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101 lines
4.0 KiB
C
101 lines
4.0 KiB
C
/* Copyright 2013 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Function to find backward reference copies. */
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#ifndef BROTLI_ENC_BACKWARD_REFERENCES_H_
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#define BROTLI_ENC_BACKWARD_REFERENCES_H_
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#include "../common/constants.h"
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#include <brotli/types.h>
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#include "./command.h"
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#include "./hash.h"
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#include "./memory.h"
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#include "./port.h"
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#include "./quality.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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/* "commands" points to the next output command to write to, "*num_commands" is
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initially the total amount of commands output by previous
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CreateBackwardReferences calls, and must be incremented by the amount written
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by this call. */
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BROTLI_INTERNAL void BrotliCreateBackwardReferences(
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MemoryManager* m, size_t num_bytes, size_t position, BROTLI_BOOL is_last,
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const uint8_t* ringbuffer, size_t ringbuffer_mask,
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const BrotliEncoderParams* params, Hashers* hashers, int* dist_cache,
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size_t* last_insert_len, Command* commands, size_t* num_commands,
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size_t* num_literals);
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typedef struct ZopfliNode {
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/* best length to get up to this byte (not including this byte itself)
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highest 8 bit is used to reconstruct the length code */
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uint32_t length;
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/* distance associated with the length
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highest 7 bit contains distance short code + 1 (or zero if no short code)
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*/
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uint32_t distance;
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/* number of literal inserts before this copy */
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uint32_t insert_length;
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/* This union holds information used by dynamic-programming. During forward
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pass |cost| it used to store the goal function. When node is processed its
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|cost| is invalidated in favor of |shortcut|. On path backtracing pass
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|next| is assigned the offset to next node on the path. */
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union {
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/* Smallest cost to get to this byte from the beginning, as found so far. */
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float cost;
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/* Offset to the next node on the path. Equals to command_length() of the
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next node on the path. For last node equals to BROTLI_UINT32_MAX */
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uint32_t next;
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/* Node position that provides next distance for distance cache. */
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uint32_t shortcut;
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} u;
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} ZopfliNode;
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BROTLI_INTERNAL void BrotliInitZopfliNodes(ZopfliNode* array, size_t length);
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/* Computes the shortest path of commands from position to at most
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position + num_bytes.
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On return, path->size() is the number of commands found and path[i] is the
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length of the ith command (copy length plus insert length).
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Note that the sum of the lengths of all commands can be less than num_bytes.
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On return, the nodes[0..num_bytes] array will have the following
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"ZopfliNode array invariant":
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For each i in [1..num_bytes], if nodes[i].cost < kInfinity, then
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(1) nodes[i].copy_length() >= 2
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(2) nodes[i].command_length() <= i and
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(3) nodes[i - nodes[i].command_length()].cost < kInfinity */
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BROTLI_INTERNAL size_t BrotliZopfliComputeShortestPath(
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MemoryManager* m, size_t num_bytes, size_t position,
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const uint8_t* ringbuffer, size_t ringbuffer_mask,
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const BrotliEncoderParams* params, const size_t max_backward_limit,
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const int* dist_cache, H10* hasher, ZopfliNode* nodes);
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BROTLI_INTERNAL void BrotliZopfliCreateCommands(const size_t num_bytes,
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const size_t block_start,
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const size_t max_backward_limit,
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const ZopfliNode* nodes,
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int* dist_cache,
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size_t* last_insert_len,
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Command* commands,
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size_t* num_literals);
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/* Maximum distance, see section 9.1. of the spec. */
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static BROTLI_INLINE size_t MaxBackwardLimit(int lgwin) {
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return (1u << lgwin) - BROTLI_WINDOW_GAP;
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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} /* extern "C" */
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#endif
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#endif /* BROTLI_ENC_BACKWARD_REFERENCES_H_ */
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