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minor optimizations to FLAC__bitbuffer_read_rice_signed_block()

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This commit is contained in:
Josh Coalson 2007-03-17 05:21:36 +00:00
parent 099a2893da
commit c63cf41ccc
1 changed files with 11 additions and 8 deletions
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19
src/libFLAC/bitreader.c
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@ -131,6 +131,7 @@ static const unsigned char byte_to_unary_table[] = {
#define FLaC__INLINE
#endif
/* WATCHOUT: assembly routines rely on the order in which these fields are declared */
struct FLAC__BitReader {
/* any partially-consumed word at the head will stay right-justified as bits are consumed from the left */
/* any incomplete word at the tail will be left-justified, and bytes from the read callback are added on the right */
@ -138,7 +139,8 @@ struct FLAC__BitReader {
unsigned capacity; /* in words */
unsigned words; /* # of completed words in buffer */
unsigned bytes; /* # of bytes in incomplete word at buffer[words] */
unsigned consumed_words, consumed_bits; /* #words+(#bits of head word) already consumed from the front of buffer */
unsigned consumed_words; /* #words ... */
unsigned consumed_bits; /* ... + (#bits of head word) already consumed from the front of buffer */
unsigned read_crc16; /* the running frame CRC */
unsigned crc16_align; /* the number of bits in the current consumed word that should not be CRC'd */
FLAC__BitReaderReadCallback read_callback;
@ -201,7 +203,8 @@ static FLaC__INLINE void crc16_update_word_(FLAC__BitReader *br, brword word)
br->crc16_align = 0;
}
static FLAC__bool bitreader_read_from_client_(FLAC__BitReader *br)
/* would be static except it needs to be called by asm routines */
FLAC__bool bitreader_read_from_client_(FLAC__BitReader *br)
{
unsigned start, end;
size_t bytes;
@ -827,7 +830,7 @@ FLAC__bool FLAC__bitreader_read_rice_signed_block(FLAC__BitReader *br, int vals[
/* WATCHOUT: code does not work with <32bit words; we can make things much faster with this assertion */
FLAC__ASSERT(FLAC__BITS_PER_WORD >= 32);
FLAC__ASSERT(parameter < 32);
/* the above two asserts also guarantee that the binary part never straddles more that 2 words, so we don't have to loop to read it */
/* the above two asserts also guarantee that the binary part never straddles more than 2 words, so we don't have to loop to read it */
if(nvals == 0)
return true;
@ -849,9 +852,9 @@ FLAC__bool FLAC__bitreader_read_rice_signed_block(FLAC__BitReader *br, int vals[
i = ALIGNED_UNARY_BITS(b);
#endif
uval += i;
bits = parameter;
i++;
cbits += i;
bits = parameter;
cbits++; /* skip over stop bit */
if(cbits == FLAC__BITS_PER_WORD) {
crc16_update_word_(br, br->buffer[cwords]);
cwords++;
@ -876,7 +879,7 @@ FLAC__bool FLAC__bitreader_read_rice_signed_block(FLAC__BitReader *br, int vals[
*/
if(br->bytes) {
const unsigned end = br->bytes * 8;
brword b = (br->buffer[cwords] & (FLAC__WORD_ALL_ONES << (FLAC__BITS_PER_WORD-end))) << cbits;
brword b = (br->buffer[cwords] & ~(FLAC__WORD_ALL_ONES >> end)) << cbits;
if(b) {
#if 0 /* too slow, but this is the idea: */
for(i = 0; !(b & FLAC__WORD_TOP_BIT_ONE); i++)
@ -885,9 +888,9 @@ FLAC__bool FLAC__bitreader_read_rice_signed_block(FLAC__BitReader *br, int vals[
i = ALIGNED_UNARY_BITS(b);
#endif
uval += i;
bits = parameter;
i++;
cbits += i;
bits = parameter;
cbits++; /* skip over stop bit */
FLAC__ASSERT(cbits < FLAC__BITS_PER_WORD);
goto break1;
}