diff mbox series

[FFmpeg-devel] lavf/mxfdec: Set a scan direction explicitly

Message ID 6581ee5fba8e34ab080387a600b179f1144841d3.camel@haerdin.se
State New
Headers show
Series [FFmpeg-devel] lavf/mxfdec: Set a scan direction explicitly | expand

Checks

Context Check Description
yinshiyou/commit_msg_loongarch64 warning Please wrap lines in the body of the commit message between 60 and 72 characters.

Commit Message

Tomas Härdin Oct. 14, 2024, 2:46 p.m. UTC 
Passes fate-mxf

/Tomas
diff mbox series

Patch

From 6e47a432512444426c88484f99d18c6b052bb1f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= <git@haerdin.se>
Date: Mon, 14 Oct 2024 16:45:35 +0200
Subject: [PATCH] lavf/mxfdec: Set a scan direction explicitly

This prevents a theoretical case where seeks to a gap in an index can cause an infinite loop
---
 libavformat/mxfdec.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index e5f59089ab..27e8e0c261 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -1907,7 +1907,7 @@  static int64_t mxf_essence_container_end(MXFContext *mxf, int body_sid)
 /* EditUnit -> absolute offset */
 static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_table, int64_t edit_unit, AVRational edit_rate, int64_t *edit_unit_out, int64_t *offset_out, MXFPartition **partition_out, int nag)
 {
-    int i = 0;
+    int i = 0, dir = 0;
     int64_t index_duration, index_end;
     MXFIndexTableSegment *first_segment, *last_segment;
 
@@ -1939,7 +1939,7 @@  static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_t
         i = FFMAX(0, FFMIN(index_table->nb_segments - 1, i64));
     }
 
-    for (; i >= 0 && i < index_table->nb_segments;) {
+    for (; i >= 0 && i < index_table->nb_segments; i += dir) {
         MXFIndexTableSegment *s = index_table->segments[i];
 
         if (s->index_start_position <= edit_unit && edit_unit < s->index_start_position + s->index_duration) {
@@ -1969,12 +1969,14 @@  static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_t
                 *edit_unit_out = av_rescale_q(edit_unit, edit_rate, s->index_edit_rate);
 
             return mxf_absolute_bodysid_offset(mxf, index_table->body_sid, offset_temp, offset_out, partition_out);
-        } else if (edit_unit < s->index_start_position) {
-            // the segments are sorted by IndexStartPosition, so this is guaranteed to terminate
-            i--;
-        } else {
-            // edit_unit >= s->index_start_position + s->index_duration
-            i++;
+        } else if (dir == 0) {
+            // scan backwards if the segment is earlier than the current IndexStartPosition
+            // else scan forwards
+            if (edit_unit < s->index_start_position) {
+                dir = -1;
+            } else {
+                dir = 1;
+            }
         }
     }
 
-- 
2.39.2