/* base85.c - Don Yang (uguu.org)

   08/04/12
                                                                           */

#include<stdio.h>
#include<stdlib.h>

static void Encode(unsigned int input, char *output)
{
   unsigned int x;
   int i;

   output += 4;
   for(i = 0; i < 5; i++)
   {
      x = input % 85;
      input /= 85;
      *output = (x <= 31 ? x + 95 : x + 6);
      output--;
   }
}

static void Decode(char *input, unsigned int *output)
{
   int i;

   *output = 0;
   for(i = 0; i < 5; i++)
   {
      *output = (83 + *input) % 89 + 85 * *output;
      input++;
   }
}

static void Test(unsigned int value)
{
   char encode_buffer[5];
   unsigned int decode_value;

   Encode(value, encode_buffer);
   Decode(encode_buffer, &decode_value);
   if( value != decode_value )
   {
      printf("%08x -> %c%c%c%c%c %02x%02x%02x%02x%02x -> %08x\n",
             value,
             encode_buffer[0],
             encode_buffer[1],
             encode_buffer[2],
             encode_buffer[3],
             encode_buffer[4],
             encode_buffer[0],
             encode_buffer[1],
             encode_buffer[2],
             encode_buffer[3],
             encode_buffer[4],
             decode_value);
      exit(EXIT_FAILURE);
   }
}

static void EncodeCommandLine(int argc, char **argv)
{
   char encoded[5];
   unsigned int buffer, size;
   int i, j;

   buffer = size = 0;
   for(i = 1; i < argc; i++)
   {
      for(j = 0; argv[i][j] != '\0'; j++)
      {
         buffer |= argv[i][j] << (8 * size);
         size++;
         if( size == 4 )
         {
            Encode(buffer, encoded);
            fwrite(encoded, 5, 1, stdout);
            buffer = size = 0;
         }
      }
   }
   if( size != 0 )
   {
      Encode(buffer, encoded);
      fwrite(encoded, 5, 1, stdout);
      putchar(size == 1 ? '!' :
              size == 2 ? '%' :
                          '$');
   }
   else
   {
      putchar('#');
   }
   putchar('\n');
}

int main(int argc, char **argv)
{
   int i;

   if( argc > 1 )
   {
      EncodeCommandLine(argc, argv);
      return 0;
   }

   Test(0x33323130);
   Test(0x37363534);
   Test(0x62613938);
   Test(0x66656463);
   for(i = 0; i < 85; i++)
   {
      Test(i * 85);
      Test(i * 85 * 85);
      Test(i * 85 * 85 * 85);
   }
   for(i = 0; i < 0x10000; i++)
      Test(i);
   for(; i < 0x10000000; i += 0x100)
      Test(i);
   return 0;
}