/*

 * base64.c

 * base64 encode/decode implementation

 *

 * Copyright (c) 2011 Nikias Bassen, All Rights Reserved.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 */

#include <string.h>

#include "base64.h"

static const char base64_str[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const char base64_pad = '=';

static const signed char base64_table[256] = {

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,

  52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,

  -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,

  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,

  -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,

  41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,

  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1

};

size_t base64encode(char *outbuf, const unsigned char *buf, size_t size)

{

  if (!outbuf || !buf || (size <= 0)) {

    return 0;

  }

  size_t n = 0;

  size_t m = 0;

  unsigned char input[3];

  unsigned int output[4];

  while (n < size) {

    input[0] = buf[n];

    input[1] = (n+1 < size) ? buf[n+1] : 0;

    input[2] = (n+2 < size) ? buf[n+2] : 0;

    output[0] = input[0] >> 2;

    output[1] = ((input[0] & 3) << 4) + (input[1] >> 4);

    output[2] = ((input[1] & 15) << 2) + (input[2] >> 6);

    output[3] = input[2] & 63;

    outbuf[m++] = base64_str[(int)output[0]];

    outbuf[m++] = base64_str[(int)output[1]];

    outbuf[m++] = (n+1 < size) ? base64_str[(int)output[2]] : base64_pad;

    outbuf[m++] = (n+2 < size) ? base64_str[(int)output[3]] : base64_pad;

    n+=3;

  }

  outbuf[m] = 0; // 0-termination!

  return m;

}

unsigned char *base64decode(const char *buf, size_t *size)

{

  if (!buf || !size) return NULL;

  size_t len = (*size > 0) ? *size : strlen(buf);

  if (len <= 0) return NULL;

  unsigned char *outbuf = (unsigned char*)malloc((len/4)*3+3);

  if (!outbuf) return NULL;

  const char *ptr = buf;

  size_t p = 0;

  int wv, w1, w2, w3, w4;

  int tmpval[4];

  int tmpcnt = 0;

  do {

    while (ptr < buf+len && (*ptr == ' ' || *ptr == '\t' || *ptr == '\n' || *ptr == '\r')) {

      ptr++;

    }

    if (*ptr == '\0' || ptr >= buf+len) {

      break;

    }

    if ((wv = base64_table[(int)(unsigned char)*ptr++]) == -1) {

      continue;

    }

    tmpval[tmpcnt++] = wv;

    if (tmpcnt == 4) {

      tmpcnt = 0;

      w1 = tmpval[0];

      w2 = tmpval[1];

      w3 = tmpval[2];

      w4 = tmpval[3];

      if (w1 >= 0 && w2 >= 0) {

        outbuf[p++] = (unsigned char)(((w1 << 2) + (w2 >> 4)) & 0xFF);

      }

      if (w2 >= 0 && w3 >= 0) {

        outbuf[p++] = (unsigned char)(((w2 << 4) + (w3 >> 2)) & 0xFF);

      }

      if (w3 >= 0 && w4 >= 0) {

        outbuf[p++] = (unsigned char)(((w3 << 6) + w4) & 0xFF);

      }

    }

  } while (1);

  outbuf[p] = 0;

  *size = p;

  return outbuf;

}