76 lines
2.0 KiB
C++
76 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 <string.h>
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#include "huffman_helper.h"
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#include "bit_helper.h"
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bool HuffmanHelper::countSymbols(
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unsigned(&nextCode)[MAX_BL + 2],
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unsigned char& minLength,
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unsigned char& maxLength,
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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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if (symbolCount < 1 || symbolCount >= 1024) {
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return false;
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}
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unsigned short blCount[MAX_BL + 2];
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// Count symbol frequencies
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memset(blCount, 0, sizeof(blCount));
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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 > MAX_BL + 1) {
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return false;
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}
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blCount[l]++;
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}
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for (minLength = 1; minLength <= MAX_BL + 1; ++minLength) {
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if (blCount[minLength]) {
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break;
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}
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}
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for (maxLength = MAX_BL + 1; maxLength >= minLength; --maxLength) {
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if (blCount[maxLength]) {
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break;
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}
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}
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if (minLength > maxLength) {
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return false;
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}
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// Remove deleted symbols
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blCount[0] = 0;
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if (disableZeroBitSymbols) {
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blCount[1] = 0;
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}
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// Calculate start codes
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unsigned code = 0;
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for (unsigned i = minLength; i <= maxLength; ++i) {
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code = (code + blCount[i - 1]) << 1;
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nextCode[i] = code;
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}
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if (minLength == maxLength && blCount[maxLength] == 1) {
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return true;
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}
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// Check that we don't have holes
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return nextCode[maxLength] + blCount[maxLength] == (unsigned)(1 << (maxLength - 1));
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}
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