You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
123 lines
4.0 KiB
123 lines
4.0 KiB
4 months ago
|
/* Copyright 2010 Google Inc. All Rights Reserved.
|
||
|
|
|
||
|
|
Distributed under MIT license.
|
||
|
|
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Entropy encoding (Huffman) utilities. */
|
||
|
|
|
||
|
|
#ifndef BROTLI_ENC_ENTROPY_ENCODE_H_
|
||
|
|
#define BROTLI_ENC_ENTROPY_ENCODE_H_
|
||
|
|
|
||
|
|
#include "../common/platform.h"
|
||
|
|
#include <brotli/types.h>
|
||
|
|
|
||
|
|
#if defined(__cplusplus) || defined(c_plusplus)
|
||
|
|
extern "C" {
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/* A node of a Huffman tree. */
|
||
|
|
typedef struct HuffmanTree {
|
||
|
|
uint32_t total_count_;
|
||
|
|
int16_t index_left_;
|
||
|
|
int16_t index_right_or_value_;
|
||
|
|
} HuffmanTree;
|
||
|
|
|
||
|
|
static BROTLI_INLINE void InitHuffmanTree(HuffmanTree* self, uint32_t count,
|
||
|
|
int16_t left, int16_t right) {
|
||
|
|
self->total_count_ = count;
|
||
|
|
self->index_left_ = left;
|
||
|
|
self->index_right_or_value_ = right;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Returns 1 is assignment of depths succeeded, otherwise 0. */
|
||
|
|
BROTLI_INTERNAL BROTLI_BOOL BrotliSetDepth(
|
||
|
|
int p, HuffmanTree* pool, uint8_t* depth, int max_depth);
|
||
|
|
|
||
|
|
/* This function will create a Huffman tree.
|
||
|
|
|
||
|
|
The (data,length) contains the population counts.
|
||
|
|
The tree_limit is the maximum bit depth of the Huffman codes.
|
||
|
|
|
||
|
|
The depth contains the tree, i.e., how many bits are used for
|
||
|
|
the symbol.
|
||
|
|
|
||
|
|
The actual Huffman tree is constructed in the tree[] array, which has to
|
||
|
|
be at least 2 * length + 1 long.
|
||
|
|
|
||
|
|
See http://en.wikipedia.org/wiki/Huffman_coding */
|
||
|
|
BROTLI_INTERNAL void BrotliCreateHuffmanTree(const uint32_t* data,
|
||
|
|
const size_t length,
|
||
|
|
const int tree_limit,
|
||
|
|
HuffmanTree* tree,
|
||
|
|
uint8_t* depth);
|
||
|
|
|
||
|
|
/* Change the population counts in a way that the consequent
|
||
|
|
Huffman tree compression, especially its RLE-part will be more
|
||
|
|
likely to compress this data more efficiently.
|
||
|
|
|
||
|
|
length contains the size of the histogram.
|
||
|
|
counts contains the population counts.
|
||
|
|
good_for_rle is a buffer of at least length size */
|
||
|
|
BROTLI_INTERNAL void BrotliOptimizeHuffmanCountsForRle(
|
||
|
|
size_t length, uint32_t* counts, uint8_t* good_for_rle);
|
||
|
|
|
||
|
|
/* Write a Huffman tree from bit depths into the bit-stream representation
|
||
|
|
of a Huffman tree. The generated Huffman tree is to be compressed once
|
||
|
|
more using a Huffman tree */
|
||
|
|
BROTLI_INTERNAL void BrotliWriteHuffmanTree(const uint8_t* depth,
|
||
|
|
size_t num,
|
||
|
|
size_t* tree_size,
|
||
|
|
uint8_t* tree,
|
||
|
|
uint8_t* extra_bits_data);
|
||
|
|
|
||
|
|
/* Get the actual bit values for a tree of bit depths. */
|
||
|
|
BROTLI_INTERNAL void BrotliConvertBitDepthsToSymbols(const uint8_t* depth,
|
||
|
|
size_t len,
|
||
|
|
uint16_t* bits);
|
||
|
|
|
||
|
|
BROTLI_INTERNAL extern const size_t kBrotliShellGaps[6];
|
||
|
|
/* Input size optimized Shell sort. */
|
||
|
|
typedef BROTLI_BOOL (*HuffmanTreeComparator)(
|
||
|
|
const HuffmanTree*, const HuffmanTree*);
|
||
|
|
static BROTLI_INLINE void SortHuffmanTreeItems(HuffmanTree* items,
|
||
|
|
const size_t n, HuffmanTreeComparator comparator) {
|
||
|
|
if (n < 13) {
|
||
|
|
/* Insertion sort. */
|
||
|
|
size_t i;
|
||
|
|
for (i = 1; i < n; ++i) {
|
||
|
|
HuffmanTree tmp = items[i];
|
||
|
|
size_t k = i;
|
||
|
|
size_t j = i - 1;
|
||
|
|
while (comparator(&tmp, &items[j])) {
|
||
|
|
items[k] = items[j];
|
||
|
|
k = j;
|
||
|
|
if (!j--) break;
|
||
|
|
}
|
||
|
|
items[k] = tmp;
|
||
|
|
}
|
||
|
|
return;
|
||
|
|
} else {
|
||
|
|
/* Shell sort. */
|
||
|
|
int g = n < 57 ? 2 : 0;
|
||
|
|
for (; g < 6; ++g) {
|
||
|
|
size_t gap = kBrotliShellGaps[g];
|
||
|
|
size_t i;
|
||
|
|
for (i = gap; i < n; ++i) {
|
||
|
|
size_t j = i;
|
||
|
|
HuffmanTree tmp = items[i];
|
||
|
|
for (; j >= gap && comparator(&tmp, &items[j - gap]); j -= gap) {
|
||
|
|
items[j] = items[j - gap];
|
||
|
|
}
|
||
|
|
items[j] = tmp;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
#if defined(__cplusplus) || defined(c_plusplus)
|
||
|
|
} /* extern "C" */
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#endif /* BROTLI_ENC_ENTROPY_ENCODE_H_ */
|