vcd-files/verilator/vlt_dump.vcd",
+    "./tests/vcd-files/vivado/iladata.vcd",
+    "./tests/vcd-files/xilinx_isim/test.vcd",
+    "./tests/vcd-files/xilinx_isim/test1.vcd",
+    // TODO : add signal ignore list to handle bitwidth mismatches
+    "./tests/vcd-files/xilinx_isim/test2x2_regex22_string1.vcd",
+    "./tests/vcd-files/scope_with_comment.vcd",
+];
+
+pub const GOOD_DATE_FILES: [&str; 24] = [
+    "./test-vcd-files/aldec/SPI_Write.vcd",
+    "./test-vcd-files/ghdl/alu.vcd",
+    "./test-vcd-files/ghdl/idea.vcd",
+    "./test-vcd-files/ghdl/pcpu.vcd",
+    "./test-vcd-files/gtkwave-analyzer/perm_current.vcd",
+    "./test-vcd-files/icarus/CPU.vcd",
+    "./test-vcd-files/icarus/rv32_soc_TB.vcd",
+    "./test-vcd-files/icarus/test1.vcd",
+    "./test-vcd-files/model-sim/CPU_Design.msim.vcd",
+    "./test-vcd-files/model-sim/clkdiv2n_tb.vcd",
+    "./test-vcd-files/my-hdl/Simple_Memory.vcd",
+    "./test-vcd-files/my-hdl/sigmoid_tb.vcd",
+    "./test-vcd-files/my-hdl/top.vcd",
+    "./test-vcd-files/questa-sim/dump.vcd",
+    "./test-vcd-files/questa-sim/test.vcd",
+    "./test-vcd-files/riviera-pro/dump.vcd",
+    "./test-vcd-files/vcs/Apb_slave_uvm_new.vcd",
+    "./test-vcd-files/vcs/datapath_log.vcd",
+    "./test-vcd-files/vcs/processor.vcd",
+    "./test-vcd-files/verilator/swerv1.vcd",
+    "./test-vcd-files/verilator/vlt_dump.vcd",
+    "./test-vcd-files/xilinx_isim/test.vcd",
+    "./test-vcd-files/xilinx_isim/test1.vcd",
+    "./test-vcd-files/xilinx_isim/test2x2_regex22_string1.vcd",
+];
+
+pub const BAD_DATE_FILES: [&str; 6] = [
+    "./test-vcd-files/ncsim/ffdiv_32bit_tb.vcd",
+    "./test-vcd-files/quartus/mipsHardware.vcd",
+    "./test-vcd-files/quartus/wave_registradores.vcd",
+    "./test-vcd-files/systemc/waveform.vcd",
+    "./test-vcd-files/treadle/GCD.vcd",
+    "./test-vcd-files/vivado/iladata.vcd",
+];

tests/integration_test.rs

@@ -0,0 +1,22 @@
+// Copyright (C) 2022 Yehowshua Immanuel
+// This program is distributed under both the GPLV3 license
+// and the YEHOWSHUA license, both of which can be found at
+// the root of the folder containing the sources for this program.
+use std::fs::File;
+
+mod files;
+use files::*;
+
+#[test]
+fn parse_all_VCDs() {
+    // see if we can parse all signal trees successfully
+    for file_name in FILES {
+        let file = File::open(file_name).unwrap();
+        let vcd = fastwave_backend::parse_vcd(file);
+
+        if !vcd.is_ok() {
+            dbg!(file_name);
+            vcd.unwrap();
+        }
+    }
+}

