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