/*************************************************
* Adler32 Source File                            *
* (C) 1999-2007 The Botan Project                *
*************************************************/

#include <botan/adler32.h>
#include <botan/bit_ops.h>

namespace Botan {

/*************************************************
* Adler32 Checksum                               *
*************************************************/
void Adler32::hash(const byte input[], u32bit length)
   {
   u32bit S1x = S1, 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(u32bit j = 0; j != length; ++j)
      {
      S1x += input[j]; S2x += S1x;
      }
   S1x %= 65521;
   S2x %= 65521;
   S1 = S1x;
   S2 = S2x;
   }

/*************************************************
* Update an Adler32 Checksum                     *
*************************************************/
void Adler32::add_data(const byte input[], u32bit length)
   {
   const u32bit PROCESS_AMOUNT = 5552;
   while(length >= PROCESS_AMOUNT)
      {
      hash(input, PROCESS_AMOUNT);
      input += PROCESS_AMOUNT;
      length -= PROCESS_AMOUNT;
      }
   hash(input, length);
   }

/*************************************************
* Finalize an Adler32 Checksum                   *
*************************************************/
void Adler32::final_result(byte output[])
   {
   output[0] = get_byte(2, S2);
   output[1] = get_byte(3, S2);
   output[2] = get_byte(2, S1);
   output[3] = get_byte(3, S1);
   clear();
   }

}