diff options
| -rw-r--r-- | src/liblzma/common/filter_flags_encoder.c | 40 |
1 files changed, 19 insertions, 21 deletions
diff --git a/src/liblzma/common/filter_flags_encoder.c b/src/liblzma/common/filter_flags_encoder.c index d8f260a1..2d11dd3a 100644 --- a/src/liblzma/common/filter_flags_encoder.c +++ b/src/liblzma/common/filter_flags_encoder.c @@ -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; |