fix panic when seeking into holes

1 files changed, 24 insertions, 8 deletions

diff --git a/remuxer/src/remux.rs b/remuxer/src/remux.rs
index df4f67d..0e7877d 100644
--- a/remuxer/src/remux.rs
+++ b/remuxer/src/remux.rs
@@ -28,6 +28,13 @@ use std::{
     time::Instant,
 };
 
+struct ClusterLayout {
+    position: usize,
+    timestamp: u64,
+    source_offsets: Vec<Option<usize>>,
+    blocks: Vec<(usize, BlockIndex)>,
+}
+
 pub fn remux_stream_into(
     writer: impl Write,
     range: Range<usize>,
@@ -113,13 +120,6 @@ pub fn remux_stream_into(
         .collect();
     output.write_tag(&MatroskaTag::Tracks(Master::Collected(tracks_header)))?;
 
-    struct ClusterLayout {
-        position: usize,
-        timestamp: u64,
-        source_offsets: Vec<Option<usize>>,
-        blocks: Vec<(usize, BlockIndex)>,
-    }
-
     let mut segment_layout: Vec<ClusterLayout> = {
         let mut cluster_pts = 0;
         let mut clusters = vec![];
@@ -273,7 +273,10 @@ pub fn remux_stream_into(
         .map(|(i, inp)| {
             inp.reader
                 .seek(
-                    segment_layout[skip].source_offsets[i].unwrap(), // TODO will crash if there is a "hole"
+                    // the seek target might be a hole; we continue until the next clust of that track.
+                    // this should be fine since tracks are only read according to segment_layout
+                    find_first_cluster_with_off(&segment_layout, skip, i)
+                        .ok_or(anyhow!("cluster hole at eof"))?,
                     MatroskaTag::Cluster(Master::Start),
                 )
                 .context("seeking in input")?;
@@ -325,3 +328,16 @@ pub fn remux_stream_into(
     output.write_tag(&MatroskaTag::Segment(Master::End))?;
     Ok(())
 }
+
+fn find_first_cluster_with_off(
+    segment_layout: &[ClusterLayout],
+    skip: usize,
+    track: usize,
+) -> Option<usize> {
+    for skip in skip..segment_layout.len() {
+        if let Some(off) = segment_layout[skip].source_offsets[track] {
+            return Some(off);
+        }
+    }
+    None
+}