74 lines
1.3 KiB
C++
74 lines
1.3 KiB
C++
#include "crc32.h"
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#include <QFile>
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Crc32::Crc32()
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{
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quint32 crc;
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// initialize CRC table
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for (int i = 0; i < 256; i++)
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{
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crc = i;
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for (int j = 0; j < 8; j++)
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crc = crc & 1 ? (crc >> 1) ^ 0xEDB88320UL : crc >> 1;
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crc_table[i] = crc;
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}
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}
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quint32 Crc32::calculateFromFile(QString filename)
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{
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quint32 crc;
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QFile file;
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char buffer[16000];
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int len, i;
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crc = 0xFFFFFFFFUL;
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file.setFileName(filename);
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if (file.open(QIODevice::ReadOnly))
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{
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while (!file.atEnd())
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{
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len = file.read(buffer, 16000);
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for (i = 0; i < len; i++)
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crc = crc_table[(crc ^ buffer[i]) & 0xFF] ^ (crc >> 8);
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}
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file.close();
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}
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return crc ^ 0xFFFFFFFFUL;
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}
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void Crc32::initInstance(int i)
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{
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instances[i] = 0xFFFFFFFFUL;
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}
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void Crc32::pushData(int i, char *data, int len)
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{
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quint32 crc = instances[i];
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if (crc)
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{
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for (int j = 0; j < len; j++)
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crc = crc_table[(crc ^ data[j]) & 0xFF] ^ (crc >> 8);
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instances[i] = crc;
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}
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}
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quint32 Crc32::releaseInstance(int i)
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{
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quint32 crc32 = instances[i];
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if (crc32) {
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instances.remove(i);
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return crc32 ^ 0xFFFFFFFFUL;
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}
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else {
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return 0;
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}
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}
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