How to Implement Base64 Decoding in C ?

Base64 Decode in C

Base64 is a widely used binary-to-text encoding scheme, employed in various applications, including data transmission and image storage. For convenience, many programming languages offer built-in Base64 encoding/decoding functionality. However, if you're working with C , you'll need to find a suitable library or implement your own code snippet.

A Modified Base64 Decoding Implementation

The following is a modified version of an existing Base64 decoding implementation in C :

Header File 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& encoded_string);

#endif

Source File 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) {
  ...  // Encoding implementation
  return ret;
}

std::vector<BYTE> base64_decode(std::string const& encoded_string) {
  ...  // Decoding implementation
  return ret;
}

Usage

To use the implementation, you can include the base64.h header and call the base64_decode function as follows:

std::string encodedData = "encoded_data_as_a_string";
std::vector<BYTE> decodedData = base64_decode(encodedData);

Additional Notes

• The BYTE type is an alias for unsigned char.
• The encoding and decoding functions operate on raw binary data and a string representation, respectively.
• The encoding function generates a string with a URL-safe Base64 representation.
• This snippet provides the necessary functionality for Base64 decoding in C , but please note that there are also other alternatives and libraries available that you may find more suitable for your specific needs.

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