Base64 decode snippet in C++

Question

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

Answer 1

Here's my modification of the implementation that was originally written by René Nyffenegger. And why have I modified it? Well, because it didn't seem appropriate to me that I should work with binary data stored within std::string object ;)

base64.h:

#ifndef _BASE64_H_ #define _BASE64_H_  #include <vector> #include <string> typedef unsigned char BYTE;  std::string base64_encode(BYTE const* buf, unsigned int bufLen); std::vector<BYTE> base64_decode(std::string const&);  #endif 

base64.cpp:

#include "base64.h" #include <iostream>  static const std::string base64_chars =              "ABCDEFGHIJKLMNOPQRSTUVWXYZ"              "abcdefghijklmnopqrstuvwxyz"              "0123456789+/";   static inline bool is_base64(BYTE c) {   return (isalnum(c) || (c == '+') || (c == '/')); }  std::string base64_encode(BYTE const* buf, unsigned int bufLen) {   std::string ret;   int i = 0;   int j = 0;   BYTE char_array_3[3];   BYTE char_array_4[4];    while (bufLen--) {     char_array_3[i++] = *(buf++);     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::vector<BYTE> base64_decode(std::string const& encoded_string) {   int in_len = encoded_string.size();   int i = 0;   int j = 0;   int in_ = 0;   BYTE char_array_4[4], char_array_3[3];   std::vector<BYTE> 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.push_back(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.push_back(char_array_3[j]);   }    return ret; } 

Here's the usage:

std::vector<BYTE> myData; ... std::string encodedData = base64_encode(&myData[0], myData.size()); std::vector<BYTE> decodedData = base64_decode(encodedData);