base64.cpp

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/*************************************************
* Base64 Encoder/Decoder Source File             *
* (C) 1999-2002 The Botan Project                *
*************************************************/

#include <botan/base64.h>

namespace Botan {

/*************************************************
* Base64_Encoder Constructor                     *
*************************************************/
Base64_Encoder::Base64_Encoder(bool breaks, u32bit length) :
   LINEBREAKS(breaks), LINELENGTH(length),
   in_buffer(48), out_buffer(4)
   {
   counter = position = 0;
   if(LINEBREAKS && (LINELENGTH == 0))
      throw Invalid_Argument("Base64_Encoder: Output lines cannot be zero "
                             "characters long");
   }

/*************************************************
* Base64 Encoding Operation                      *
*************************************************/
void Base64_Encoder::encode(const byte in[3], byte out[4])
   {
   static const byte BIN_TO_BASE64[] =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
   out[0] = BIN_TO_BASE64[((in[0] & 0xFC) >> 2)];
   out[1] = BIN_TO_BASE64[((in[0] & 0x03) << 4) | (in[1] >> 4)];
   out[2] = BIN_TO_BASE64[((in[1] & 0x0F) << 2) | (in[2] >> 6)];
   out[3] = BIN_TO_BASE64[((in[2] & 0x3F)     )];
   }

/*************************************************
* Encode and send a block                        *
*************************************************/
void Base64_Encoder::encode_and_send(const byte block[], u32bit length)
   {
   for(u32bit j = 0; j != length; j += 3)
      {
      encode(block + j, out_buffer);
      do_output(out_buffer, 4);
      }
   }

/*************************************************
* Handle the output                              *
*************************************************/
void Base64_Encoder::do_output(const byte input[], u32bit length)
   {
   if(LINEBREAKS)
      {
      u32bit remaining = length, offset = 0;
      while(remaining)
         {
         u32bit sent = std::min(LINELENGTH - counter, remaining);
         send(input + offset, sent);
         counter += sent;
         remaining -= sent;
         offset += sent;
         if(counter == LINELENGTH)
            {
            send('\n');
            counter = 0;
            }
         }
      }
   else
      send(input, length);
   }

/*************************************************
* Convert some data into Base64                  *
*************************************************/
void Base64_Encoder::write(const byte input[], u32bit length)
   {
   in_buffer.copy(position, input, length);
   if(position + length >= in_buffer.size())
      {
      encode_and_send(in_buffer, in_buffer.size());
      input += (in_buffer.size() - position);
      length -= (in_buffer.size() - position);
      while(length >= in_buffer.size())
         {
         encode_and_send(input, in_buffer.size());
         input += in_buffer.size();
         length -= in_buffer.size();
         }
      in_buffer.copy(input, length);
      position = 0;
      }
   position += length;
   }

/*************************************************
* Flush buffers                                  *
*************************************************/
void Base64_Encoder::end_msg()
   {
   u32bit start_of_last_block = 3 * (position / 3),
          left_over = position % 3;
   encode_and_send(in_buffer, start_of_last_block);

   if(left_over)
      {
      SecureBuffer<byte, 3> remainder(in_buffer + start_of_last_block,
                                      left_over);

      encode(remainder, out_buffer);

      u32bit empty_bits = 8 * (3 - left_over),
             index = 4 - 1;
      while(empty_bits >= 8)
         {
         out_buffer[index--] = '=';
         empty_bits -= 6;
         }

      do_output(out_buffer, 4);
      }

   if(counter && LINEBREAKS)
      send('\n');

   counter = position = 0;
   }

/*************************************************
* Base64_Decoder Constructor                     *
*************************************************/
Base64_Decoder::Base64_Decoder() : in_buffer(48), out_buffer(3)
   {
   position = 0;
   }

/*************************************************
* Base64 Decoding Operation                      *
*************************************************/
void Base64_Decoder::decode(const byte in[4], byte out[3])
   {
   out[0] = (byte)((BASE64_TO_BIN[in[0]] << 2) | (BASE64_TO_BIN[in[1]] >> 4));
   out[1] = (byte)((BASE64_TO_BIN[in[1]] << 4) | (BASE64_TO_BIN[in[2]] >> 2));
   out[2] = (byte)((BASE64_TO_BIN[in[2]] << 6) | (BASE64_TO_BIN[in[3]]));
   }

/*************************************************
* Decode and send a block                        *
*************************************************/
void Base64_Decoder::decode_and_send(const byte block[], u32bit length)
   {
   for(u32bit j = 0; j != length; j += 4)
      {
      decode(block + j, out_buffer);
      send(out_buffer, 3);
      }
   }

/*************************************************
* Convert some data from Base64                  *
*************************************************/
void Base64_Decoder::write(const byte input[], u32bit length)
   {
   for(u32bit j = 0; j != length; j++)
      {
      if(is_valid(input[j]))
         in_buffer[position++] = input[j];
      if(position == in_buffer.size())
         {
         decode_and_send(in_buffer, in_buffer.size());
         position = 0;
         }
      }
   }

/*************************************************
* Flush buffers                                  *
*************************************************/
void Base64_Decoder::end_msg()
   {
   if(position != 0)
      {
      u32bit start_of_last_block = 4 * (position / 4),
             left_over = position % 4;
      decode_and_send(in_buffer, start_of_last_block);

      if(left_over)
         {
         SecureBuffer<byte, 4> remainder(in_buffer + start_of_last_block,
                                         left_over);
         decode(remainder, out_buffer);
         send(out_buffer, ((left_over == 1) ? (1) : (left_over - 1)));
         }
      }
   position = 0;
   }

}