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jpegdec: refactored gst_jpeg_dec_parse_image_data

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Fixes #579808
This commit is contained in:
Arnout Vandecappelle 2009-05-06 13:22:51 +02:00 committed by Wim Taymans
parent 788986e269
commit 99efbfcf4d
1 changed files with 27 additions and 42 deletions
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69
ext/jpeg/gstjpegdec.c
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@ -334,12 +334,6 @@ is_jpeg_start_marker (const guint8 * data)
return (data[0] == 0xff && data[1] == 0xd8);
}
static inline gboolean
is_jpeg_end_marker (const guint8 * data)
{
return (data[0] == 0xff && data[1] == 0xd9);
}
static gboolean
gst_jpeg_dec_find_jpeg_header (GstJpegDec * dec)
{
@ -445,54 +439,34 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
while (1) {
guint frame_len;
gboolean resync;
/* do we need to resync? */
if (*data != 0xff) {
resync = (*data != 0xff);
if (resync) {
GST_DEBUG ("Lost sync at 0x%08x, resyncing", data - start);
/* at the very least we expect 0xff 0xNN, thus end-1 */
while (*data != 0xff && data < end - 1)
++data;
if (is_jpeg_end_marker (data)) {
GST_DEBUG ("resynced to end marker");
goto found_eoi;
}
/* we need 0xFF 0xNN 0xLL 0xLL */
if (data >= end - 1 - 2) {
GST_DEBUG ("at end of input, without new sync, need more data");
return 0;
}
/* check if we will still be in sync if we interpret
* this as a sync point and skip this frame */
frame_len = GST_READ_UINT16_BE (data + 2);
GST_DEBUG ("possible sync at 0x%08x, frame_len=%u", data - start,
frame_len);
if (data + 2 + frame_len >= end - 1 || data[2 + frame_len] != 0xff) {
/* ignore and continue resyncing until we hit the end
* of our data or find a sync point that looks okay */
++data;
continue;
}
GST_DEBUG ("found sync at %p", data - size);
}
/* Skip over extra 0xff */
while (*data == 0xff && data < end)
++data;
/* enough bytes left for EOI marker? (we need 0xNN after the 0xff) */
/* enough bytes left for marker? (we need 0xNN after the 0xff) */
if (data >= end) {
GST_DEBUG ("at end of input and no EOI marker found, need more data");
return 0;
}
if (is_jpeg_end_marker (data - 1)) {
data--;
GST_DEBUG ("0x%08x: end marker", data - start);
goto found_eoi;
if (*data == 0xd9) {
GST_DEBUG ("0x%08x: EOI marker", data - start);
return (data - start + 1);
}
if (data + 2 >= end)
return 0;
if (*data >= 0xd0 && *data <= 0xd7)
frame_len = 0;
else if (data >= end - 2)
return 0;
else
frame_len = GST_READ_UINT16_BE (data + 1);
GST_DEBUG ("0x%08x: tag %02x, frame_len=%u", data - start - 1, *data,
@ -500,11 +474,17 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
/* the frame length includes the 2 bytes for the length; here we want at
* least 2 more bytes at the end for an end marker, thus end-2 */
if (data + 1 + frame_len >= end - 2) {
if (resync) {
GST_DEBUG ("not a valid sync (not enough data).");
/* Since *data != 0xff, the next iteration will go into resync again. */
continue;
}
/* theoretically we could have lost sync and not really need more
* data, but that's just tough luck and a broken image then */
GST_DEBUG ("at end of input and no EOI marker found, need more data");
return 0;
}
if (gst_jpeg_dec_parse_tag_has_entropy_segment (*data)) {
guint8 *d2 = data + 1 + frame_len;
guint eseglen = 0;
@ -521,14 +501,19 @@ gst_jpeg_dec_parse_image_data (GstJpegDec * dec)
GST_DEBUG ("entropy segment length=%u => frame_len=%u", eseglen,
frame_len);
}
if (resync) {
/* check if we will still be in sync if we interpret
* this as a sync point and skip this frame */
if (data[2 + frame_len] != 0xff) {
/* ignore and continue resyncing until we hit the end
* of our data or find a sync point that looks okay */
continue;
}
GST_DEBUG ("found sync at %p", data - size);
}
data += 1 + frame_len;
}
found_eoi:
/* data is assumed to point to the 0xff sync point of the
* EOI marker (so there is one more byte after that) */
g_assert (is_jpeg_end_marker (data));
return ((data + 1) - start + 1);
}
/* shamelessly ripped from jpegutils.c in mjpegtools */