/*=========================================================================

  Program: GDCM (Grassroots DICOM). A DICOM library

  Copyright (c) 2006-2011 Mathieu Malaterre
  All rights reserved.
  See Copyright.txt or http://gdcm.sourceforge.net/Copyright.html for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
#include "gdcmBase64.h"
#include <cstring> // memcpy
#include <iostream>

namespace gdcm
{
/* 
   base64.cpp and base64.h

   Copyright (C) 2004-2008 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original source code.

   3. This notice may not be removed or altered from any source distribution.

   René Nyffenegger rene.nyffenegger@adp-gmbh.ch

*/


static const std::string base64_chars = 
             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
             "abcdefghijklmnopqrstuvwxyz"
             "0123456789+/";


static inline bool is_base64(unsigned char c) {
  return (isalnum(c) || (c == '+') || (c == '/'));
}

static std::string base64_encode(unsigned char const* bytes_to_encode, size_t in_len)
{
  std::string ret;
  size_t i = 0;
  unsigned char char_array_3[3];
  unsigned char char_array_4[4];

  while (in_len--) {
    char_array_3[i++] = *(bytes_to_encode++);
    if (i == 3) {
      char_array_4[0] = (unsigned char)((char_array_3[0] & 0xfc) >> 2);
      char_array_4[1] = (unsigned char)(((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4));
      char_array_4[2] = (unsigned char)(((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6));
      char_array_4[3] = (unsigned char)(char_array_3[2] & 0x3f);

      for(i = 0; i < 4; i++)
        ret += base64_chars[char_array_4[i]];
      i = 0;
    }
  }

  if (i)
    {
    for(size_t j = i; j < 3; j++)
      char_array_3[j] = '\0';

    char_array_4[0] = (unsigned char)((char_array_3[0] & 0xfc) >> 2);
    char_array_4[1] = (unsigned char)(((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4));
    char_array_4[2] = (unsigned char)(((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6));
    char_array_4[3] = (unsigned char)(char_array_3[2] & 0x3f);

    for (size_t j = 0; j < i + 1; j++)
      ret += base64_chars[char_array_4[j]];

    while((i++ < 3))
      ret += '=';

    }

  return ret;
}

static std::string base64_decode(std::string const& encoded_string)
{
  size_t in_len = encoded_string.size();
  size_t i = 0;
  size_t in_ = 0;
  unsigned char char_array_4[4], char_array_3[3];
  std::string ret;

  while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) {
    char_array_4[i++] = encoded_string[in_]; in_++;
    if (i ==4) {
      for (i = 0; i <4; i++)
        char_array_4[i] = (unsigned char)base64_chars.find(char_array_4[i]);

      char_array_3[0] = (unsigned char)((char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4));
      char_array_3[1] = (unsigned char)(((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2));
      char_array_3[2] = (unsigned char)(((char_array_4[2] & 0x3) << 6) + char_array_4[3]);

      for (i = 0; (i < 3); i++)
        ret += char_array_3[i];
      i = 0;
    }
  }

  if (i) {
    for (size_t j = i; j <4; j++)
      char_array_4[j] = 0;

    for (size_t j = 0; j <4; j++)
      char_array_4[j] = (unsigned char)base64_chars.find(char_array_4[j]);

    char_array_3[0] = (unsigned char)((char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4));
    char_array_3[1] = (unsigned char)(((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2));
    char_array_3[2] = (unsigned char)(((char_array_4[2] & 0x3) << 6) + char_array_4[3]);

    for (size_t j = 0; (j < i - 1); j++)
      ret += char_array_3[j];
  }

  return ret;
}

size_t Base64::GetEncodeLength(const char *src, size_t slen )
{
  std::string ret = base64_encode((const unsigned char*)src, slen);
  return ret.size();
}

size_t Base64::Encode( char *dst, size_t dlen, const char *src, size_t slen )
{
  const std::string & ret = base64_encode((const unsigned char*)src, slen);
  if( ret.size() > dlen )
    return 0;
  memcpy( dst, ret.c_str(), ret.size() );
  return ret.size();
}

size_t Base64::GetDecodeLength( const char *src, size_t slen )
{
  const std::string & ret = base64_decode( std::string( src, slen) );
  return ret.size();
}

size_t Base64::Decode( char *dst, size_t dlen, const char *src, size_t slen )
{
  const std::string & ret = base64_decode( std::string( src, slen) );
  if( ret.size() > dlen )
    return 0;
  memcpy( dst, ret.c_str(), ret.size() );
  return ret.size();
}

} // end namespace gdcm
