/*
 *	UCW Library -- Base 64 Encoding & Decoding
 *
 *	(c) 2002, Robert Spalek <robert@ucw.cz>
 *	(c) 2018, Pavel Charvat <pchar@ucw.cz>
 *
 *	This software may be freely distributed and used according to the terms
 *	of the GNU Lesser General Public License.
 */

#undef LOCAL_DEBUG

#include <ucw/lib.h>
#include <ucw/base64.h>

const byte base64_enc_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const byte base64_dec_table[256] = {
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x3e, 0x80, 0x80, 0x80, 0x3f,
  0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x80, 0x80, 0x80, 0x40, 0x80, 0x80,
  0x80, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
  0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
  0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
  0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
};

uint base64_encode(byte *dest, const byte *src, uint len)
{
  const byte *ptr = src;
  const byte *end = src + len;
  byte *out = dest;

  /* keep going until we have less than 24 bits */
  if (end - ptr >= 3)
    for (const byte *x = end - 2; ptr < x; )
      {
	out[0] = base64_enc_table[ptr[0] >> 2];
	out[1] = base64_enc_table[((ptr[0] & 0x03) << 4) + (ptr[1] >> 4)];
	out[2] = base64_enc_table[((ptr[1] & 0x0f) << 2) + (ptr[2] >> 6)];
	out[3] = base64_enc_table[ptr[2] & 0x3f];
	out += 4;
	ptr += 3;
      }

  /* now deal with the tail end of things */
  if (ptr != end)
    {
      out[0] = base64_enc_table[ptr[0] >> 2];
      out[3] = BASE64_PADDING;
      if (end - ptr >= 2)
	{
	  out[1] = base64_enc_table[((ptr[0] & 0x03) << 4) + (ptr[1] >> 4)];
	  out[2] = base64_enc_table[(ptr[1] & 0x0f) << 2];
	}
      else
	{
	  out[1] = base64_enc_table[(ptr[0] & 0x03) << 4];
	  out[2] = BASE64_PADDING;
	}
      out += 4;
    }

  return out - dest;
}

uint base64_decode(byte *dest, const byte *src, uint len)
{
  const byte *ptr = src;
  const byte *end = src + len;
  byte *out = dest;
  while (1)
    {
      uint val, ch;
      do
	{
	  if (ptr == end || (ch = base64_dec_table[*ptr++]) == BASE64_DEC_PADDING)
	    goto end;
	}
      while (ch > BASE64_DEC_PADDING);
      val = ch;
      do
	{
	  if (ptr == end || (ch = base64_dec_table[*ptr++]) == BASE64_DEC_PADDING)
	    goto end; // Broken base64 encoding, we only have 6 bits
	}
      while (ch > BASE64_DEC_PADDING);
      val = (val << 6) | ch;
      do
	{
	  if (ptr == end || (ch = base64_dec_table[*ptr++]) == BASE64_DEC_PADDING)
	    {
	      out[0] = val >> 4;
	      out += 1;
	      goto end;
	    }
	}
      while (ch > BASE64_DEC_PADDING);
      val = (val << 6) | ch;
      do
	{
	  if (ptr == end || (ch = base64_dec_table[*ptr++]) == BASE64_DEC_PADDING)
	    {
	      out[0] = val >> 10;
	      out[1] = val >> 2;
	      out += 2;
	      goto end;
	    }
	}
      while (ch > BASE64_DEC_PADDING);
      val = (val << 6) | ch;
      out[0] = val >> 16;
      out[1] = val >> 8;
      out[2] = val;
      out += 3;
    }
end:
  return out - dest;
}