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bitwriter.c: Cleanups and fixups 

Assertions added, assertions simplified, unnecessary assignments
removed, mask calculations improved.

Patch-from: lvqcl <lvqcl.mail@gmail.com>
This commit is contained in:
Erik de Castro Lopo 2015-12-31 07:32:35 +11:00
parent cf7f1b5a02
commit 396999341a
1 changed files with 14 additions and 13 deletions
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27
src/libFLAC/bitwriter.c
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@ -322,6 +322,8 @@ inline FLAC__bool FLAC__bitwriter_write_raw_uint32(FLAC__BitWriter *bw, FLAC__ui
if(bw->capacity <= bw->words + bits && !bitwriter_grow_(bw, bits))
return false;
FLAC__ASSERT((bits == 32) || (val>>bits == 0));
left = FLAC__BITS_PER_WORD - bw->bits;
if(bits < left) {
bw->accum <<= bits;
@ -334,9 +336,7 @@ inline FLAC__bool FLAC__bitwriter_write_raw_uint32(FLAC__BitWriter *bw, FLAC__ui
bw->buffer[bw->words++] = SWAP_BE_WORD_TO_HOST(bw->accum);
bw->accum = val;
}
else {
bw->accum = val;
bw->bits = 0;
else { /* at this point bits == FLAC__BITS_PER_WORD == 32 and bw->bits == 0 */
bw->buffer[bw->words++] = SWAP_BE_WORD_TO_HOST(val);
}
@ -407,7 +407,7 @@ unsigned FLAC__bitwriter_rice_bits(FLAC__int32 val, unsigned parameter)
{
FLAC__uint32 uval;
FLAC__ASSERT(parameter < sizeof(unsigned)*8);
FLAC__ASSERT(parameter < 32);
/* fold signed to unsigned; actual formula is: negative(v)? -2v-1 : 2v */
uval = val;
@ -488,7 +488,7 @@ FLAC__bool FLAC__bitwriter_write_rice_signed(FLAC__BitWriter *bw, FLAC__int32 va
FLAC__ASSERT(0 != bw);
FLAC__ASSERT(0 != bw->buffer);
FLAC__ASSERT(parameter < 8*sizeof(uval));
FLAC__ASSERT(parameter < 32);
/* fold signed to unsigned; actual formula is: negative(v)? -2v-1 : 2v */
uval = val;
@ -511,16 +511,16 @@ FLAC__bool FLAC__bitwriter_write_rice_signed(FLAC__BitWriter *bw, FLAC__int32 va
FLAC__bool FLAC__bitwriter_write_rice_signed_block(FLAC__BitWriter *bw, const FLAC__int32 *vals, unsigned nvals, unsigned parameter)
{
const FLAC__uint32 mask1 = FLAC__WORD_ALL_ONES << parameter; /* we val|=mask1 to set the stop bit above it... */
const FLAC__uint32 mask2 = FLAC__WORD_ALL_ONES >> (31-parameter); /* ...then mask off the bits above the stop bit with val&=mask2*/
const FLAC__uint32 mask1 = (FLAC__uint32)0xffffffff << parameter; /* we val|=mask1 to set the stop bit above it... */
const FLAC__uint32 mask2 = (FLAC__uint32)0xffffffff >> (31-parameter); /* ...then mask off the bits above the stop bit with val&=mask2 */
FLAC__uint32 uval;
unsigned left;
const unsigned lsbits = 1 + parameter;
unsigned msbits;
unsigned msbits, total_bits;
FLAC__ASSERT(0 != bw);
FLAC__ASSERT(0 != bw->buffer);
FLAC__ASSERT(parameter < 8*sizeof(uint32_t)-1);
FLAC__ASSERT(parameter < 31);
/* WATCHOUT: code does not work with <32bit words; we can make things much faster with this assertion */
FLAC__ASSERT(FLAC__BITS_PER_WORD >= 32);
@ -531,19 +531,20 @@ FLAC__bool FLAC__bitwriter_write_rice_signed_block(FLAC__BitWriter *bw, const FL
uval ^= (*vals>>31);
msbits = uval >> parameter;
total_bits = lsbits + msbits;
if(bw->bits && bw->bits + msbits + lsbits < FLAC__BITS_PER_WORD) { /* i.e. if the whole thing fits in the current uint32_t */
if(bw->bits && bw->bits + total_bits < FLAC__BITS_PER_WORD) { /* i.e. if the whole thing fits in the current uint32_t */
/* ^^^ if bw->bits is 0 then we may have filled the buffer and have no free uint32_t to work in */
bw->bits = bw->bits + msbits + lsbits;
bw->bits += total_bits;
uval |= mask1; /* set stop bit */
uval &= mask2; /* mask off unused top bits */
bw->accum <<= msbits + lsbits;
bw->accum <<= total_bits;
bw->accum |= uval;
}
else {
/* slightly pessimistic size check but faster than "<= bw->words + (bw->bits+msbits+lsbits+FLAC__BITS_PER_WORD-1)/FLAC__BITS_PER_WORD" */
/* OPT: pessimism may cause flurry of false calls to grow_ which eat up all savings before it */
if(bw->capacity <= bw->words + bw->bits + msbits + 1/*lsbits always fit in 1 uint32_t*/ && !bitwriter_grow_(bw, msbits+lsbits))
if(bw->capacity <= bw->words + bw->bits + msbits + 1 /* lsbits always fit in 1 uint32_t */ && !bitwriter_grow_(bw, total_bits))
return false;
if(msbits) {