tests/vcd-files/VCD_file_with_errors.vcd

@@ -0,0 +1,92 @@
+$date
+Thu Dec 17 17:19:03 2020
+$end
+$version
+Aldec HDL Simulator Version 10.03.3558
+$end
+$timescale
+1 ps
+$end
+
+$scope module tb $end
+
+$scope module t $end
+$var wire 1 ! CLK $end
+$var wire 1 " LED $end
+$var wire 1 # PIN_10 $end
+$var wire 1 $ PIN_11 $end
+$var wire 1 % PIN_12 $end
+$var wire 1 & PIN_13 $end
+$var wire 1 ' SPI_In $end
+$var wire 1 ( SPI_Out $end
+$var wire 1 ) SPI_Data_Available $end
+$var wire 1 * RegMap_In $end
+$var wire 1 + RegMap_Out $end
+$var wire 1 , RegMap_Data_Available $end
+$var wire 8 - AddrBus [7:0] $end
+$var wire 8 . DataBus [7:0] $end
+
+$scope module controller $end
+$var wire 1 ! clk $end
+$var wire 1 " LED $end
+$var wire 8 . DataBus [7:0] $end
+$var wire 1 ) SPI_Data_Available $end
+$var wire 1 , RegMap_Data_available $end
+$var wire 8 / addr [7:0] $end
+$var wire 8 0 data [7:0] $end
+$var wire 1 1 BusActive $end
+$var reg 8 2 AddrBus [7:0] $end
+$var reg 1 3 SPI_In $end
+$var reg 1 4 SPI_Out $end
+$var reg 1 5 RegMap_In $end
+$var reg 1 6 RegMap_Out $end
+$var reg 1 7 LED_state $end
+$var reg 3 8 block [2:0] $end
+$var reg 3 9 doing [2:0] $end
+$var parameter 3 : IDLE $end
+$var parameter 3 ; READ_ADDR $end
+$var parameter 3 < READ_DATA $end
+$var parameter 3 = TX $end
+$var parameter 3 > SPI $end
+$upscope $end
+
+
+$scope module reg_mag_i $end
+$var wire 1 ! clk $end
+$var wire 1 + RegMap_Out $end
+$var wire 1 * RegMap_In $end
+$var wire 8 - AddrBus [7:0] $end
+$var wire 8 . DataBus [7:0] $end
+$var wire 1 ? r_w $end
+$var wire 1 @ outputData $end
+$var wire 1 A inputData $end
+$var reg 1 B RegMap_Data_Available $end
+$var reg 8 C inData [7:0] $end
+$var reg 8 D inAddr [7:0] $end
+$var reg 8 E outData [7:0] $end
+$var reg 1 F addr_rcv $end
+$var reg 1 G data_rcv $end
+$var reg 2 H state [1:0] $end
+$var parameter 2 I INIT $end
+$var parameter 2 J IDLE $end
+$var parameter 2 K RX $end
+$var parameter 2 L TX $end
+$var parameter 32 M MAXADDRESS $end
+$upscope $end
+
+
+$scope module SPI_i $end
+$var wire 1 ! clk $end
+$var wire 1 # SCK $end
+$var wire 1 $ SSEL $end
+$var wire 1 % MOSI $end
+$var wire 1 & MISO $end
+$var wire 1 ' SPI_In $end
+$var wire 1 ( SPI_Out $end
+$var wire 8 - AddrBus [7:0] $end
+$var wire 8 . DataBus [7:0] $end
+$var wire 1 N SCK_risingedge $end
+$var wire 1 O SCK_fallingedge $end
+$var wire 1 P SSEL_active $end
+$var wire 1 Q MOSI_data $end
+$var reg 1 R SPI_Data_Available $end

