/*

* Adler32

* (C) 1999-2007 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/internal/adler32.h>

#include <botan/internal/loadstor.h>

namespace Botan {

namespace {

void adler32_update(const uint8_t input[], size_t length,

                    uint16_t& S1, uint16_t& S2)

   {

   uint32_t S1x = S1;

   uint32_t 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 uint8_t input[], size_t length)

   {

   const size_t PROCESS_AMOUNT = 5552;

   while(length >= PROCESS_AMOUNT)

      {

      adler32_update(input, PROCESS_AMOUNT, m_S1, m_S2);

      input += PROCESS_AMOUNT;

      length -= PROCESS_AMOUNT;

      }

   adler32_update(input, length, m_S1, m_S2);

   }

/*

* Finalize an Adler32 Checksum

*/

void Adler32::final_result(uint8_t output[])

   {

   store_be(output, m_S2, m_S1);

   clear();

   }

std::unique_ptr<HashFunction> Adler32::copy_state() const

   {

   return std::make_unique<Adler32>(*this);

   }

}