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jpegparse: improve buffer scanning

Browse source 
Specifically, when scanning for entropy data segment length and needing
more data, do not rescan from start next time around, but resume at
last position.

See also #583047.
This commit is contained in:
Mark Nauwelaerts 2010-04-29 16:33:44 +02:00
parent 01c5a78f0b
commit d68a4c1dcc
1 changed files with 15 additions and 3 deletions
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18
gst/jpegformat/gstjpegparse.c
View file

@ -78,6 +78,7 @@ struct _GstJpegParsePrivate
GstAdapter *adapter;
guint last_offset;
guint last_entropy_len;
/* negotiated state */
gint caps_width, caps_height;
@ -291,7 +292,8 @@ gst_jpeg_parse_parse_tag_has_entropy_segment (guint8 tag)
* enough data.
*/
static guint
gst_jpeg_parse_match_next_marker (const guint8 * data, guint size)
gst_jpeg_parse_match_next_marker (GstJpegParse * parse, const guint8 * data,
guint size)
{
guint marker_len;
guint8 tag;
@ -316,11 +318,19 @@ gst_jpeg_parse_match_next_marker (const guint8 * data, guint size)
goto need_more_data;
if (G_UNLIKELY (gst_jpeg_parse_parse_tag_has_entropy_segment (tag))) {
if (parse->priv->last_entropy_len) {
marker_len = parse->priv->last_entropy_len;
GST_LOG_OBJECT (parse, "resuming entropy segment scan at len %u",
marker_len);
}
while (!(data[marker_len] == 0xff && data[marker_len + 1] != 0x00)) {
++marker_len;
if (G_UNLIKELY (marker_len + 2 > size))
if (G_UNLIKELY (marker_len + 2 > size)) {
parse->priv->last_entropy_len = marker_len;
goto need_more_data;
}
}
parse->priv->last_entropy_len = 0;
}
return marker_len;
@ -369,7 +379,7 @@ gst_jpeg_parse_find_end_marker (GstJpegParse * parse, const guint8 * data,
return offset;
}
/* Skip over this marker. */
marker_len = gst_jpeg_parse_match_next_marker (data + offset,
marker_len = gst_jpeg_parse_match_next_marker (parse, data + offset,
size - offset);
if (G_UNLIKELY (marker_len == -1)) {
return -1;
@ -736,6 +746,7 @@ gst_jpeg_parse_push_buffer (GstJpegParse * parse, guint len)
/* reset the offset (only when we flushed) */
parse->priv->last_offset = 2;
parse->priv->last_entropy_len = 0;
outbuf = gst_adapter_take_buffer (parse->priv->adapter, len);
if (outbuf == NULL) {
@ -885,6 +896,7 @@ gst_jpeg_parse_change_state (GstElement * element, GstStateChange transition)
parse->priv->next_ts = GST_CLOCK_TIME_NONE;
parse->priv->last_offset = 2;
parse->priv->last_entropy_len = 0;
default:
break;
}