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adapter: fix _masked_scan_uint32() at boundaries

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gst_adapter_masked_scan_uint32 could return values smaller than offset
if the first byte(s) of the mask are 0 and the pattern matches the
beginning of the adapter.
Added examples to documentation of gst_adapter_masked_scan_uint32().
Also added some more masked boundary tests.
Fixes #584118
This commit is contained in:
Arnout Vandecappelle 2009-05-28 22:02:21 +02:00 committed by Wim Taymans
parent 8f7c59936e
commit c74c3bf1b3
2 changed files with 46 additions and 4 deletions
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37
libs/gst/base/gstadapter.c
View file

@ -740,13 +740,37 @@ gst_adapter_prev_timestamp (GstAdapter * adapter, guint64 * distance)
* @size: number of bytes to scan from offset
*
* Scan for pattern @pattern with applied mask @mask in the adapter data,
* starting from offset @offset.
* starting from offset @offset.
*
* The bytes in @pattern and @mask are interpreted left-to-right, regardless
* of endianness. All four bytes of the pattern must be present in the
* adapter for it to match, even if the first or last bytes are masked out.
*
* It is an error to call this function without making sure that there is
* enough data (offset+size bytes) in the adapter.
*
* Returns: offset of the first match, or -1 if no match was found.
*
* Example:
* <programlisting>
* // Assume the adapter contains 0x00 0x01 0x02 ... 0xfe 0xff
*
* gst_adapter_masked_scan_uint32 (adapter, 0x00010203, 0xffffffff, 0, 256);
* // -> returns 0
* gst_adapter_masked_scan_uint32 (adapter, 0x00010203, 0xffffffff, 1, 255);
* // -> returns -1
* gst_adapter_masked_scan_uint32 (adapter, 0x01020304, 0xffffffff, 1, 255);
* // -> returns 1
* gst_adapter_masked_scan_uint32 (adapter, 0x0001, 0xffff, 0, 256);
* // -> returns -1
* gst_adapter_masked_scan_uint32 (adapter, 0x0203, 0xffff, 0, 256);
* // -> returns 0
* gst_adapter_masked_scan_uint32 (adapter, 0x02030000, 0xffff0000, 0, 256);
* // -> returns 2
* gst_adapter_masked_scan_uint32 (adapter, 0x02030000, 0xffff0000, 0, 4);
* // -> returns -1
* </programlisting>
*
* Since: 0.10.24
*/
guint
@ -781,6 +805,7 @@ gst_adapter_masked_scan_uint32 (GstAdapter * adapter, guint32 mask,
/* get the data now */
bsize -= skip;
bdata = GST_BUFFER_DATA (buf) + skip;
skip = 0;
/* set the state to something that does not match */
state = ~pattern;
@ -790,15 +815,19 @@ gst_adapter_masked_scan_uint32 (GstAdapter * adapter, guint32 mask,
bsize = MIN (bsize, size);
for (i = 0; i < bsize; i++) {
state = ((state << 8) | bdata[i]);
if (G_UNLIKELY ((state & mask) == pattern))
return offset + i - 3;
if (G_UNLIKELY ((state & mask) == pattern)) {
/* we have a match but we need to have skipped at
* least 4 bytes to fill the state. */
if (G_LIKELY (skip + i >= 3))
return offset + skip + i - 3;
}
}
size -= bsize;
if (size == 0)
break;
/* nothing found yet, go to next buffer */
offset += bsize;
skip += bsize;
g = g_slist_next (g);
buf = g->data;
bsize = GST_BUFFER_SIZE (buf);

13
tests/check/libs/adapter.c
View file

@ -547,6 +547,19 @@ GST_START_TEST (test_scan)
gst_adapter_masked_scan_uint32 (adapter, 0x00ffffff, 0x00656667, 0x64,
100);
fail_unless (offset == 0x64);
offset =
gst_adapter_masked_scan_uint32 (adapter, 0x000000ff, 0x00000000, 0, 100);
fail_unless (offset == -1);
offset =
gst_adapter_masked_scan_uint32 (adapter, 0x000000ff, 0x00000003, 0, 100);
fail_unless (offset == 0);
offset =
gst_adapter_masked_scan_uint32 (adapter, 0x000000ff, 0x00000061, 0x61,
100);
fail_unless (offset == -1);
offset =
gst_adapter_masked_scan_uint32 (adapter, 0xff000000, 0x61000000, 0, 0x62);
fail_unless (offset == -1);
/* does not even exist */
offset =
gst_adapter_masked_scan_uint32 (adapter, 0x00ffffff, 0xffffffff, 0x65,