tests/vcd-files/amaranth/up_counter.vcd

@@ -0,0 +1,287 @@
+$comment Generated by Amaranth $end
+$date 2022-07-13 18:48:57.685239 $end
+$timescale 1 ps $end
+$scope module bench $end
+$scope module top $end
+$var wire 1 ! clk $end
+$var wire 1 " rst $end
+$var wire 1 # ovf $end
+$var wire 16 $ count $end
+$var string 1 % state $end
+$var wire 1 & en $end
+$upscope $end
+$upscope $end
+$enddefinitions $end
+#0
+$dumpvars
+0!
+0"
+0#
+b0 $
+sTOP/0 %
+0&
+$end
+#500000
+1!
+#1000000
+0!
+#1500000
+1!
+#2000000
+0!
+#2500000
+1!
+#3000000
+0!
+#3500000
+1!
+#4000000
+0!
+#4500000
+1!
+#5000000
+0!
+#5500000
+1!
+#6000000
+0!
+#6500000
+1!
+#7000000
+0!
+#7500000
+1!
+#8000000
+0!
+#8500000
+1!
+#9000000
+0!
+#9500000
+1!
+#10000000
+0!
+#10500000
+1!
+#11000000
+0!
+#11500000
+1!
+#12000000
+0!
+#12500000
+1!
+#13000000
+0!
+#13500000
+1!
+#14000000
+0!
+#14500000
+1!
+#15000000
+0!
+#15500000
+1!
+#16000000
+0!
+#16500000
+1!
+#17000000
+0!
+#17500000
+1!
+#18000000
+0!
+#18500000
+1!
+#19000000
+0!
+#19500000
+1!
+#20000000
+0!
+#20500000
+1!
+#21000000
+0!
+#21500000
+1!
+#22000000
+0!
+#22500000
+1!
+#23000000
+0!
+#23500000
+1!
+#24000000
+0!
+#24500000
+1!
+#25000000
+0!
+#25500000
+1!
+#26000000
+0!
+#26500000
+1!
+#27000000
+0!
+#27500000
+1!
+#28000000
+0!
+#28500000
+1!
+#29000000
+0!
+#29500000
+1!
+#30000000
+0!
+#30500000
+1&
+1!
+#31000000
+0!
+#31500000
+sBOTTOM/2 %
+b1 $
+1!
+#32000000
+0!
+#32500000
+b10 $
+1!
+#33000000
+0!
+#33500000
+b11 $
+1!
+#34000000
+0!
+#34500000
+b100 $
+1!
+#35000000
+0!
+#35500000
+b101 $
+1!
+#36000000
+0!
+#36500000
+b110 $
+1!
+#37000000
+0!
+#37500000
+b111 $
+1!
+#38000000
+0!
+#38500000
+b1000 $
+1!
+#39000000
+0!
+#39500000
+b1001 $
+1!
+#40000000
+0!
+#40500000
+b1010 $
+1!
+#41000000
+0!
+#41500000
+b1011 $
+1!
+#42000000
+0!
+#42500000
+b1100 $
+1!
+#43000000
+0!
+#43500000
+b1101 $
+1!
+#44000000
+0!
+#44500000
+b1110 $
+1!
+#45000000
+0!
+#45500000
+b1111 $
+1!
+#46000000
+0!
+#46500000
+b10000 $
+1!
+#47000000
+0!
+#47500000
+b10001 $
+1!
+#48000000
+0!
+#48500000
+b10010 $
+1!
+#49000000
+0!
+#49500000
+b10011 $
+1!
+#50000000
+0!
+#50500000
+b10100 $
+1!
+#51000000
+0!
+#51500000
+b10101 $
+1!
+#52000000
+0!
+#52500000
+b10110 $
+1!
+#53000000
+0!
+#53500000
+b10111 $
+1!
+#54000000
+0!
+#54500000
+b11000 $
+1!
+#55000000
+0!
+#55500000
+1#
+b11001 $
+1!
+#56000000
+0!
+#56500000
+sTOP/0 %
+0#
+b0 $
+1!
+#57000000
+0!
+#57500000
+sBOTTOM/2 %
+b1 $
+1!
+#58000000

tests/vcd-files/scope_with_comment.vcd

@@ -0,0 +1,296 @@
+$date
+	Sat Dec 26 15:33:14 2020
+$end
+$version
+	ModelSim Version 10.5b
+$end
+$timescale
+	1ns
+$end
+
+$scope module clkdiv2n_tb $end
+$comment foo $end
+$var reg 1 ! clk $end
+$var reg 1 " reset $end
+$var wire 1 # clk_out $end
+
+$scope module t1 $end
+$var parameter 32 $ WIDTH $end
+$var parameter 32 % N $end
+$var wire 1 & clk $end
+$var wire 1 ' reset $end
+$var wire 1 # clk_out $end
+$var reg 3 ( r_reg [2:0] $end
+$var wire 1 ) r_nxt [2] $end
+$var wire 1 * r_nxt [1] $end
+$var wire 1 + r_nxt [0] $end
+$var reg 1 , clk_track $end
+$upscope $end
+$comment foo $end
+$upscope $end
+$comment foo $end
+$enddefinitions $end
+#0
+$comment foo $end
+$dumpvars
+0!
+x"
+bx (
+x,
+b11 $
+b110 %
+x#
+x+
+x*
+x)
+x'
+0&
+$end
+#5
+1"
+1'
+b0 (
+0,
+1+
+0*
+0)
+0#
+#10
+1!
+1&
+#15
+0"
+0'
+#20
+0!
+0&
+#30
+1!
+1&
+b1 (
+0+
+1*
+#40
+0!
+0&
+#50
+1!
+1&
+b10 (
+1+
+#60
+0!
+0&
+#70
+1!
+1&
+b11 (
+0+
+0*
+1)
+#80
+0!
+0&
+#90
+1!
+1&
+b100 (
+1+
+#100
+0!
+0&
+#110
+1!
+1&
+b101 (
+0+
+1*
+#120
+0!
+0&
+#130
+1!
+1&
+b0 (
+1,
+1+
+0*
+0)
+1#
+#140
+0!
+0&
+#150
+1!
+1&
+b1 (
+0+
+1*
+#160
+0!
+0&
+#170
+1!
+1&
+b10 (
+1+
+#180
+0!
+0&
+#190
+1!
+1&
+b11 (
+0+
+0*
+1)
+#200
+0!
+0&
+#210
+1!
+1&
+b100 (
+1+
+#220
+0!
+0&
+#230
+1!
+1&
+b101 (
+0+
+1*
+#240
+0!
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tests/vcd-files/sources.csv

