[FFmpeg-devel] [PATCH 12/17] avformat/flvenc: Use array instead of linked list for index

[Andreas Rheinhardt]

Using a linked list had very much overhead (the pointer to the next
entry increased the size of the index entry struct from 16 to 24 bytes,
not to mention the overhead of having separate allocations), so it is
better to (re)allocate a continuous array for the index.
av_fast_realloc_array() is used for this purpose, in order not to
reallocate the array for each entry.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
Now no longer increasing the size of the array by a factor of two.

 libavformat/flvenc.c | 58 +++++++++++++++-----------------------------
 1 file changed, 19 insertions(+), 39 deletions(-)

diff --git a/libavformat/flvenc.c b/libavformat/flvenc.c
index 1aaf0333ca..106be3333b 100644
--- a/libavformat/flvenc.c
+++ b/libavformat/flvenc.c
@@ -74,7 +74,6 @@ typedef enum {
 typedef struct FLVFileposition {
     int64_t keyframe_position;
     double keyframe_timestamp;
-    struct FLVFileposition *next;
 } FLVFileposition;
 
 typedef struct FLVContext {
@@ -108,9 +107,9 @@ typedef struct FLVContext {
     int acurframeindex;
     int64_t keyframes_info_offset;
 
-    int64_t filepositions_count;
     FLVFileposition *filepositions;
-    FLVFileposition *head_filepositions;
+    unsigned filepositions_count;
+    unsigned filepositions_allocated;
 
     AVCodecParameters *audio_par;
     AVCodecParameters *video_par;
@@ -549,27 +548,19 @@ static void flv_write_codec_header(AVFormatContext* s, AVCodecParameters* par, i
 
 static int flv_append_keyframe_info(AVFormatContext *s, FLVContext *flv, double ts, int64_t pos)
 {
-    FLVFileposition *position = av_malloc(sizeof(FLVFileposition));
-
-    if (!position) {
-        av_log(s, AV_LOG_WARNING, "no mem for add keyframe index!\n");
+    FLVFileposition *filepos;
+
+    filepos = av_fast_realloc_array(flv->filepositions,
+                                    &flv->filepositions_allocated,
+                                    flv->filepositions_count + 1,
+                                    sizeof(*flv->filepositions));
+    if (!filepos) {
+        av_log(s, AV_LOG_WARNING, "No memory for keyframe index\n");
         return AVERROR(ENOMEM);
     }
+    flv->filepositions = filepos;
 
-    position->keyframe_timestamp = ts;
-    position->keyframe_position = pos;
-
-    if (!flv->filepositions_count) {
-        flv->filepositions = position;
-        flv->head_filepositions = flv->filepositions;
-        position->next = NULL;
-    } else {
-        flv->filepositions->next = position;
-        position->next = NULL;
-        flv->filepositions = flv->filepositions->next;
-    }
-
-    flv->filepositions_count++;
+    filepos[flv->filepositions_count++] = (FLVFileposition){ pos, ts };
 
     return 0;
 }
@@ -586,7 +577,7 @@ static int shift_data(AVFormatContext *s)
     int read_size[2];
     AVIOContext *read_pb;
 
-    metadata_size = flv->filepositions_count * 9 * 2 + 10; /* filepositions and times value */
+    metadata_size = flv->filepositions_count * 9LL * 2 + 10; /* filepositions and times value */
     metadata_size += 2 + 13; /* filepositions String */
     metadata_size += 2 + 5; /* times String */
     metadata_size += 3; /* Object end */
@@ -784,7 +775,7 @@ static int flv_write_trailer(AVFormatContext *s)
     int64_t cur_pos = avio_tell(s->pb);
 
     if (build_keyframes_idx) {
-        FLVFileposition *newflv_posinfo, *p;
+        FLVFileposition *flv_posinfo = flv->filepositions;
 
         avio_seek(pb, flv->videosize_offset, SEEK_SET);
         put_amf_double(pb, flv->videosize);
@@ -809,28 +800,17 @@ static int flv_write_trailer(AVFormatContext *s)
         avio_seek(pb, flv->keyframes_info_offset, SEEK_SET);
         put_amf_string(pb, "filepositions");
         put_amf_dword_array(pb, flv->filepositions_count);
-        for (newflv_posinfo = flv->head_filepositions; newflv_posinfo; newflv_posinfo = newflv_posinfo->next) {
-            put_amf_double(pb, newflv_posinfo->keyframe_position + flv->keyframe_index_size);
+        for (unsigned i = 0; i < flv->filepositions_count; i++) {
+            put_amf_double(pb, flv_posinfo[i].keyframe_position + flv->keyframe_index_size);
         }
 
         put_amf_string(pb, "times");
         put_amf_dword_array(pb, flv->filepositions_count);
-        for (newflv_posinfo = flv->head_filepositions; newflv_posinfo; newflv_posinfo = newflv_posinfo->next) {
-            put_amf_double(pb, newflv_posinfo->keyframe_timestamp);
+        for (unsigned i = 0; i < flv->filepositions_count; i++) {
+            put_amf_double(pb, flv_posinfo[i].keyframe_timestamp);
         }
 
-        newflv_posinfo = flv->head_filepositions;
-        while (newflv_posinfo) {
-            p = newflv_posinfo->next;
-            if (p) {
-                newflv_posinfo->next = p->next;
-                av_free(p);
-                p = NULL;
-            } else {
-                av_free(newflv_posinfo);
-                newflv_posinfo = NULL;
-            }
-        }
+        av_freep(&flv->filepositions);
 
         put_amf_string(pb, "");
         avio_w8(pb, AMF_END_OF_OBJECT);
-- 
2.20.1