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gst/typefind/gsttypefindfunctions.c: Refactor a bit: use context structure to track parsing offset and size of availa...

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Original commit message from CVS:
* gst/typefind/gsttypefindfunctions.c: (MpegVideoStreamCtx),
(mpeg_video_stream_ctx_advance), (mpeg_video_stream_ctx_ensure_data),
(mpeg_video_stream_type_find):
Refactor a bit: use context structure to track parsing offset and size of
available data and make the code a bit clearer. Fixes bad memory access
in #356937.
This commit is contained in:
Tim-Philipp Müller 2008-04-30 14:37:52 +00:00
parent 802c45b10b
commit 5f6db60a4d
2 changed files with 81 additions and 51 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2008-04-30 Tim-Philipp Müller <tim.muller at collabora co uk>
* gst/typefind/gsttypefindfunctions.c: (MpegVideoStreamCtx),
(mpeg_video_stream_ctx_advance), (mpeg_video_stream_ctx_ensure_data),
(mpeg_video_stream_type_find):
Refactor a bit: use context structure to track parsing offset and size of
available data and make the code a bit clearer. Fixes bad memory access
in #356937.
2008-04-28 Michael Smith <msmith@songbirdnest.com>
* gst/playback/test4.c:

123
gst/typefind/gsttypefindfunctions.c
View file

@ -1667,12 +1667,47 @@ mpeg_video_type_find (GstTypeFind * tf, gpointer unused)
#define GST_MPEGVID_TYPEFIND_TRY_SYNC (100 * 1024) /* 100 kB */
#define GST_MPEGVID_TYPEFIND_SYNC_SIZE 2048
typedef struct
{
guint64 offset;
guint8 *data;
gint size;
} MpegVideoStreamCtx;
static inline void
mpeg_video_stream_ctx_advance (GstTypeFind * tf, MpegVideoStreamCtx * c,
guint bytes_to_skip)
{
c->offset += bytes_to_skip;
if (c->size > bytes_to_skip) {
c->size -= bytes_to_skip;
c->data += bytes_to_skip;
} else {
c->data += c->size;
c->size = 0;
}
}
static inline gboolean
mpeg_video_stream_ctx_ensure_data (GstTypeFind * tf, MpegVideoStreamCtx * c,
gint min_len)
{
if (c->size >= min_len)
return TRUE;
c->data = gst_type_find_peek (tf, c->offset, GST_MPEGVID_TYPEFIND_SYNC_SIZE);
if (c->data == NULL)
return FALSE;
c->size = GST_MPEGVID_TYPEFIND_SYNC_SIZE;
return TRUE;
}
static void
mpeg_video_stream_type_find (GstTypeFind * tf, gpointer unused)
{
gint size = 0, found = 0;
guint64 skipped = 0;
guint8 *data = NULL;
MpegVideoStreamCtx c = { 0, NULL, 0 };
gint found = 0;
while (1) {
if (found >= GST_MPEGVID_TYPEFIND_TRY_PICTURES) {
@ -1685,65 +1720,51 @@ mpeg_video_stream_type_find (GstTypeFind * tf, gpointer unused)
return;
}
if (skipped > GST_MPEGVID_TYPEFIND_TRY_SYNC)
if (c.offset >= GST_MPEGVID_TYPEFIND_TRY_SYNC)
break;
if (size < 5) {
data = gst_type_find_peek (tf, skipped, GST_MPEGVID_TYPEFIND_SYNC_SIZE);
if (!data)
break;
size = GST_MPEGVID_TYPEFIND_SYNC_SIZE;
}
if (!mpeg_video_stream_ctx_ensure_data (tf, &c, 5))
break;
if (IS_MPEG_HEADER (data)) {
if (IS_MPEG_HEADER (c.data)) {
/* An MPEG PACK header indicates that this isn't an elementary stream */
if (IS_MPEG_PACK_CODE (data[3])) {
if (mpeg_sys_is_valid_pack (tf, data, size, NULL))
if (IS_MPEG_PACK_CODE (c.data[3])) {
if (mpeg_sys_is_valid_pack (tf, c.data, c.size, NULL))
break;
}
/* are we a sequence (0xB3) or GOP (0xB8) header? */
if (data[3] == 0xB3 || data[3] == 0xB8) {
size -= 8;
data += 8;
skipped += 8;
if (data[3] == 0xB3)
continue;
else if (size < 4) {
data =
gst_type_find_peek (tf, skipped, GST_MPEGVID_TYPEFIND_SYNC_SIZE);
size = GST_MPEGVID_TYPEFIND_SYNC_SIZE;
if (!data)
break;
}
/* else, we should now see an image */
}
}
/* image header (and, when found, slice header) */
if (IS_MPEG_HEADER (data) && data[4] == 0x0) {
size -= 8;
data += 8;
skipped += 8;
if (size < 5) {
data = gst_type_find_peek (tf, skipped, GST_MPEGVID_TYPEFIND_SYNC_SIZE);
size = GST_MPEGVID_TYPEFIND_SYNC_SIZE;
if (!data)
break;
}
if ((IS_MPEG_HEADER (data) && data[3] == 0x1) ||
(IS_MPEG_HEADER (data + 1) && data[4] == 0x1)) {
size -= 4;
data += 4;
skipped += 4;
found += 1;
/* are we a sequence (0xB3) header? */
if (c.data[3] == 0xB3) {
mpeg_video_stream_ctx_advance (tf, &c, 4 + 8);
continue;
}
/* ... or a GOP (0xB8) header? */
if (c.data[3] == 0xB8) {
mpeg_video_stream_ctx_advance (tf, &c, 8);
continue;
}
/* ... else, we should now see an image header ... */
/* is [4] really what we want here, not [3]? Won't [4] == 0 only work for
* the first image or the first few images? (tpm) */
if (c.data[4] == 0x00) {
mpeg_video_stream_ctx_advance (tf, &c, 8);
if (!mpeg_video_stream_ctx_ensure_data (tf, &c, 5))
break;
/* .. followed by a slice header */
if ((IS_MPEG_HEADER (c.data + 0) && c.data[3] == 0x01) ||
(IS_MPEG_HEADER (c.data + 1) && c.data[4] == 0x01)) {
mpeg_video_stream_ctx_advance (tf, &c, 4);
found += 1;
continue;
}
}
}
size--;
data++;
skipped++;
mpeg_video_stream_ctx_advance (tf, &c, 1);
}
}