Encoding and decoding base64 with C++_copyright(c)2004-2008-优快云博客

本文介绍了一个Base64编码和解码的C++实现，包括完整的源代码和一个测试示例。该实现遵循标准Base64编码规则，并且提供了灵活的使用方式。

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The cpp file

base64.cpp

/* 

   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



*/



#include "base64.h"

#include <iostream>



static const std::string base64_chars = 

             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

             "abcdefghijklmnopqrstuvwxyz"

             "0123456789+/";





static inline bool is_base64(unsigned char c) {

  return (isalnum(c) || (c == '+') || (c == '/'));

}



std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len) {

  std::string ret;

  int i = 0;

  int j = 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] = (char_array_3[0] & 0xfc) >> 2;

      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);

      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);

      char_array_4[3] = char_array_3[2] & 0x3f;



      for(i = 0; (i <4) ; i++)

        ret += base64_chars[char_array_4[i]];

      i = 0;

    }

  }



  if (i)

  {

    for(j = i; j < 3; j++)

      char_array_3[j] = '/0';



    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;

    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);

    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);

    char_array_4[3] = char_array_3[2] & 0x3f;



    for (j = 0; (j < i + 1); j++)

      ret += base64_chars[char_array_4[j]];



    while((i++ < 3))

      ret += '=';



  }



  return ret;



}



std::string base64_decode(std::string const& encoded_string) {

  int in_len = encoded_string.size();

  int i = 0;

  int j = 0;

  int 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] = base64_chars.find(char_array_4[i]);



      char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);

      char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);

      char_array_3[2] = ((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 (j = i; j <4; j++)

      char_array_4[j] = 0;



    for (j = 0; j <4; j++)

      char_array_4[j] = base64_chars.find(char_array_4[j]);



    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);

    char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);

    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];



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

  }



  return ret;

}

The header file

base64.h

#include <string>



std::string base64_encode(unsigned char const* , unsigned int len);

std::string base64_decode(std::string const& s);

The test file

#include "base64.h"

#include <iostream>



int main() {

  const std::string s = "ADP GmbH/nAnalyse Design & Programmierung/nGesellschaft mit beschränkter Haftung" ;



  std::string encoded = base64_encode(reinterpret_cast<const unsigned char*>(s.c_str()), s.length());

  std::string decoded = base64_decode(encoded);



  std::cout << "encoded: " << encoded << std::endl;

  std::cout << "decoded: " << decoded << std::endl;



  return 0;

}