66 lines
2.0 KiB
C++
66 lines
2.0 KiB
C++
/* Copyright 2018 Dirk Steinke
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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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#include "pch.h"
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#include <algorithm>
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#include "huffman_encoder.h"
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#include "huffman_helper.h"
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#include "bit_helper.h"
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HuffmanEncoder::HuffmanEncoder(
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const unsigned char* symbolBitLengths,
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const unsigned symbolCount,
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const bool disableZeroBitSymbols
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) : _error(false) {
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if (!_constructTables(symbolBitLengths, symbolCount, disableZeroBitSymbols)) {
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_constructErrorTable(symbolCount);
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}
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}
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bool HuffmanEncoder::_constructTables(
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const unsigned char* symbolBitLengths,
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const unsigned symbolCount,
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const bool disableZeroBitSymbols
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) {
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unsigned nextCode[HuffmanHelper::MAX_BL + 2];
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unsigned char minLength, maxLength;
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if (!HuffmanHelper::countSymbols(nextCode, minLength, maxLength,
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symbolBitLengths, symbolCount,
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disableZeroBitSymbols)) {
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return false;
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}
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unsigned char minL = disableZeroBitSymbols ? 2 : 1;
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_lookup.resize(symbolCount);
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for (unsigned i = 0; i < symbolCount; ++i) {
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unsigned char l = (unsigned char)(symbolBitLengths[i] + 1);
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if (l < minL) {
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_lookup[i] = 0;
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continue;
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}
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unsigned char k = l - 1;
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unsigned code = bitReverse(nextCode[l]++, k);
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_lookup[i] = (code << 5) | k;
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}
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return true;
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}
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void HuffmanEncoder::_constructErrorTable(
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const unsigned symbolCount
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) {
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_error = true;
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_lookup.resize(symbolCount);
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std::fill(_lookup.begin(), _lookup.end(), 0);
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}
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