diff options
Diffstat (limited to 'src/inflate.c')
| -rw-r--r-- | src/inflate.c | 35 |
1 files changed, 16 insertions, 19 deletions
diff --git a/src/inflate.c b/src/inflate.c index 9fa7d8d..725d6b0 100644 --- a/src/inflate.c +++ b/src/inflate.c @@ -88,36 +88,33 @@ uint8_t deflate_hc_lengths[19]; /* * Code lengths of the literal/length and distance alphabets. + * up to 286 literal/length codes + up to 32 distance codes. */ uint8_t deflate_lld_lengths[318]; /* - * Assumptions: - * * huffman code length is limited to 11 bits - * * there are no more than 255 huffman codes with the same length - * - * Rationale: longer huffman codes might appear when handling large data - * sets. We don't do that; instead, we expect the uncompressed source to - * be no more than a few kB of data. - */ - -/* * Bit length counts and next code entries for Literal/Length alphabet. * Combined with the code lengths in deflate_lld_lengths, these make up the * Literal/Length alphabet. See the algorithm in RFC 1951 section 3.2.2 for * details. * - * In deflate, these variables are also used for the huffman alphabet in - * dynamic huffman blocks. + * Assumption: There are no more than 255 huffman codes with the same length. + * As the largest alphabet (the literal/length alphabet) contains just 288 + * codes in total, this should be reasonable. + * + * These variables are also used for the huffman alphabet in dynamic huffman + * blocks. */ -uint8_t deflate_bl_count_ll[12]; -uint16_t deflate_next_code_ll[12]; +uint8_t deflate_bl_count_ll[16]; +uint16_t deflate_next_code_ll[16]; /* - * Bit length counts and next code entries for Distance alphabet. + * Bit length counts and next code entries for Distance alphabet. Note that, + * even though there are just 30 different distance codes, individual + * codes may be up to 16 bits long. */ -uint8_t deflate_bl_count_d[12]; -uint16_t deflate_next_code_d[12]; +uint8_t deflate_bl_count_d[16]; +uint16_t deflate_next_code_d[16]; static uint16_t deflate_rev_word(uint16_t word, uint8_t bits) { @@ -168,7 +165,7 @@ static void deflate_build_alphabet(uint8_t * lengths, uint16_t size, uint16_t i; uint16_t code = 0; uint16_t max_len = 0; - for (i = 0; i < 12; i++) { + for (i = 0; i < 16; i++) { bl_count[i] = 0; } @@ -191,7 +188,7 @@ static uint16_t deflate_huff(uint8_t * lengths, uint16_t size, uint8_t * bl_count, uint16_t * next_code) { uint16_t next_word = deflate_get_word(); - for (uint8_t num_bits = 1; num_bits < 12; num_bits++) { + for (uint8_t num_bits = 1; num_bits < 16; num_bits++) { uint16_t next_bits = deflate_rev_word(next_word, num_bits); if (bl_count[num_bits] && next_bits >= next_code[num_bits] && next_bits < next_code[num_bits] + bl_count[num_bits]) { |