/*
 * Base64 encode/decode functions used in sxmp
 * openssl stuff wasn't used to avoid additional memleaks and allocation,
 * deallocation of BIO and to avoid dependency, since not only openssl
 * might be in use
 *
 * (c) Alexander Vdolainen 2016 <avdolainen@zoho.com>
 *
 * libsxmp 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.
 *
 * libsxmp 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 program.  If not, see <http://www.gnu.org/licenses/>.";
 */

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

#include <sxt/base64.h>

static const char b64[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static inline void encodeblock(unsigned char *in, unsigned char *out, int len)
{
  out[0] = (unsigned char) b64[ (int)(in[0] >> 2) ];
  out[1] = (unsigned char) b64[ (int)(((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4)) ];
  out[2] = (unsigned char) (len > 1 ? b64[ (int)(((in[1] & 0x0f) << 2) | ((in[2] & 0xc0) >> 6)) ] : '=');
  out[3] = (unsigned char) (len > 2 ? b64[ (int)(in[2] & 0x3f) ] : '=');
}

static inline char __block(char b)
{
  const char *j = strchr(b64, b);

  if(j) return j - b64;
  else return 0;
}

static inline void decodeblock(unsigned char *in, unsigned char *out)
{
  char a = __block(in[0]);
  char b = __block(in[1]);
  char c = __block(in[2]);
  char d = __block(in[3]);

  out[0] = (unsigned char) (a << 2 | b >> 4);
  out[1] = (unsigned char) (b << 4 | c >> 2);
  out[2] = (unsigned char) (((c << 6) & 0xc0) | d);
}

size_t sxt_rawlen2b64len(size_t raw_length)
{
  return (size_t)(((4 * raw_length / 3) + 3) & ~3);
}

size_t sxt_b64encode_in(const char *data, char *bdata, size_t data_len)
{
  size_t bdata_len = 0, c = 0, n = 0;
  int len = 0, nil = 0, i;
  unsigned char ib[4];

  if(!bdata) return -1;
  if(!data || !data_len) return -1;
  else bdata_len = sxt_rawlen2b64len(data_len);

  while(n != bdata_len) {
    if((c + 3) <= data_len) {
      len = 3;
      encodeblock((unsigned char *)data + c, (unsigned char *)bdata + n, len);
      n += 4; c += 3;
    } else {
      nil = (c + 3) - data_len;
      len = 0;
      for(i = 0; i < 3; i++) {
        if(i < nil + 1) {
          ib[i] = *((unsigned char *)data + (c + i));
          len++;
        } else ib[i] = (unsigned char)0;
      }
      encodeblock(ib, (unsigned char *)bdata + n, len);
      break;
    }
  }

  return bdata_len;
}

char *sxt_b64encode(const char *data, size_t data_len)
{
  char *bdata = NULL;
  size_t bdata_len = 0;

  if(!data || !data_len) return NULL;
  else bdata_len = sxt_rawlen2b64len(data_len);

  if(!(bdata = malloc(bdata_len))) return NULL;

  sxt_b64encode_in(data, bdata, data_len);

  return bdata;
}

size_t sxt_b64decode_in(const char *idata, size_t idata_len, char *data, size_t data_len)
{
  size_t enc = 0, dec = 0;

  if(!idata || !idata_len) return -1;
  if(!data || !data_len) return -1;

  for(enc = 0; enc != idata_len; enc += 4) {
    if(dec >= data_len) return dec;
    decodeblock((unsigned char *)idata + enc, (unsigned char *)data + dec);
    dec += 3;
  }

  return dec;
}