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// Copyright 2013 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Utilities for building and looking up Huffman trees.
#ifndef BROTLI_DEC_HUFFMAN_H_
#define BROTLI_DEC_HUFFMAN_H_
#include <assert.h>
#include "./types.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
// A node of a Huffman tree.
typedef struct {
int symbol_;
int children_; // delta offset to both children (contiguous) or 0 if leaf.
} HuffmanTreeNode;
// Huffman Tree.
#define HUFF_LUT_BITS 7
#define HUFF_LUT (1U << HUFF_LUT_BITS)
typedef struct HuffmanTree HuffmanTree;
struct HuffmanTree {
// Fast lookup for short bit lengths.
uint8_t lut_bits_[HUFF_LUT];
int16_t lut_symbol_[HUFF_LUT];
int16_t lut_jump_[HUFF_LUT];
// Complete tree for lookups.
HuffmanTreeNode* root_; // all the nodes, starting at root.
int max_nodes_; // max number of nodes
int num_nodes_; // number of currently occupied nodes
};
// Returns true if the given node is not a leaf of the Huffman tree.
static BROTLI_INLINE int HuffmanTreeNodeIsNotLeaf(
const HuffmanTreeNode* const node) {
return node->children_;
}
// Go down one level. Most critical function. 'right_child' must be 0 or 1.
static BROTLI_INLINE const HuffmanTreeNode* HuffmanTreeNextNode(
const HuffmanTreeNode* node, int right_child) {
return node + node->children_ + right_child;
}
// Releases the nodes of the Huffman tree.
// Note: It does NOT free 'tree' itself.
void BrotliHuffmanTreeRelease(HuffmanTree* const tree);
// Builds Huffman tree assuming code lengths are implicitly in symbol order.
// Returns false in case of error (invalid tree or memory error).
int BrotliHuffmanTreeBuildImplicit(HuffmanTree* const tree,
const uint8_t* const code_lengths,
int code_lengths_size);
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif
#endif // BROTLI_DEC_HUFFMAN_H_
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