@@ -0,0 +1,17 @@
+Icarus,https://github.com/dpretet/vcd/blob/master/test1.vcd,https://github.com/ombhilare999/riscv-core/blob/master/src/rv32_soc_TB.vcd,https://github.com/b06902044/computer_architecture/blob/main/CPU.vcd
+Verilator,https://github.com/wavedrom/vcd-samples/blob/trunk/swerv1.vcd,https://github.com/bigBrain1901/nPOWER-ISA-5-STAGE-PIPELINED-CPU/blob/master/post_compile_files/vlt_dump.vcd,
+GHDL,https://raw.githubusercontent.com/AdoobII/idea_21s/main/vhdl/idea.vcd,https://github.com/gaoqqt2n/CPU/blob/master/SuperPipelineCPU/vcdfile/pcpu.vcd,https://github.com/charlycop/VLSI-1/blob/master/EXEC/ALU/alu.vcd
+VCS,https://raw.githubusercontent.com/ameyjain/8-bit-Microprocessor/master/8-bit%20microprocessor/processor.vcd,https://raw.githubusercontent.com/Akashay-Singla/RISC-V/main/Pipeline/datapath_log.vcd,https://raw.githubusercontent.com/sathyapriyanka/APB_UVC_UVM/main/Apb_slave_uvm_new.vcd
+QuestaSim,https://github.com/mr-gaurav/Sequence-Counter/blob/main/test.vcd,https://github.com/SparshAgarwal/Computer-Architecture/blob/master/hw3/hw3_1/dump.vcd,
+ModelSim,https://github.com/Mohammad-Heydariii/Digital-Systems-Lab-Course/blob/main/Lab_project4/modelsim_files/clkdiv2n_tb.vcd,https://github.com/sh619/Songyu_Huang-Chisel/blob/main/MU0_final_version/simulation/qsim/CPU_Design.msim.vcd,
+Quartus,https://github.com/PedroTLemos/ProjetoInfraHard/blob/master/mipsHardware.vcd,,
+SystemC,https://github.com/jroslindo/Mips-Systemc/blob/main/REGISTRADORES_32_bits/wave_registradores.vcd,https://github.com/amrhas/PDRNoC/blob/VCRouter/noctweak/Debug/waveform.vcd.vcd,
+Treadle,https://github.com/chipsalliance/treadle/blob/master/src/test/resources/GCD.vcd,,
+Aldec,https://github.com/SVeilleux9/FPGA-GPIO-Extender/blob/main/Firmware/aldec/SPI_Write/SPI_Write.vcd,,
+Riviera-PRO,https://github.com/prathampathak/Tic-Tac-Tao/blob/main/dump.vcd,,
+MyHDL,https://github.com/aibtw/myHdl_Projects/blob/main/SimpleMemory/Simple_Memory.vcd,https://github.com/Abhishek010397/Programming-RISC-V/blob/master/top.vcd,https://github.com/DarthSkipper/myHDL_Sigmoid/blob/master/out/testbench/sigmoid_tb.vcd
+ncsim,https://github.com/amiteee78/RTL_design/blob/master/ffdiv_32bit/ffdiv_32bit_prop_binom/run_cad/ffdiv_32bit_tb.vcd,,
+xilinx_isim,https://github.com/mukul54/qrs-peak-fpga/blob/master/utkarsh/utkarsh.sim/sim_1/behav/xsim/test.vcd,https://github.com/DanieleParravicini/regex_coprocessor/blob/master/scripts/sim/test2x2_regex22_string1.vcd,https://github.com/pabloec1729/Hashes-generator/blob/master/RTL/velocidad/test.vcd
+vivado,https://github.com/saharmalmir/Eth2Ser/blob/master/UART2ETH.runs/impl_1/iladata.vcd,https://github.com/BradMcDanel/multiplication-free-dnn/blob/master/verilog/iladata.vcd,
+GTKWave-Analyzer,https://github.com/Asfagus/Network-Switch/blob/main/perm_current.vcd,,
+Amaranth,Locally Simulated File,,