52 lines
1.6 KiB
C
52 lines
1.6 KiB
C
/*
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Copyright 2011 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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Author: lode.vandevenne@gmail.com (Lode Vandevenne)
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Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
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*/
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/*
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Utilities for creating and using Huffman trees.
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*/
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#ifndef ZOPFLI_TREE_H_
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#define ZOPFLI_TREE_H_
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#include <string.h>
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/*
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Calculates the bitlengths for the Huffman tree, based on the counts of each
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symbol.
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*/
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void ZopfliCalculateBitLengths(const size_t* count, size_t n, int maxbits,
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unsigned *bitlengths);
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/*
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Converts a series of Huffman tree bitlengths, to the bit values of the symbols.
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*/
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void ZopfliLengthsToSymbols(const unsigned* lengths, size_t n, unsigned maxbits,
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unsigned* symbols);
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/*
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Calculates the entropy of each symbol, based on the counts of each symbol. The
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result is similar to the result of ZopfliCalculateBitLengths, but with the
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actual theoritical bit lengths according to the entropy. Since the resulting
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values are fractional, they cannot be used to encode the tree specified by
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DEFLATE.
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*/
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void ZopfliCalculateEntropy(const size_t* count, size_t n, double* bitlengths);
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#endif /* ZOPFLI_TREE_H_ */
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