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