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