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/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Function to find backward reference copies. */
#ifndef BROTLI_ENC_BACKWARD_REFERENCES_H_
#define BROTLI_ENC_BACKWARD_REFERENCES_H_
#include "../common/types.h"
#include "./command.h"
#include "./hash.h"
#include "./memory.h"
#include "./port.h"
#include "./quality.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
/* "commands" points to the next output command to write to, "*num_commands" is
initially the total amount of commands output by previous
CreateBackwardReferences calls, and must be incremented by the amount written
by this call. */
BROTLI_INTERNAL void BrotliCreateBackwardReferences(
MemoryManager* m, size_t num_bytes, size_t position, BROTLI_BOOL is_last,
const uint8_t* ringbuffer, size_t ringbuffer_mask,
const BrotliEncoderParams* params, Hashers* hashers, int* dist_cache,
size_t* last_insert_len, Command* commands, size_t* num_commands,
size_t* num_literals);
typedef struct ZopfliNode {
/* best length to get up to this byte (not including this byte itself)
highest 8 bit is used to reconstruct the length code */
uint32_t length;
/* distance associated with the length
highest 7 bit contains distance short code + 1 (or zero if no short code)
*/
uint32_t distance;
/* number of literal inserts before this copy */
uint32_t insert_length;
/* This union holds information used by dynamic-programming. During forward
pass |cost| it used to store the goal function. When node is processed its
|cost| is invalidated in favor of |shortcut|. On path backtracing pass
|next| is assigned the offset to next node on the path. */
union {
/* Smallest cost to get to this byte from the beginning, as found so far. */
float cost;
/* Offset to the next node on the path. Equals to command_length() of the
next node on the path. For last node equals to BROTLI_UINT32_MAX */
uint32_t next;
/* Node position that provides next distance for distance cache. */
uint32_t shortcut;
} u;
} ZopfliNode;
BROTLI_INTERNAL void BrotliInitZopfliNodes(ZopfliNode* array, size_t length);
/* Computes the shortest path of commands from position to at most
position + num_bytes.
On return, path->size() is the number of commands found and path[i] is the
length of the ith command (copy length plus insert length).
Note that the sum of the lengths of all commands can be less than num_bytes.
On return, the nodes[0..num_bytes] array will have the following
"ZopfliNode array invariant":
For each i in [1..num_bytes], if nodes[i].cost < kInfinity, then
(1) nodes[i].copy_length() >= 2
(2) nodes[i].command_length() <= i and
(3) nodes[i - nodes[i].command_length()].cost < kInfinity */
BROTLI_INTERNAL size_t BrotliZopfliComputeShortestPath(
MemoryManager* m, size_t num_bytes, size_t position,
const uint8_t* ringbuffer, size_t ringbuffer_mask,
const BrotliEncoderParams* params, const size_t max_backward_limit,
const int* dist_cache, H10* hasher, ZopfliNode* nodes);
BROTLI_INTERNAL void BrotliZopfliCreateCommands(const size_t num_bytes,
const size_t block_start,
const size_t max_backward_limit,
const ZopfliNode* nodes,
int* dist_cache,
size_t* last_insert_len,
Command* commands,
size_t* num_literals);
/* Maximum distance, see section 9.1. of the spec. */
static BROTLI_INLINE size_t MaxBackwardLimit(int lgwin) {
return (1u << lgwin) - 16;
}
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif
#endif /* BROTLI_ENC_BACKWARD_REFERENCES_H_ */
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