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/*
* Adler32
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/adler32.h>
#include <botan/loadstor.h>
namespace Botan {
namespace {
void adler32_update(const byte input[], size_t length,
u16bit& S1, u16bit& S2)
{
u32bit S1x = S1;
u32bit S2x = S2;
while(length >= 16)
{
S1x += input[ 0]; S2x += S1x;
S1x += input[ 1]; S2x += S1x;
S1x += input[ 2]; S2x += S1x;
S1x += input[ 3]; S2x += S1x;
S1x += input[ 4]; S2x += S1x;
S1x += input[ 5]; S2x += S1x;
S1x += input[ 6]; S2x += S1x;
S1x += input[ 7]; S2x += S1x;
S1x += input[ 8]; S2x += S1x;
S1x += input[ 9]; S2x += S1x;
S1x += input[10]; S2x += S1x;
S1x += input[11]; S2x += S1x;
S1x += input[12]; S2x += S1x;
S1x += input[13]; S2x += S1x;
S1x += input[14]; S2x += S1x;
S1x += input[15]; S2x += S1x;
input += 16;
length -= 16;
}
for(size_t j = 0; j != length; ++j)
{
S1x += input[j];
S2x += S1x;
}
S1 = S1x % 65521;
S2 = S2x % 65521;
}
}
/*
* Update an Adler32 Checksum
*/
void Adler32::add_data(const byte input[], size_t length)
{
const size_t PROCESS_AMOUNT = 5552;
while(length >= PROCESS_AMOUNT)
{
adler32_update(input, PROCESS_AMOUNT, S1, S2);
input += PROCESS_AMOUNT;
length -= PROCESS_AMOUNT;
}
adler32_update(input, length, S1, S2);
}
/*
* Finalize an Adler32 Checksum
*/
void Adler32::final_result(byte output[])
{
store_be(output, S2, S1);
clear();
}
}
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