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https://github.com/mpv-player/mpv
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faster (and simpler) bitstream reader (in C)
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@3571 b3059339-0415-0410-9bf9-f77b7e298cf2
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@ -31,7 +31,12 @@
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#define BUFFER_SIZE 4096
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#define BUFFER_SIZE 4096
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#ifdef ALT_BITSTREAM_READER
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int indx=0;
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uint32_t * buffer_start;
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#else
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static uint32_t * buffer_start;
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static uint32_t * buffer_start;
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#endif
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uint32_t bits_left;
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uint32_t bits_left;
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uint32_t current_word;
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uint32_t current_word;
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@ -43,6 +48,9 @@ void bitstream_set_ptr (uint8_t * buf)
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align = (int)buf & 3;
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align = (int)buf & 3;
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buffer_start = (uint32_t *) (buf - align);
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buffer_start = (uint32_t *) (buf - align);
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bits_left = 0;
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bits_left = 0;
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#ifdef ALT_BITSTREAM_READER
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indx=0;
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#endif
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bitstream_get (align * 8);
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bitstream_get (align * 8);
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}
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}
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@ -21,6 +21,9 @@
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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*/
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// alternative (faster) bitstram reader (reades upto 3 bytes over the end of the input)
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#define ALT_BITSTREAM_READER
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/* (stolen from the kernel) */
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/* (stolen from the kernel) */
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#ifdef WORDS_BIGENDIAN
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#ifdef WORDS_BIGENDIAN
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@ -46,18 +49,33 @@
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# endif
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# endif
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#endif
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#endif
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#ifdef ALT_BITSTREAM_READER
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extern uint32_t *buffer_start;
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extern int indx;
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#else
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extern uint32_t bits_left;
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extern uint32_t bits_left;
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extern uint32_t current_word;
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extern uint32_t current_word;
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#endif
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void bitstream_set_ptr (uint8_t * buf);
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void bitstream_set_ptr (uint8_t * buf);
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uint32_t bitstream_get_bh(uint32_t num_bits);
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uint32_t bitstream_get_bh(uint32_t num_bits);
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int32_t bitstream_get_bh_2(uint32_t num_bits);
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int32_t bitstream_get_bh_2(uint32_t num_bits);
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static inline uint32_t
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static inline uint32_t
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bitstream_get(uint32_t num_bits)
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bitstream_get(uint32_t num_bits) // note num_bits is practically a constant due to inlineing
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{
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{
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#ifdef ALT_BITSTREAM_READER
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uint32_t result= swab32( *(uint32_t *)(((uint8_t *)buffer_start)+(indx>>3)) );
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result<<= (indx&0x07);
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result>>= 32 - num_bits;
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indx+= num_bits;
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return result;
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#else
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uint32_t result;
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uint32_t result;
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if(num_bits < bits_left) {
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if(num_bits < bits_left) {
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result = (current_word << (32 - bits_left)) >> (32 - num_bits);
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result = (current_word << (32 - bits_left)) >> (32 - num_bits);
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bits_left -= num_bits;
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bits_left -= num_bits;
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@ -65,11 +83,21 @@ bitstream_get(uint32_t num_bits)
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}
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}
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return bitstream_get_bh(num_bits);
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return bitstream_get_bh(num_bits);
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#endif
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}
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}
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static inline int32_t
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static inline int32_t
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bitstream_get_2(uint32_t num_bits)
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bitstream_get_2(uint32_t num_bits)
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{
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{
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#ifdef ALT_BITSTREAM_READER
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int32_t result= swab32( *(uint32_t *)(((uint8_t *)buffer_start)+(indx>>3)) );
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result<<= (indx&0x07);
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result>>= 32 - num_bits;
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indx+= num_bits;
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return result;
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#else
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int32_t result;
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int32_t result;
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if(num_bits < bits_left) {
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if(num_bits < bits_left) {
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@ -79,4 +107,5 @@ bitstream_get_2(uint32_t num_bits)
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}
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}
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return bitstream_get_bh_2(num_bits);
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return bitstream_get_bh_2(num_bits);
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#endif
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}
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}
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