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bytereader: add gst_byte_reader_masked_scan_uint32()
Add a pattern scan function similar to the one recently added to GstAdapter, and a unit test (based on the adapter one). Fixes #585592. API: add gst_byte_reader_masked_scan_uint32()
This commit is contained in:
Tim-Philipp Müller
parent
c403e4b7f0
commit
674447fafe
5 changed files with 179 additions and 0 deletions
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@ -446,6 +446,8 @@ gst_byte_reader_peek_float64_be
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gst_byte_reader_get_data
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gst_byte_reader_peek_data
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gst_byte_reader_masked_scan_uint32
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</SECTION>
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<SECTION>
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@ -1207,3 +1207,81 @@ gst_byte_reader_peek_data (GstByteReader * reader, guint size,
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*val = reader->data + reader->byte;
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return TRUE;
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}
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/**
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* gst_byte_reader_masked_scan_uint32:
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* @reader: a #GstByteReader
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* @mask: mask to apply to data before matching against @pattern
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* @pattern: pattern to match (after mask is applied)
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* @offset: offset into the adapter data from which to start scanning
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* @size: number of bytes to scan from offset
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*
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* Scan for pattern @pattern with applied mask @mask in the adapter data,
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* starting from offset @offset.
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*
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* The bytes in @pattern and @mask are interpreted left-to-right, regardless
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* of endianness. All four bytes of the pattern must be present in the
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* adapter for it to match, even if the first or last bytes are masked out.
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*
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* It is an error to call this function without making sure that there is
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* enough data (offset+size bytes) in the byte reader.
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*
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* Returns: offset of the first match, or -1 if no match was found.
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*
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* Example:
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* <programlisting>
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* // Assume the reader contains 0x00 0x01 0x02 ... 0xfe 0xff
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*
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* gst_byte_reader_masked_scan_uint32 (reader, 0x00010203, 0xffffffff, 0, 256);
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* // -> returns 0
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* gst_byte_reader_masked_scan_uint32 (reader, 0x00010203, 0xffffffff, 1, 255);
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* // -> returns -1
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* gst_byte_reader_masked_scan_uint32 (reader, 0x01020304, 0xffffffff, 1, 255);
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* // -> returns 1
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* gst_byte_reader_masked_scan_uint32 (reader, 0x0001, 0xffff, 0, 256);
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* // -> returns -1
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* gst_byte_reader_masked_scan_uint32 (reader, 0x0203, 0xffff, 0, 256);
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* // -> returns 0
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* gst_byte_reader_masked_scan_uint32 (reader, 0x02030000, 0xffff0000, 0, 256);
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* // -> returns 2
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* gst_byte_reader_masked_scan_uint32 (reader, 0x02030000, 0xffff0000, 0, 4);
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* // -> returns -1
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* </programlisting>
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*
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* Since: 0.10.24
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*/
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guint
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gst_byte_reader_masked_scan_uint32 (GstByteReader * reader, guint32 mask,
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guint32 pattern, guint offset, guint size)
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{
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const guint8 *data;
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guint32 state;
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guint i;
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g_return_val_if_fail (size > 0, -1);
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g_return_val_if_fail (offset + size <= reader->size, -1);
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/* we can't find the pattern with less than 4 bytes */
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if (G_UNLIKELY (size < 4))
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return -1;
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data = reader->data + reader->byte + offset;
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/* set the state to something that does not match */
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state = ~pattern;
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/* now find data */
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for (i = 0; i < size; i++) {
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/* throw away one byte and move in the next byte */
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state = ((state << 8) | data[i]);
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if (G_UNLIKELY ((state & mask) == pattern)) {
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/* we have a match but we need to have skipped at
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* least 4 bytes to fill the state. */
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if (G_LIKELY (i >= 3))
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return offset + i - 3;
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}
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}
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/* nothing found */
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return -1;
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}
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@ -105,6 +105,12 @@ gboolean gst_byte_reader_peek_float64_be (GstByteReader *reader, gdouble *val);
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gboolean gst_byte_reader_get_data (GstByteReader *reader, guint size, const guint8 **val);
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gboolean gst_byte_reader_peek_data (GstByteReader *reader, guint size, const guint8 **val);
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guint gst_byte_reader_masked_scan_uint32 (GstByteReader * reader,
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guint32 mask,
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guint32 pattern,
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guint offset,
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guint size);
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/**
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* GST_BYTE_READER_INIT:
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* @data: Data from which the #GstByteReader should read
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@ -460,6 +460,97 @@ GST_START_TEST (test_position_tracking)
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GST_END_TEST;
