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