godot/thirdparty/libwebp/src/utils/huffman_utils.h

// Copyright 2012 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Utilities for building and looking up Huffman trees.
//
// Author: Urvang Joshi ([email protected])

#ifndef WEBP_UTILS_HUFFMAN_UTILS_H_
#define WEBP_UTILS_HUFFMAN_UTILS_H_

#include <assert.h>
#include "src/webp/format_constants.h"
#include "src/webp/types.h"

#ifdef __cplusplus
extern "C" {
#endif

#define HUFFMAN_TABLE_BITS …
#define HUFFMAN_TABLE_MASK …

#define LENGTHS_TABLE_BITS …
#define LENGTHS_TABLE_MASK …


// Huffman lookup table entry
HuffmanCode;

// long version for holding 32b values
HuffmanCode32;

// Contiguous memory segment of HuffmanCodes.
HuffmanTablesSegment;

// Chained memory segments of HuffmanCodes.
HuffmanTables;

// Allocates a HuffmanTables with 'size' contiguous HuffmanCodes. Returns 0 on
// memory allocation error, 1 otherwise.
WEBP_NODISCARD int VP8LHuffmanTablesAllocate(int size,
                                             HuffmanTables* huffman_tables);
void VP8LHuffmanTablesDeallocate(HuffmanTables* const huffman_tables);

#define HUFFMAN_PACKED_BITS …
#define HUFFMAN_PACKED_TABLE_SIZE …

// Huffman table group.
// Includes special handling for the following cases:
//  - is_trivial_literal: one common literal base for RED/BLUE/ALPHA (not GREEN)
//  - is_trivial_code: only 1 code (no bit is read from bitstream)
//  - use_packed_table: few enough literal symbols, so all the bit codes
//    can fit into a small look-up table packed_table[]
// The common literal base, if applicable, is stored in 'literal_arb'.
HTreeGroup;
struct HTreeGroup { … };

// Creates the instance of HTreeGroup with specified number of tree-groups.
WEBP_NODISCARD HTreeGroup* VP8LHtreeGroupsNew(int num_htree_groups);

// Releases the memory allocated for HTreeGroup.
void VP8LHtreeGroupsFree(HTreeGroup* const htree_groups);

// Builds Huffman lookup table assuming code lengths are in symbol order.
// The 'code_lengths' is pre-allocated temporary memory buffer used for creating
// the huffman table.
// Returns built table size or 0 in case of error (invalid tree or
// memory error).
WEBP_NODISCARD int VP8LBuildHuffmanTable(HuffmanTables* const root_table,
                                         int root_bits,
                                         const int code_lengths[],
                                         int code_lengths_size);

#ifdef __cplusplus
}    // extern "C"
#endif

#endif  // WEBP_UTILS_HUFFMAN_UTILS_H_