static const char rcsid[] = "#(@) $Id: base64.m,v 1.1 2007-08-30 21:14:02 gepo Exp $";

/*

	   Encode or decode file as MIME base64 (RFC 1341)

			    by John Walker
		       http://www.fourmilab.ch/

		This program is in the public domain.

*/
#include <stdio.h>
#include <ctype.h>
/*  ENCODE  --	Encode binary file into base64.  */
#include <stdlib.h>

#include "base64.h"

static unsigned char dtable[512];

void buffer_new(struct buffer_st *b)
{
  b->length = 512;
  b->data = malloc(sizeof(char)*(b->length));
  b->data[0] = 0;
  b->ptr = b->data;
  b->offset = 0;
}

void buffer_add(struct buffer_st *b, char c)
{
  *(b->ptr++) = c;
  b->offset++;
  if (b->offset == b->length) {
    b->length += 512;
    b->data = realloc(b->data, b->length);
    b->ptr = b->data + b->offset;
  }
}

void buffer_delete(struct buffer_st *b)
{
  free(b->data);
  b->length = 0;
  b->offset = 0;
  b->ptr = NULL;
  b->data = NULL;
}

void base64_encode(struct buffer_st *b, const char *source, int length)
{
  int i, hiteof = 0;
  int offset = 0;
  int olen;
  
  olen = 0;
  
  buffer_new(b);
  
  /*	Fill dtable with character encodings.  */
  
  for (i = 0; i < 26; i++) {
    dtable[i] = 'A' + i;
    dtable[26 + i] = 'a' + i;
  }
  for (i = 0; i < 10; i++) {
    dtable[52 + i] = '0' + i;
  }
  dtable[62] = '+';
  dtable[63] = '/';
  
  while (!hiteof) {
    unsigned char igroup[3], ogroup[4];
    int c, n;
    
    igroup[0] = igroup[1] = igroup[2] = 0;
    for (n = 0; n < 3; n++) {
      c = *(source++);
      offset++;
      if (offset > length) {
	hiteof = 1;
	break;
      }
      igroup[n] = (unsigned char) c;
    }
    if (n > 0) {
      ogroup[0] = dtable[igroup[0] >> 2];
      ogroup[1] = dtable[((igroup[0] & 3) << 4) | (igroup[1] >> 4)];
      ogroup[2] = dtable[((igroup[1] & 0xF) << 2) | (igroup[2] >> 6)];
      ogroup[3] = dtable[igroup[2] & 0x3F];
      
      /* Replace characters in output stream with "=" pad
	 characters if fewer than three characters were
	 read from the end of the input stream. */
      
      if (n < 3) {
	ogroup[3] = '=';
	if (n < 2) {
	  ogroup[2] = '=';
	}
      }
      for (i = 0; i < 4; i++) {
	buffer_add(b, ogroup[i]);
	if (!(b->offset % 72)) {
	  // buffer_add(b, '\r');
	  buffer_add(b, '\n');
	}
      }
    }
  }
  // buffer_add(b, '\r');
  buffer_add(b, '\n');
}

void base64_decode(struct buffer_st *bfr, const char *source, int length)
{
    int i;
    int offset = 0;
    int endoffile;
    int count;

    buffer_new(bfr);

    for (i = 0; i < 255; i++) {
	dtable[i] = 0x80;
    }
    for (i = 'A'; i <= 'Z'; i++) {
        dtable[i] = 0 + (i - 'A');
    }
    for (i = 'a'; i <= 'z'; i++) {
        dtable[i] = 26 + (i - 'a');
    }
    for (i = '0'; i <= '9'; i++) {
        dtable[i] = 52 + (i - '0');
    }
    dtable['+'] = 62;
    dtable['/'] = 63;
    dtable['='] = 0;

    endoffile = 0;

    /*CONSTANTCONDITION*/
    while (1) {
	unsigned char a[4], b[4], o[3];

	for (i = 0; i < 4; i++) {
	    int c;
	    while (1) {
	      c = *(source++);
	      offset++;
	      if (offset > length) endoffile = 1;
	      if (isspace(c) || c == '\n' || c == '\r') continue;
	      break;
	    }

	    if (endoffile) {
	      /*
		if (i > 0) {
                    fprintf(stderr, "Input file incomplete.\n");
		    exit(1);
		}
	      */
		return;
	    }

	    if (dtable[c] & 0x80) {
	      /*
	      fprintf(stderr, "Offset %i length %i\n", offset, length);
	      fprintf(stderr, "character '%c:%x:%c' in input file.\n", c, c, dtable[c]);
	      exit(1);
	      */
	      i--;
	      continue;
	    }
	    a[i] = (unsigned char) c;
	    b[i] = (unsigned char) dtable[c];
	}
	o[0] = (b[0] << 2) | (b[1] >> 4);
	o[1] = (b[1] << 4) | (b[2] >> 2);
	o[2] = (b[2] << 6) | b[3];
        i = a[2] == '=' ? 1 : (a[3] == '=' ? 2 : 3);
	count = 0;
	while (count < i) {
	  buffer_add(bfr, o[count++]);
	}
	if (i < 3) {
	    return;
	}
    }
}
