static inline uint32_t
_masked_scan_uint32_peek (const ByteReader * reader,
uint32_t mask, uint32_t pattern, uint32_t offset, uint32_t size, uint32_t * value)
{
const uint8_t *data;
uint32_t state;
uint32_t i;
g_return_val_if_fail (size > 0, -1);
g_return_val_if_fail ((uint64_t) offset + size <= reader->size - reader->byte,
-1);
/* we can't find the pattern with less than 4 bytes */
if (G_UNLIKELY (size < 4))
return -1;
data = reader->data + reader->byte + offset;
/* Handle special case found in MPEG and H264 */
if ((pattern == 0x00000100) && (mask == 0xffffff00)) {
uint32_t ret = _scan_for_start_code (data, offset, size);
if (G_UNLIKELY (value))
*value = (1 << 8) | data[ret + 3];
return ret;
}
/* set the state to something that does not match */
state = ~pattern;
/* now find data */
for (i = 0; i < size; i++) {
/* throw away one byte and move in the next byte */
state = ((state << 8) | data[i]);
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 (i >= 3)) {
if (value)
*value = state;
return offset + i - 3;
}
}
}
/* nothing found */
return -1;
}
/**
* gst_byte_reader_masked_scan_uint32:
* @reader: a #GstByteReader
* @mask: mask to apply to data before matching against @pattern
* @pattern: pattern to match (after mask is applied)
* @offset: offset from which to start scanning, relative to the current
* position
* @size: number of bytes to scan from offset
*
* Scan for pattern @pattern with applied mask @mask in the byte reader data,
* starting from offset @offset relative to the current position.
*
* 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
* byte reader data 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 byte reader.
*
* Returns: offset of the first match, or -1 if no match was found.
*
* Example:
* <programlisting>
* // Assume the reader contains 0x00 0x01 0x02 ... 0xfe 0xff
*
* gst_byte_reader_masked_scan_uint32 (reader, 0xffffffff, 0x00010203, 0, 256);
* // -> returns 0
* gst_byte_reader_masked_scan_uint32 (reader, 0xffffffff, 0x00010203, 1, 255);
* // -> returns -1
* gst_byte_reader_masked_scan_uint32 (reader, 0xffffffff, 0x01020304, 1, 255);
* // -> returns 1
* gst_byte_reader_masked_scan_uint32 (reader, 0xffff, 0x0001, 0, 256);
* // -> returns -1
* gst_byte_reader_masked_scan_uint32 (reader, 0xffff, 0x0203, 0, 256);
* // -> returns 0
* gst_byte_reader_masked_scan_uint32 (reader, 0xffff0000, 0x02030000, 0, 256);
* // -> returns 2
* gst_byte_reader_masked_scan_uint32 (reader, 0xffff0000, 0x02030000, 0, 4);
* // -> returns -1
* </programlisting>
*/
guint
gst_byte_reader_masked_scan_uint32 (const GstByteReader * reader, guint32 mask,
guint32 pattern, guint offset, guint size)
{
const guint8 *data;
guint32 state;
guint i;
g_return_val_if_fail (size > 0, -1);
g_return_val_if_fail ((guint64) offset + size <= reader->size - reader->byte,
-1);
/* we can't find the pattern with less than 4 bytes */
if (G_UNLIKELY (size < 4))
return -1;
data = reader->data + reader->byte + offset;
/* Handle special case found in MPEG and H264 */
if ((pattern == 0x00000100) && (mask == 0xffffff00))
return _scan_for_start_code (data, offset, size);
/* set the state to something that does not match */
state = ~pattern;
/* now find data */
for (i = 0; i < size; i++) {
/* throw away one byte and move in the next byte */
state = ((state << 8) | data[i]);
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 (i >= 3))
return offset + i - 3;
}
}
/* nothing found */
return -1;
}
