compress_fragment_two_pass.h (2852B)
1 /* Copyright 2015 Google Inc. All Rights Reserved. 2 3 Distributed under MIT license. 4 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT 5 */ 6 7 /* Function for fast encoding of an input fragment, independently from the input 8 history. This function uses two-pass processing: in the first pass we save 9 the found backward matches and literal bytes into a buffer, and in the 10 second pass we emit them into the bit stream using prefix codes built based 11 on the actual command and literal byte histograms. */ 12 13 #ifndef BROTLI_ENC_COMPRESS_FRAGMENT_TWO_PASS_H_ 14 #define BROTLI_ENC_COMPRESS_FRAGMENT_TWO_PASS_H_ 15 16 #include "../common/constants.h" 17 #include "../common/platform.h" 18 #include "entropy_encode.h" 19 20 #if defined(__cplusplus) || defined(c_plusplus) 21 extern "C" { 22 #endif 23 24 /* TODO(eustas): turn to macro. */ 25 static const size_t kCompressFragmentTwoPassBlockSize = 1 << 17; 26 27 typedef struct BrotliTwoPassArena { 28 uint32_t lit_histo[256]; 29 uint8_t lit_depth[256]; 30 uint16_t lit_bits[256]; 31 32 uint32_t cmd_histo[128]; 33 uint8_t cmd_depth[128]; 34 uint16_t cmd_bits[128]; 35 36 /* BuildAndStoreCommandPrefixCode */ 37 HuffmanTree tmp_tree[2 * BROTLI_NUM_LITERAL_SYMBOLS + 1]; 38 uint8_t tmp_depth[BROTLI_NUM_COMMAND_SYMBOLS]; 39 uint16_t tmp_bits[64]; 40 } BrotliTwoPassArena; 41 42 /* Compresses "input" string to the "*storage" buffer as one or more complete 43 meta-blocks, and updates the "*storage_ix" bit position. 44 45 If "is_last" is 1, emits an additional empty last meta-block. 46 47 REQUIRES: "input_size" is greater than zero, or "is_last" is 1. 48 REQUIRES: "input_size" is less or equal to maximal metablock size (1 << 24). 49 REQUIRES: "command_buf" and "literal_buf" point to at least 50 kCompressFragmentTwoPassBlockSize long arrays. 51 REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero. 52 REQUIRES: "table_size" is a power of two 53 OUTPUT: maximal copy distance <= |input_size| 54 OUTPUT: maximal copy distance <= BROTLI_MAX_BACKWARD_LIMIT(18) */ 55 BROTLI_INTERNAL void BrotliCompressFragmentTwoPass(BrotliTwoPassArena* s, 56 const uint8_t* input, 57 size_t input_size, 58 BROTLI_BOOL is_last, 59 uint32_t* command_buf, 60 uint8_t* literal_buf, 61 int* table, 62 size_t table_size, 63 size_t* storage_ix, 64 uint8_t* storage); 65 66 #if defined(__cplusplus) || defined(c_plusplus) 67 } /* extern "C" */ 68 #endif 69 70 #endif /* BROTLI_ENC_COMPRESS_FRAGMENT_TWO_PASS_H_ */