backward_references_hq.h (3773B)
1 /* Copyright 2013 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 to find backward reference copies. */ 8 9 #ifndef BROTLI_ENC_BACKWARD_REFERENCES_HQ_H_ 10 #define BROTLI_ENC_BACKWARD_REFERENCES_HQ_H_ 11 12 #include "../common/context.h" 13 #include "../common/platform.h" 14 #include "command.h" 15 #include "hash.h" 16 #include "memory.h" 17 #include "params.h" 18 19 #if defined(__cplusplus) || defined(c_plusplus) 20 extern "C" { 21 #endif 22 23 BROTLI_INTERNAL void BrotliCreateZopfliBackwardReferences(MemoryManager* m, 24 size_t num_bytes, 25 size_t position, const uint8_t* ringbuffer, size_t ringbuffer_mask, 26 ContextLut literal_context_lut, const BrotliEncoderParams* params, 27 Hasher* hasher, int* dist_cache, size_t* last_insert_len, 28 Command* commands, size_t* num_commands, size_t* num_literals); 29 30 BROTLI_INTERNAL void BrotliCreateHqZopfliBackwardReferences(MemoryManager* m, 31 size_t num_bytes, 32 size_t position, const uint8_t* ringbuffer, size_t ringbuffer_mask, 33 ContextLut literal_context_lut, const BrotliEncoderParams* params, 34 Hasher* hasher, int* dist_cache, size_t* last_insert_len, 35 Command* commands, size_t* num_commands, size_t* num_literals); 36 37 typedef struct ZopfliNode { 38 /* Best length to get up to this byte (not including this byte itself) 39 highest 7 bit is used to reconstruct the length code. */ 40 uint32_t length; 41 /* Distance associated with the length. */ 42 uint32_t distance; 43 /* Number of literal inserts before this copy; highest 5 bits contain 44 distance short code + 1 (or zero if no short code). */ 45 uint32_t dcode_insert_length; 46 47 /* This union holds information used by dynamic-programming. During forward 48 pass |cost| it used to store the goal function. When node is processed its 49 |cost| is invalidated in favor of |shortcut|. On path back-tracing pass 50 |next| is assigned the offset to next node on the path. */ 51 union { 52 /* Smallest cost to get to this byte from the beginning, as found so far. */ 53 float cost; 54 /* Offset to the next node on the path. Equals to command_length() of the 55 next node on the path. For last node equals to BROTLI_UINT32_MAX */ 56 uint32_t next; 57 /* Node position that provides next distance for distance cache. */ 58 uint32_t shortcut; 59 } u; 60 } ZopfliNode; 61 62 BROTLI_INTERNAL void BrotliInitZopfliNodes(ZopfliNode* array, size_t length); 63 64 /* Computes the shortest path of commands from position to at most 65 position + num_bytes. 66 67 On return, path->size() is the number of commands found and path[i] is the 68 length of the i-th command (copy length plus insert length). 69 Note that the sum of the lengths of all commands can be less than num_bytes. 70 71 On return, the nodes[0..num_bytes] array will have the following 72 "ZopfliNode array invariant": 73 For each i in [1..num_bytes], if nodes[i].cost < kInfinity, then 74 (1) nodes[i].copy_length() >= 2 75 (2) nodes[i].command_length() <= i and 76 (3) nodes[i - nodes[i].command_length()].cost < kInfinity */ 77 BROTLI_INTERNAL size_t BrotliZopfliComputeShortestPath( 78 MemoryManager* m, size_t num_bytes, 79 size_t position, const uint8_t* ringbuffer, size_t ringbuffer_mask, 80 ContextLut literal_context_lut, const BrotliEncoderParams* params, 81 const int* dist_cache, Hasher* hasher, ZopfliNode* nodes); 82 83 BROTLI_INTERNAL void BrotliZopfliCreateCommands( 84 const size_t num_bytes, const size_t block_start, const ZopfliNode* nodes, 85 int* dist_cache, size_t* last_insert_len, const BrotliEncoderParams* params, 86 Command* commands, size_t* num_literals); 87 88 #if defined(__cplusplus) || defined(c_plusplus) 89 } /* extern "C" */ 90 #endif 91 92 #endif /* BROTLI_ENC_BACKWARD_REFERENCES_HQ_H_ */