/*

* 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;

}

}  // namespace

/*

* Update an Adler32 Checksum

*/

void Adler32::add_data(std::span<const uint8_t> input) {

   const size_t PROCESS_AMOUNT = 5552;

   while(input.size() >= PROCESS_AMOUNT) {

      adler32_update(input.data(), PROCESS_AMOUNT, m_S1, m_S2);

      input = input.last(input.size() - PROCESS_AMOUNT);

   }

   adler32_update(input.data(), input.size(), m_S1, m_S2);

}

/*

* Finalize an Adler32 Checksum

*/

void Adler32::final_result(std::span<uint8_t> output) {

   store_be(output.data(), m_S2, m_S1);

   clear();

}

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

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

}

}  // namespace Botan