huffman.h - mozsearch

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// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#ifndef LIB_JPEGLI_HUFFMAN_H_

#define LIB_JPEGLI_HUFFMAN_H_

#include <stdint.h>

#include <stdlib.h>

#include "lib/jpegli/common_internal.h"

namespace jpegli {

constexpr int kJpegHuffmanRootTableBits = 8;

// Maximum huffman lookup table size.

// According to zlib/examples/enough.c, 758 entries are always enough for

// an alphabet of 257 symbols (256 + 1 special symbol for the all 1s code) and

// max bit length 16 if the root table has 8 bits.

constexpr int kJpegHuffmanLutSize = 758;

struct HuffmanTableEntry {

  uint8_t bits;    // number of bits used for this symbol

  uint16_t value;  // symbol value or table offset

};

void BuildJpegHuffmanTable(const uint32_t* count, const uint32_t* symbols,

                           HuffmanTableEntry* lut);

// 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.

//

// See http://en.wikipedia.org/wiki/Huffman_coding

void CreateHuffmanTree(const uint32_t* data, size_t length, int tree_limit,

                       uint8_t* depth);

void ValidateHuffmanTable(j_common_ptr cinfo, const JHUFF_TBL* table,

                          bool is_dc);

void AddStandardHuffmanTables(j_common_ptr cinfo, bool is_dc);

}  // namespace jpegli

#endif  // LIB_JPEGLI_HUFFMAN_H_