diff --git a/src/vcd/parse.rs b/src/vcd/parse.rs
index 4a5e3b0..ef2ec61 100644
--- a/src/vcd/parse.rs
+++ b/src/vcd/parse.rs
@@ -11,7 +11,7 @@ mod scopes;
 mod events;
 
 
-pub fn parse_vcd(file: File) -> Result<super::types::VCD, String> {
+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)?;
diff --git a/src/vcd/parse/combinator_atoms.rs b/src/vcd/parse/combinator_atoms.rs
index 0473f63..c599f71 100644
--- a/src/vcd/parse/combinator_atoms.rs
+++ b/src/vcd/parse/combinator_atoms.rs
@@ -69,7 +69,10 @@ pub(super) fn tag<'a>(word: &'a str, pattern: &'a str) -> ParseResult<'a> {
     };
 }
 
-pub(super) fn ident(word_reader: &mut WordReader, keyword: &str) -> Result<(), String> {
+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)?;
 
diff --git a/src/vcd/parse/events.rs b/src/vcd/parse/events.rs
index 49bff94..2246d15 100644
--- a/src/vcd/parse/events.rs
+++ b/src/vcd/parse/events.rs
@@ -12,8 +12,8 @@ use super::super::reader::{WordReader, Cursor, Line, Word, next_word};
 use super::super::types::{SignalIdx, VCD};
 
 
-pub(super) fn parse_events<'a>(
-    word_reader: &mut WordReader,
+pub(super) fn parse_events<'a, R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
     vcd: &'a mut VCD,
     signal_map: &mut HashMap<String, SignalIdx>,
 ) -> Result<(), String> {
diff --git a/src/vcd/parse/metadata.rs b/src/vcd/parse/metadata.rs
index 6d0fffc..b908403 100644
--- a/src/vcd/parse/metadata.rs
+++ b/src/vcd/parse/metadata.rs
@@ -145,7 +145,7 @@ pub(super) fn parse_date(
     ))
 }
 
-pub(super) fn parse_version(word_reader: &mut WordReader) -> Result<Version, String> {
+pub(super) fn parse_version<R: std::io::Read>(word_reader: &mut WordReader<R>) -> Result<Version, String> {
     let mut version = String::new();
 
     loop {
@@ -162,8 +162,8 @@ pub(super) fn parse_version(word_reader: &mut WordReader) -> Result<Version, Str
     }
 }
 
-pub(super) fn parse_timescale(
-    word_reader: &mut WordReader,
+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
@@ -220,7 +220,7 @@ pub(super) fn parse_timescale(
     return Ok(timescale);
 }
 
-pub(super) fn parse_metadata(word_reader: &mut WordReader) -> Result<Metadata, String> {
+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,
diff --git a/src/vcd/parse/scopes.rs b/src/vcd/parse/scopes.rs
index cb193cf..00a087e 100644
--- a/src/vcd/parse/scopes.rs
+++ b/src/vcd/parse/scopes.rs
@@ -15,8 +15,8 @@ use super::super::signal::{SigType, SignalEnum};
 use super::combinator_atoms::{tag, ident};
 use super::types::{ParseResult};
 
-pub(super) fn parse_var<'a>(
-    word_reader: &mut WordReader,
+pub(super) fn parse_var<'a, R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
     parent_scope_idx: ScopeIdx,
     vcd: &'a mut VCD,
     signal_map: &mut HashMap<String, SignalIdx>,
@@ -157,8 +157,8 @@ pub(super) fn parse_var<'a>(
 
 /// Sometimes, variables can be listed outside of scopes.
 /// We call these orphaned vars.
-fn parse_orphaned_vars<'a>(
-    word_reader: &mut WordReader,
+fn parse_orphaned_vars<'a, R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
     vcd: &'a mut VCD,
     signal_map: &mut HashMap<String, SignalIdx>,
 ) -> Result<(), String> {
@@ -221,8 +221,8 @@ fn parse_orphaned_vars<'a>(
     Ok(())
 }
 
-fn parse_scopes_inner<'a>(
-    word_reader: &mut WordReader,
+fn parse_scopes_inner<'a, R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
     parent_scope_idx: Option<ScopeIdx>,
     vcd: &'a mut VCD,
     signal_map: &mut HashMap<String, SignalIdx>,
@@ -328,8 +328,8 @@ fn parse_scopes_inner<'a>(
     Ok(())
 }
 
-pub(super) fn parse_scopes<'a>(
-    word_reader: &mut WordReader,
+pub(super) fn parse_scopes<'a, R: std::io::Read>(
+    word_reader: &mut WordReader<R>,
     vcd: &'a mut VCD,
     signal_map: &mut HashMap<String, SignalIdx>,
 ) -> Result<(), String> {
diff --git a/src/vcd/reader.rs b/src/vcd/reader.rs
index 9fc32ec..6ef242f 100644
--- a/src/vcd/reader.rs
+++ b/src/vcd/reader.rs
@@ -3,7 +3,6 @@
 // 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::fs::File;
 use std::io;
 use std::io::BufRead;
 use std::slice;
@@ -16,8 +15,8 @@ pub(super) struct Word(pub(super) usize);
 #[derive(Debug, Clone)]
 pub(super) struct Cursor(pub(super) Line, pub(super) Word);
 
-pub(super) struct WordReader {
-    reader: io::BufReader<File>,
+pub(super) struct WordReader<R: io::Read> {
+    reader: io::BufReader<R>,
     eof: bool,
     buffers: Vec<String>,
     curr_line: usize,
@@ -25,11 +24,11 @@ pub(super) struct WordReader {
     curr_slice: Option<(*const u8, usize, Cursor)>,
 }
 
-impl WordReader {
-    pub(super) fn new(file: File) -> WordReader {
+impl<R: std::io::Read> WordReader<R> {
+    pub(super) fn new(file: R) -> WordReader<R> {
         let reader = io::BufReader::new(file);
         WordReader {
-            reader: reader,
+            reader,
             eof: false,
             buffers: vec![],
             curr_line: 0,