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#define do_scan(r,m,p,o,s,x) \
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fail_unless_equals_int (gst_byte_reader_masked_scan_uint32 (r,m,p,o,s), x);
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GST_START_TEST (test_scan)
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{
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GstByteReader reader;
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guint8 data[200];
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guint i;
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/* fill half the buffer with a pattern */
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for (i = 0; i < 100; i++)
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data[i] = i;
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gst_byte_reader_init (&reader, data, 100);
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/* find first bytes */
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do_scan (&reader, 0xffffffff, 0x00010203, 0, 100, 0);
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do_scan (&reader, 0xffffffff, 0x01020304, 0, 100, 1);
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do_scan (&reader, 0xffffffff, 0x01020304, 1, 99, 1);
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/* offset is past the pattern start */
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do_scan (&reader, 0xffffffff, 0x01020304, 2, 98, -1);
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/* not enough bytes to find the pattern */
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do_scan (&reader, 0xffffffff, 0x02030405, 2, 3, -1);
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do_scan (&reader, 0xffffffff, 0x02030405, 2, 4, 2);
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/* size does not include the last scanned byte */
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do_scan (&reader, 0xffffffff, 0x40414243, 0, 0x41, -1);
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do_scan (&reader, 0xffffffff, 0x40414243, 0, 0x43, -1);
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do_scan (&reader, 0xffffffff, 0x40414243, 0, 0x44, 0x40);
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/* past the start */
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do_scan (&reader, 0xffffffff, 0x40414243, 65, 10, -1);
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do_scan (&reader, 0xffffffff, 0x40414243, 64, 5, 64);
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do_scan (&reader, 0xffffffff, 0x60616263, 65, 35, 0x60);
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do_scan (&reader, 0xffffffff, 0x60616263, 0x60, 4, 0x60);
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/* past the start */
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do_scan (&reader, 0xffffffff, 0x60616263, 0x61, 3, -1);
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do_scan (&reader, 0xffffffff, 0x60616263, 99, 1, -1);
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/* add more data to the buffer */
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for (i = 100; i < 200; i++)
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data[i] = i;
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gst_byte_reader_init (&reader, data, 200);
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/* past the start */
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do_scan (&reader, 0xffffffff, 0x60616263, 0x61, 6, -1);
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/* this should work */
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do_scan (&reader, 0xffffffff, 0x61626364, 0x61, 4, 0x61);
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/* not enough data */
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do_scan (&reader, 0xffffffff, 0x62636465, 0x61, 4, -1);
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do_scan (&reader, 0xffffffff, 0x62636465, 0x61, 5, 0x62);
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do_scan (&reader, 0xffffffff, 0x62636465, 0, 120, 0x62);
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/* border conditions */
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do_scan (&reader, 0xffffffff, 0x62636465, 0, 200, 0x62);
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do_scan (&reader, 0xffffffff, 0x63646566, 0, 200, 0x63);
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/* we completely searched the first list */
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do_scan (&reader, 0xffffffff, 0x64656667, 0, 200, 0x64);
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/* skip first buffer */
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do_scan (&reader, 0xffffffff, 0x64656667, 0x64, 100, 0x64);
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/* past the start */
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do_scan (&reader, 0xffffffff, 0x64656667, 0x65, 10, -1);
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/* not enough data to scan */
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do_scan (&reader, 0xffffffff, 0x64656667, 0x63, 4, -1);
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do_scan (&reader, 0xffffffff, 0x64656667, 0x63, 5, 0x64);
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 0, 199, -1);
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 0x62, 102, 0xc4);
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/* different masks */
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do_scan (&reader, 0x00ffffff, 0x00656667, 0x64, 100, 0x64);
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do_scan (&reader, 0x000000ff, 0x00000000, 0, 100, -1);
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do_scan (&reader, 0x000000ff, 0x00000003, 0, 100, 0);
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do_scan (&reader, 0x000000ff, 0x00000061, 0x61, 100, -1);
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do_scan (&reader, 0xff000000, 0x61000000, 0, 0x62, -1);
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/* does not even exist */
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do_scan (&reader, 0x00ffffff, 0xffffffff, 0x65, 99, -1);
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/* flush some bytes */
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gst_byte_reader_skip (&reader, 0x20);
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do_scan (&reader, 0xffffffff, 0x20212223, 0, 100, 0);
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do_scan (&reader, 0xffffffff, 0x20212223, 0, 4, 0);
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 0x62, 70, 0xa4);
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 0, 168, 0xa4);
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 164, 4, 0xa4);
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 0x44, 100, 0xa4);
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/* not enough bytes */
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do_scan (&reader, 0xffffffff, 0xc4c5c6c7, 0x44, 99, -1);
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}
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GST_END_TEST;
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static Suite *
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gst_byte_reader_suite (void)
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{
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@ -476,6 +567,7 @@ gst_byte_reader_suite (void)
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tcase_add_test (tc_chain, test_get_float_le);
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tcase_add_test (tc_chain, test_get_float_be);
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tcase_add_test (tc_chain, test_position_tracking);
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tcase_add_test (tc_chain, test_scan);
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return s;
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}
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@ -101,6 +101,7 @@ EXPORTS
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gst_byte_reader_get_uint8
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gst_byte_reader_init
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gst_byte_reader_init_from_buffer
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gst_byte_reader_masked_scan_uint32
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gst_byte_reader_new
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gst_byte_reader_new_from_buffer
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gst_byte_reader_peek_data
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