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// File: crn_checksum.cpp
#include "crn_core.h"
namespace crnlib {
// From the public domain stb.h header.
uint adler32(const void* pBuf, size_t buflen, uint adler32) {
const uint8* buffer = static_cast<const uint8*>(pBuf);
const unsigned long ADLER_MOD = 65521;
unsigned long s1 = adler32 & 0xffff, s2 = adler32 >> 16;
size_t blocklen;
unsigned long i;
blocklen = buflen % 5552;
while (buflen) {
for (i = 0; i + 7 < blocklen; i += 8) {
s1 += buffer[0], s2 += s1;
s1 += buffer[1], s2 += s1;
s1 += buffer[2], s2 += s1;
s1 += buffer[3], s2 += s1;
s1 += buffer[4], s2 += s1;
s1 += buffer[5], s2 += s1;
s1 += buffer[6], s2 += s1;
s1 += buffer[7], s2 += s1;
buffer += 8;
}
for (; i < blocklen; ++i)
s1 += *buffer++, s2 += s1;
s1 %= ADLER_MOD, s2 %= ADLER_MOD;
buflen -= blocklen;
blocklen = 5552;
}
return (s2 << 16) + s1;
}
uint16 crc16(const void* pBuf, size_t len, uint16 crc) {
crc = ~crc;
const uint8* p = reinterpret_cast<const uint8*>(pBuf);
while (len) {
const uint16 q = *p++ ^ (crc >> 8);
crc <<= 8U;
uint16 r = (q >> 4) ^ q;
crc ^= r;
r <<= 5U;
crc ^= r;
r <<= 7U;
crc ^= r;
len--;
}
return static_cast<uint16>(~crc);
}
} // namespace crnlib
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