Add profiling scopes

Cargo.lock

@@ -87,6 +87,25 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "profiling"
+version = "1.0.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "afbdc74edc00b6f6a218ca6a5364d6226a259d4b8ea1af4a0ea063f27e179f4d"
+dependencies = [
+ "profiling-procmacros",
+]
+
+[[package]]
+name = "profiling-procmacros"
+version = "1.0.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a65f2e60fbf1063868558d69c6beacf412dc755f9fc020f514b7955fc914fe30"
+dependencies = [
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.37"
@@ -104,6 +123,7 @@ dependencies = [
  "bytes",
  "log",
  "num-rational",
+ "profiling",
  "serde",
  "serde_json",
  "thiserror",

Cargo.toml

@@ -28,6 +28,7 @@ byteorder = "1"
 bytes = "1.1.0"
 log = "0.4.17"
 num-rational = { version = "0.4.0", features = ["serde"] }
+profiling = "1"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 thiserror = "^1.0"

src/lib.rs

@@ -5,6 +5,7 @@
 //!    * ISO/IEC 14496-14 - MP4 file format
 //!    * ISO/IEC 14496-17 - Streaming text format
 //!
+//! The top-level type you wanna look at is [`Mp4`].
 
 mod error;
 pub use error::Error;

src/mp4box/mod.rs

@@ -276,6 +276,7 @@ impl BoxHeader {
     }
 
     // TODO: if size is 0, then this box is the last one in the file
+    #[profiling::function]
     pub fn read<R: Read>(reader: &mut R) -> Result<Self> {
         // Create and read to buf.
         let mut buf = [0u8; 8]; // 8 bytes for box header.

src/reader.rs

@@ -116,6 +116,7 @@ impl Mp4 {
     /// Process each `trak` box to obtain a list of samples for each track.
     ///
     /// Note that the list will be incomplete if the file is fragmented.
+    #[profiling::function]
     fn build_tracks(&mut self) -> BTreeMap<TrackId, Track> {
         let mut tracks = BTreeMap::new();
 
@@ -272,6 +273,7 @@ impl Mp4 {
 
     /// In case the input file is fragmented, it will contain one or more `moof` boxes,
     /// which must be processed to obtain the full list of samples for each track.
+    #[profiling::function]
     fn update_sample_list(&mut self, tracks: &mut BTreeMap<TrackId, Track>) -> Result<()> {
         let mut last_run_position = 0;
 
@@ -412,17 +414,21 @@ impl Mp4 {
     /// This also updates sample offsets and the track duration if needed.
     ///
     /// After this function is called, each track's [`Track::data`] may only be indexed by one of its samples' [`Sample::offset`]s.
+    #[profiling::function]
     fn load_track_data<R: Read + Seek>(&mut self, reader: &mut R) -> Result<()> {
         for track in self.tracks.values_mut() {
+            profiling::scope!("track");
             for sample in &mut track.samples {
                 let data_offset = track.data.len();
 
+                // Allocating memory for each sample is what takes up most time in this function.
                 track
                     .data
                     .resize(track.data.len() + sample.size as usize, 0);
 
                 // at this point, `sample.offset` is the offset of the first byte of the sample in the file
                 reader.seek(SeekFrom::Start(sample.offset))?;
+
                 reader
                     .read_exact(&mut track.data[data_offset..data_offset + sample.size as usize])?;