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// adler32.cpp - originally written and placed in the public domain by Wei Dai
#include "pch.h"
#include "adler32.h"
NAMESPACE_BEGIN(CryptoPP)
void Adler32::Update(const byte *input, size_t length)
{
const unsigned long BASE = 65521;
unsigned long s1 = m_s1;
unsigned long s2 = m_s2;
if (length % 8 != 0)
{
do
{
s1 += *input++;
s2 += s1;
length--;
} while (length % 8 != 0);
if (s1 >= BASE)
s1 -= BASE;
s2 %= BASE;
}
while (length > 0)
{
s1 += input[0]; s2 += s1;
s1 += input[1]; s2 += s1;
s1 += input[2]; s2 += s1;
s1 += input[3]; s2 += s1;
s1 += input[4]; s2 += s1;
s1 += input[5]; s2 += s1;
s1 += input[6]; s2 += s1;
s1 += input[7]; s2 += s1;
length -= 8;
input += 8;
if (s1 >= BASE)
s1 -= BASE;
if (length % 0x8000 == 0)
s2 %= BASE;
}
CRYPTOPP_ASSERT(s1 < BASE);
CRYPTOPP_ASSERT(s2 < BASE);
m_s1 = (word16)s1;
m_s2 = (word16)s2;
}
void Adler32::TruncatedFinal(byte *hash, size_t size)
{
ThrowIfInvalidTruncatedSize(size);
switch (size)
{
default:
hash[3] = byte(m_s1);
// fall through
case 3:
hash[2] = byte(m_s1 >> 8);
// fall through
case 2:
hash[1] = byte(m_s2);
// fall through
case 1:
hash[0] = byte(m_s2 >> 8);
// fall through
case 0:
;;
// fall through
}
Reset();
}
NAMESPACE_END
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