/*
   * Copyright (C) 2014 Hochschule für Angewandte Wissenschaften Hamburg (HAW)
   * Copyright (C) 2014 Martin Landsmann <Martin.Landsmann@HAW-Hamburg.de>
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @ingroup base64
   * @{
   * @file
   * @brief   Functions to encode and decode base64
   *
   * @author  Martin Landsmann <Martin.Landsmann@HAW-Hamburg.de>
   * @}
   *
   */
  
  #include "base64.h"
  
  #define BASE64_CAPITAL_UPPER_BOUND     (25)     /**< base64 'Z'           */
  #define BASE64_SMALL_UPPER_BOUND       (51)     /**< base64 'z'           */
  #define BASE64_NUMBER_UPPER_BOUND      (61)     /**< base64 '9'           */
  #define BASE64_PLUS                    (62)     /**< base64 '+'           */
  #define BASE64_SLASH                   (63)     /**< base64 '/'           */
  #define BASE64_EQUALS                  (0xFE)   /**< no base64 symbol '=' */
  #define BASE64_NOT_DEFINED             (0xFF)   /**< no base64 symbol     */
  
  /*
   * returns the corresponding ascii symbol value for the given base64 code
   */
  static char getsymbol(unsigned char code)
  {
      if (code == BASE64_SLASH) {
          return '/';
      }
  
      if (code == BASE64_PLUS) {
          return '+';
      }
  
      if (code <= BASE64_CAPITAL_UPPER_BOUND) {
          return (code + 'A');
      }
  
      if (code <= BASE64_SMALL_UPPER_BOUND) {
          return (code + ('z' - BASE64_SMALL_UPPER_BOUND));
      }
  
      if (code <= BASE64_NUMBER_UPPER_BOUND) {
          return (code + ('9' - BASE64_NUMBER_UPPER_BOUND));
      }
  
      return (char)BASE64_NOT_DEFINED;
  }
  
  int base64_encode(unsigned char *data_in, size_t data_in_size, \
                    unsigned char *base64_out, size_t *base64_out_size)
  {
      size_t required_size = 4 * ((data_in_size + 2) / 3);
  
      if (data_in == NULL) {
          return BASE64_ERROR_DATA_IN;
      }
  
      if (data_in_size < 1) {
          return BASE64_ERROR_DATA_IN_SIZE;
      }
  
      if (*base64_out_size < required_size) {
          *base64_out_size = required_size;
          return BASE64_ERROR_BUFFER_OUT_SIZE;
      }
  
      if (base64_out == NULL) {
          return BASE64_ERROR_BUFFER_OUT;
      }
  
      int iterate_base64_buffer = 0;
      unsigned char nNum = 0;
      int nLst = 0;
      int njump = 0;
  
      for (int i = 0; i < (int)(data_in_size); ++i) {
          unsigned char tmpval;
          njump++;
          tmpval = *(data_in + i);
  
          nNum = (tmpval >> (2 * njump));
  
          if (njump == 4) {
              nNum = nLst << (8 - 2 * njump);
              njump = 0;
              nLst = 0;
              --i;
          }
          else {
              nNum += nLst << (8 - 2 * njump);
              nLst =  tmpval & ((1 << njump * 2) - 1);
          }
  
          base64_out[iterate_base64_buffer++] = getsymbol(nNum);
      }
  
      /* The last character is not finished yet */
      njump++;
  
      nNum = nLst << (8 - 2 * njump);
      base64_out[iterate_base64_buffer++] = getsymbol(nNum);
  
      /* if required we append '=' for the required dividability */
      while (iterate_base64_buffer % 4) {
          base64_out[iterate_base64_buffer++] = '=';
      }
  
      *base64_out_size = iterate_base64_buffer;
  
      return BASE64_SUCCESS;
  }
  
  /*
   *  returns the corresponding base64 code for the given ascii symbol
   */
  static int getcode(char symbol)
  {
      if (symbol == '/') {
          return BASE64_SLASH;
      }
  
      if (symbol == '+') {
          return BASE64_PLUS;
      }
  
      if (symbol == '=') {
          /* indicates a padded base64 end */
          return BASE64_EQUALS;
      }
  
      if (symbol < '0') {
          /* indicates that the given symbol is not base64 and should be ignored */
          return BASE64_NOT_DEFINED;
      }
  
      if (symbol <= '9' && symbol >= '0') {
          return (symbol + (BASE64_NUMBER_UPPER_BOUND - '9'));
      }
  
      if (symbol <= 'Z' && symbol >= 'A') {
          return (symbol - 'A');
      }
  
      if (symbol <= 'z' && symbol >= 'a') {
          return (symbol + (BASE64_SMALL_UPPER_BOUND - 'z'));
      }
  
      /* indicates that the given symbol is not base64 and should be ignored */
      return BASE64_NOT_DEFINED;
  }
  
  int base64_decode(unsigned char *base64_in, size_t base64_in_size, \
                    unsigned char *data_out, size_t *data_out_size)
  {
      size_t required_size = ((base64_in_size / 4) * 3);
  
      if (base64_in == NULL) {
          return BASE64_ERROR_DATA_IN;
      }
  
      if (base64_in_size < 4) {
          return BASE64_ERROR_DATA_IN_SIZE;
      }
  
      if (*data_out_size < required_size) {
          *data_out_size = required_size;
          return BASE64_ERROR_BUFFER_OUT_SIZE;
      }
  
      if (data_out == NULL) {
          return BASE64_ERROR_BUFFER_OUT;
      }
  
      int iterate_data_buffer = 0;
      unsigned char nNum = 0;
      int nLst = getcode(base64_in[0]) << 2;
      int code = 0;
  
      int mask = 2;
  
      for (int i = 1; i < (int)(base64_in_size); i++) {
          code = getcode(base64_in[i]);
  
          if (code == BASE64_NOT_DEFINED || code == BASE64_EQUALS) {
              continue;
          }
  
          int nm = (0xFF << (2 * mask));
  
          nNum = nLst + ((code & (0xFF & nm)) >> (2 * mask));
          nLst = (code & (0xFF & ~nm)) << (8 - (2 * mask));
  
          (mask != 3) ? data_out[iterate_data_buffer++] = nNum : nNum;
          (mask == 0) ? mask = 3 : mask--;
      }
  
      if (code == BASE64_EQUALS) {
          /* add the last character to the data_out buffer */
          data_out[iterate_data_buffer] = nNum;
      }
  
      *data_out_size = iterate_data_buffer;
      return BASE64_SUCCESS;
  }