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Use fastpos.h when encoding LZMA dictionary size in

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Filter Flags encoder.
This commit is contained in:
Lasse Collin 2008-01-15 14:23:35 +02:00
parent e5728142a2
commit f10fc6a69d
1 changed files with 18 additions and 20 deletions
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38
src/liblzma/common/filter_flags_encoder.c
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@ -19,6 +19,7 @@
#include "common.h"
#include "lzma_encoder.h"
#include "fastpos.h"
/// \brief Calculates the size of the Filter Properties field
@ -204,35 +205,32 @@ properties_lzma(uint8_t *out, size_t *out_pos, size_t out_size,
// Dictionary flags
//
// Dictionary size is encoded using six bits of
// which one is mantissa and five are exponent.
// Dictionary size is encoded using similar encoding that is used
// internally by LZMA.
//
// There are some limits that must hold to keep
// this coding working.
# if LZMA_DICTIONARY_SIZE_MAX > UINT32_MAX / 2
# error LZMA_DICTIONARY_SIZE_MAX is too big.
# endif
// This won't work if dictionary size can be zero:
# if LZMA_DICTIONARY_SIZE_MIN < 1
# error LZMA_DICTIONARY_SIZE_MIN cannot be zero.
# endif
uint32_t d = options->dictionary_size;
// Validate it:
if (options->dictionary_size < LZMA_DICTIONARY_SIZE_MIN
|| options->dictionary_size > LZMA_DICTIONARY_SIZE_MAX)
if (d < LZMA_DICTIONARY_SIZE_MIN || d > LZMA_DICTIONARY_SIZE_MAX)
return LZMA_HEADER_ERROR;
if (options->dictionary_size == 1) {
// Special case
out[*out_pos] = 0x00;
} else {
// TODO This could be more elegant.
uint32_t i = 1;
while (((2 | ((i + 1) & 1)) << ((i - 1) / 2))
< options->dictionary_size)
++i;
out[*out_pos] = i;
}
// Round up to to the next 2^n or 2^n + 2^(n - 1) depending on which
// one is the next:
--d;
d |= d >> 2;
d |= d >> 3;
d |= d >> 4;
d |= d >> 8;
d |= d >> 16;
++d;
// Get the highest two bits using the proper encoding:
out[*out_pos] = get_pos_slot(d) - 1;
++*out_pos;
return LZMA_OK;