#include <stdlib.h>
#include <strings.h>

#include "base64-internal.h"

static char encoding[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

void base64__encode_trail(const unsigned char *in, int nin, unsigned char *out)
{
 switch (nin)
  { case 1:
       out[0] = encoding[(in[0]>>2)&0x3f];
       out[1] = encoding[(in[0]<<4)&0x30];
       out[2] = '=';
       out[3] = '=';
       break;
    case 2:
       out[0] = encoding[(in[0]>>2)&0x3f];
       out[1] = encoding[((in[0]<<4)|(in[1]>>4))&0x3f];
       out[2] = encoding[(in[1]<<2)&0x3f];
       out[3] = '=';
       break;
    default:
       abort();
       break;
  }
}

void base64__encode(const unsigned char *in, unsigned char *out)
{
 out[0] = encoding[(in[0]>>2)&0x3f];
 out[1] = encoding[((in[0]<<4)|(in[1]>>4))&0x3f];
 out[2] = encoding[((in[1]<<2)|(in[2]>>6))&0x3f];
 out[3] = encoding[in[2]&0x3f];
}

static int encx(unsigned char c)
{
 const void *found;

 found = memchr(&encoding[0],c,64);
 return(found?((const char *)found)-&encoding[0]:-1);
}

B64DECSTATUS base64__decode(const unsigned char *in, unsigned char *out)
{
 unsigned int v;
 int d;

 d = encx(in[0]);
 if (d < 0) return(B64D_ERROR);
 v = d;
 d = encx(in[1]);
 if (d < 0) return(B64D_ERROR);
 v = (v << 6) | d;
 d = encx(in[2]);
 if (d < 0)
  { if ((in[2] == '=') && (in[3] == '=') && ((v & 0xf) == 0))
     { out[0] = v >> 4;
       return(B64D_FINAL_1);
     }
    return(B64D_ERROR);
  }
 v = (v << 6) | d;
 d = encx(in[3]);
 if (d < 0)
  { if ((in[3] == '=') && ((v & 0x3) == 0))
     { out[0] = v >> 10;
       out[1] = (v >> 2) & 0xff;
       return(B64D_FINAL_2);
     }
    return(B64D_ERROR);
  }
 out[0] = v >> 10;
 out[1] = (v >> 2) & 0xff;
 out[2] = ((v << 6) | d) & 0xff;
 return(B64D_NORMAL);
}