base64开源库介绍及使用

骑猪看日落 2022-04-03 14:22 818阅读 0赞

网上有一些开源的base64编解码库的实现，下面介绍几个：

cppcodec是一个仅包括头文件的C++11库，用于编解码RFC 4648中指定的base64, base64url, base32, base32hex等，它的License为MIT，源码在[https://github.com/tplgy/cppcodec][https_github.com_tplgy_cppcodec] ,最新发布版本为v0.2，在windows下需要vs2015及以上才可以正常编译。

b64.c是一个C语言实现的base64编解码库，它的License为MIT，源码在[https://github.com/littlstar/b64.c][https_github.com_littlstar_b64.c]。

在[https://stackoverflow.com/questions/342409/how-do-i-base64-encode-decode-in-c][https_stackoverflow.com_questions_342409_how-do-i-base64-encode-decode-in-c]中给出了一个实现，并给出了一些base64开源库的性能测试结果。

关于base64的介绍可以参考：[https://blog.csdn.net/fengbingchun/article/details/85016088][https_blog.csdn.net_fengbingchun_article_details_85016088]

以下是两种base64开源库(b64.c和stackoverflow中给出的)实现的测试代码：

#include "funset.hpp"
    #include <stdio.h>
    #include <stdlib.h>
    #include <stdint.h>
    #include <string>
    #include <b64/b64.h>
    
    namespace {
    // reference: https://stackoverflow.com/questions/342409/how-do-i-base64-encode-decode-in-c
    static char encoding_table[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
    				'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    				'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
    				'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    				'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    				'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    				'w', 'x', 'y', 'z', '0', '1', '2', '3',
    				'4', '5', '6', '7', '8', '9', '+', '/' };
    static char *decoding_table = NULL;
    static int mod_table[] = { 0, 2, 1 };
    
    void build_decoding_table()
    {
    	decoding_table = (char*)malloc(256);
    
    	for (int i = 0; i < 64; i++)
    		decoding_table[(unsigned char)encoding_table[i]] = i;
    }
    
    char* base64_encode(const unsigned char *data, size_t input_length, size_t *output_length)
    {
    	*output_length = 4 * ((input_length + 2) / 3);
    
    	char *encoded_data = (char*)malloc(*output_length);
    	if (encoded_data == NULL) return NULL;
    
    	for (int i = 0, j = 0; i < input_length;) {
    		uint32_t octet_a = i < input_length ? (unsigned char)data[i++] : 0;
    		uint32_t octet_b = i < input_length ? (unsigned char)data[i++] : 0;
    		uint32_t octet_c = i < input_length ? (unsigned char)data[i++] : 0;
    
    		uint32_t triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;
    
    		encoded_data[j++] = encoding_table[(triple >> 3 * 6) & 0x3F];
    		encoded_data[j++] = encoding_table[(triple >> 2 * 6) & 0x3F];
    		encoded_data[j++] = encoding_table[(triple >> 1 * 6) & 0x3F];
    		encoded_data[j++] = encoding_table[(triple >> 0 * 6) & 0x3F];
    	}
    
    	for (int i = 0; i < mod_table[input_length % 3]; i++)
    		encoded_data[*output_length - 1 - i] = '=';
    
    	return encoded_data;
    }
    
    unsigned char* base64_decode(const char *data, size_t input_length, size_t *output_length)
    {
    	if (decoding_table == NULL) build_decoding_table();
    
    	if (input_length % 4 != 0) return NULL;
    
    	*output_length = input_length / 4 * 3;
    	if (data[input_length - 1] == '=') (*output_length)--;
    	if (data[input_length - 2] == '=') (*output_length)--;
    
    	unsigned char *decoded_data = (unsigned char*)malloc(*output_length);
    	if (decoded_data == NULL) return NULL;
    
    	for (int i = 0, j = 0; i < input_length;) {
    		uint32_t sextet_a = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
    		uint32_t sextet_b = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
    		uint32_t sextet_c = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
    		uint32_t sextet_d = data[i] == '=' ? 0 & i++ : decoding_table[data[i++]];
    
    		uint32_t triple = (sextet_a << 3 * 6)
    			+ (sextet_b << 2 * 6)
    			+ (sextet_c << 1 * 6)
    			+ (sextet_d << 0 * 6);
    
    		if (j < *output_length) decoded_data[j++] = (triple >> 2 * 8) & 0xFF;
    		if (j < *output_length) decoded_data[j++] = (triple >> 1 * 8) & 0xFF;
    		if (j < *output_length) decoded_data[j++] = (triple >> 0 * 8) & 0xFF;
    	}
    
    	return decoded_data;
    }
    
    void base64_cleanup()
    {
    	free(decoding_table);
    }
    
    } // namespace
    
    int test_b64_base64()
    {
    	std::string str = "北京ABC123+-*/&@!?0";
    	fprintf(stdout, "str source : %s\n", str.c_str());
    
    	char* str_en = b64_encode((const unsigned char*)str.c_str(), str.length());
    	fprintf(stdout, "str encode : %s\n", str_en);
    
    	std::string tmp(str_en);
    	//fprintf(stdout, "str_en length: %d\n", tmp.length());
    	unsigned char* str_de = b64_decode(tmp.c_str(), tmp.length());
    	fprintf(stdout, "str decode : %s\n", str_de);
    
    	free(str_en);
    	free(str_de);
    
    	size_t output_length_encode = 0;
    	char* str_en2 = base64_encode((const unsigned char*)str.c_str(), str.length(), &output_length_encode);
    	std::string tmp2(str_en2, output_length_encode);
    	fprintf(stdout, "str encode2: %s\n", tmp2.c_str());
    
    	size_t output_length_decode = 0;
    	//fprintf(stdout, "output_length_encode: %d, str_en2 length: %d\n", output_length_encode, tmp2.length());
    	unsigned char* str_de2 = base64_decode(str_en2, output_length_encode, &output_length_decode);
    	std::string tmp3((char*)str_de2, output_length_decode);
    	fprintf(stdout, "str decode2: %s\n", tmp3.c_str());
    
    	free(str_en2);
    	free(str_de2);
    	base64_cleanup();
    
    	return 0;
    }

执行结果如下：可见两种实现的base64编解码结果一致。

![20181222221608975.png][]

**GitHub**： [https://github.com/fengbingchun/OpenSSL\_Test][https_github.com_fengbingchun_OpenSSL_Test]

[https_github.com_tplgy_cppcodec]: https://github.com/tplgy/cppcodec
[https_github.com_littlstar_b64.c]: https://github.com/littlstar/b64.c
[https_stackoverflow.com_questions_342409_how-do-i-base64-encode-decode-in-c]: https://stackoverflow.com/questions/342409/how-do-i-base64-encode-decode-in-c
[https_blog.csdn.net_fengbingchun_article_details_85016088]: https://blog.csdn.net/fengbingchun/article/details/85016088
[20181222221608975.png]: /images/20220403/b6b6652ec15942fe855c268399c7fe61.png
[https_github.com_fengbingchun_OpenSSL_Test]: https://github.com/fengbingchun/OpenSSL_Test