Question

Is there a freely available Base64 decoding code snippet in C++?

Answer 1

See Encoding and decoding base 64 with C++.

Here is the implementation from that page:

/*    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 [e-mail]  */  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; }