How Can I Efficiently Encode and Decode Base64 Data in C ?

Decoding Base64 in C : A Detailed Guide

In today's digital world, Base64 encoding is a widely used technique for representing binary data in a text-based format. It becomes necessary to decode this data back to its original form for further processing. Fortunately, there are effective C libraries available to assist you in both encoding and decoding Base64.

One such open-source and user-friendly library is presented below. This code snippet provides two essential functions: base64_encode() and base64_decode(). The encode function converts binary data into a Base64-encoded string, while the decode function performs the reverse operation, transforming the encoded string back into binary data.

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</byte></string></vector>

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_4[2] = ((char_array_3[1] & 0x0f) > 6);
      char_array_4[3] = char_array_3[2] & 0x3f;

      for(i = 0; (i ';

    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
    char_array_4[1] = ((char_array_3[0] & 0x03) > 4);
    char_array_4[2] = ((char_array_3[1] & 0x0f) > 6);
    char_array_4[3] = char_array_3[2] & 0x3f;

    for (j = 0; (j  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);
      char_array_3[1] = ((char_array_4[1] & 0xf) > 2);
      char_array_3[2] = ((char_array_4[2] & 0x3) >
4);
    char_array_3[1] = ((char_array_4[1] & 0xf) > 2);</byte></iostream>

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