[FFmpeg-cvslog] avformat/matroskadec: use av_fast_realloc to reallocate ebml list arrays

[James Almer]

ffmpeg | branch: master | James Almer <jamrial at gmail.com> | Tue Sep  3 18:45:04 2019 -0300| [3b3150c45f1ebb3635e55e76b63439d8d62de85f] | committer: James Almer

avformat/matroskadec: use av_fast_realloc to reallocate ebml list arrays

Speeds up the process considerably.

Fixes ticket #8109.

Suggested-by: nevcairiel
Suggested-by: cehoyos
Signed-off-by: James Almer <jamrial at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=3b3150c45f1ebb3635e55e76b63439d8d62de85f
---

 libavformat/matroskadec.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 439ee462a5..8c4ff30935 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -110,6 +110,7 @@ typedef const struct EbmlSyntax {
 
 typedef struct EbmlList {
     int nb_elem;
+    unsigned int alloc_elem_size;
     void *elem;
 } EbmlList;
 
@@ -1236,8 +1237,13 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
         data = (char *) data + syntax->data_offset;
         if (syntax->list_elem_size) {
             EbmlList *list = data;
-            void *newelem = av_realloc_array(list->elem, list->nb_elem + 1,
-                                                   syntax->list_elem_size);
+            void *newelem;
+
+            if ((unsigned)list->nb_elem + 1 >= UINT_MAX / syntax->list_elem_size)
+                return AVERROR(ENOMEM);
+            newelem = av_fast_realloc(list->elem,
+                                      &list->alloc_elem_size,
+                                      (list->nb_elem + 1) * syntax->list_elem_size);
             if (!newelem)
                 return AVERROR(ENOMEM);
             list->elem = newelem;
@@ -1490,6 +1496,7 @@ static void ebml_free(EbmlSyntax *syntax, void *data)
                     ebml_free(syntax[i].def.n, ptr);
                 av_freep(&list->elem);
                 list->nb_elem = 0;
+                list->alloc_elem_size = 0;
             } else
                 ebml_free(syntax[i].def.n, data_off);
         default: