我在unsigned char变量中有二进制数据。 我需要将它们转换为c中的PEM base64。 我查看了openssl库，但我找不到任何功能。 有没有人有任何想法？
答案 0 :(得分：101)
这是我正在使用的那个：
#include <stdint.h>
#include <stdlib.h>
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};
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 = 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 = 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 build_decoding_table() {
decoding_table = malloc(256);
for (int i = 0; i < 64; i++)
decoding_table[(unsigned char) encoding_table[i]] = i;
}
void base64_cleanup() {
free(decoding_table);
}
请记住，这在解码时不会进行任何错误检查 - 非基本64位编码数据将被处理。
答案 1 :(得分：41)
我知道这个问题很老了，但我对所提供的解决方案数量感到困惑 - 他们每个人都声称自己更快更好。我在github上组合了一个项目来比较base64编码器和解码器：https://github.com/gaspardpetit/base64/
此时，我并不局限于C算法 - 如果一个实现在C ++中表现良好，它可以很容易地向后移植到C.还使用Visual Studio 2015进行测试。如果有人想用结果更新这个答案来自clang / gcc，是我的客人。
最快的编码员： 我找到的两个最快的编码器实现是http://web.mit.edu/freebsd/head/contrib/wpa/src/utils/base64.c的Jouni Malinen和https://opensource.apple.com/source/QuickTimeStreamingServer/QuickTimeStreamingServer-452/CommonUtilitiesLib/base64.c的Apache。
以下是使用我到目前为止测试的不同算法编码32K数据的时间（以微秒为单位）：
jounimalinen 25.1544
apache 25.5309
NibbleAndAHalf 38.4165
internetsoftwareconsortium 48.2879
polfosol 48.7955
wikibooks_org_c 51.9659
gnome 74.8188
elegantdice 118.899
libb64 120.601
manuelmartinez 120.801
arduino 126.262
daedalusalpha 126.473
CppCodec 151.866
wikibooks_org_cpp 343.2
adp_gmbh 381.523
LihO 406.693
libcurl 3246.39
user152949 4828.21
（RenéNyffenegger的解决方案，在此问题的另一个答案中记入，在此列为adp_gmbh）。
这是来自Jouni Malinen的一个我稍微修改后返回一个std :: string：
/*
* Base64 encoding/decoding (RFC1341)
* Copyright (c) 2005-2011, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
// 2016-12-12 - Gaspard Petit : Slightly modified to return a std::string
// instead of a buffer allocated with malloc.
#include <string>
static const unsigned char base64_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/**
* base64_encode - Base64 encode
* @src: Data to be encoded
* @len: Length of the data to be encoded
* @out_len: Pointer to output length variable, or %NULL if not used
* Returns: Allocated buffer of out_len bytes of encoded data,
* or empty string on failure
*/
std::string base64_encode(const unsigned char *src, size_t len)
{
unsigned char *out, *pos;
const unsigned char *end, *in;
size_t olen;
olen = 4*((len + 2) / 3); /* 3-byte blocks to 4-byte */
if (olen < len)
return std::string(); /* integer overflow */
std::string outStr;
outStr.resize(olen);
out = (unsigned char*)&outStr[0];
end = src + len;
in = src;
pos = out;
while (end - in >= 3) {
*pos++ = base64_table[in[0] >> 2];
*pos++ = base64_table[((in[0] & 0x03) << 4) | (in[1] >> 4)];
*pos++ = base64_table[((in[1] & 0x0f) << 2) | (in[2] >> 6)];
*pos++ = base64_table[in[2] & 0x3f];
in += 3;
}
if (end - in) {
*pos++ = base64_table[in[0] >> 2];
if (end - in == 1) {
*pos++ = base64_table[(in[0] & 0x03) << 4];
*pos++ = '=';
}
else {
*pos++ = base64_table[((in[0] & 0x03) << 4) |
(in[1] >> 4)];
*pos++ = base64_table[(in[1] & 0x0f) << 2];
}
*pos++ = '=';
}
return outStr;
}
最快的解码器：这是解码结果，我必须承认我有点惊讶：
polfosol 45.2335
wikibooks_org_c 74.7347
apache 77.1438
libb64 100.332
gnome 114.511
manuelmartinez 126.579
elegantdice 138.514
daedalusalpha 151.561
jounimalinen 206.163
arduino 335.95
wikibooks_org_cpp 350.437
CppCodec 526.187
internetsoftwareconsortium 862.833
libcurl 1280.27
LihO 1852.4
adp_gmbh 1934.43
user152949 5332.87
来自base64 decode snippet in c++的Polfosol片段速度最快，差不多是2倍。
以下是为了完整性而编写的代码：
static const int B64index[256] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 62, 63, 62, 62, 63, 52, 53, 54, 55,
56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0,
0, 0, 0, 63, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
std::string b64decode(const void* data, const size_t len)
{
unsigned char* p = (unsigned char*)data;
int pad = len > 0 && (len % 4 || p[len - 1] == '=');
const size_t L = ((len + 3) / 4 - pad) * 4;
std::string str(L / 4 * 3 + pad, '\0');
for (size_t i = 0, j = 0; i < L; i += 4)
{
int n = B64index[p[i]] << 18 | B64index[p[i + 1]] << 12 | B64index[p[i + 2]] << 6 | B64index[p[i + 3]];
str[j++] = n >> 16;
str[j++] = n >> 8 & 0xFF;
str[j++] = n & 0xFF;
}
if (pad)
{
int n = B64index[p[L]] << 18 | B64index[p[L + 1]] << 12;
str[str.size() - 1] = n >> 16;
if (len > L + 2 && p[L + 2] != '=')
{
n |= B64index[p[L + 2]] << 6;
str.push_back(n >> 8 & 0xFF);
}
}
return str;
}
答案 2 :(得分：30)
但你也可以在openssl中执行它（openssl enc命令吗....），看看BIO_f_base64()函数
答案 3 :(得分：16)
libb64同时包含C和C ++ API。它是轻量级的，也许是最快的公开实现。它也是一个专用的独立base64编码库，如果你不需要使用更大的库（如OpenSSL或glib）所带来的所有其他东西，这可能会很好。
答案 4 :(得分：15)
这是我使用OpenSSL的解决方案。
/* A BASE-64 ENCODER AND DECODER USING OPENSSL */
#include <openssl/pem.h>
#include <string.h> //Only needed for strlen().
char *base64encode (const void *b64_encode_this, int encode_this_many_bytes){
BIO *b64_bio, *mem_bio; //Declares two OpenSSL BIOs: a base64 filter and a memory BIO.
BUF_MEM *mem_bio_mem_ptr; //Pointer to a "memory BIO" structure holding our base64 data.
b64_bio = BIO_new(BIO_f_base64()); //Initialize our base64 filter BIO.
mem_bio = BIO_new(BIO_s_mem()); //Initialize our memory sink BIO.
BIO_push(b64_bio, mem_bio); //Link the BIOs by creating a filter-sink BIO chain.
BIO_set_flags(b64_bio, BIO_FLAGS_BASE64_NO_NL); //No newlines every 64 characters or less.
BIO_write(b64_bio, b64_encode_this, encode_this_many_bytes); //Records base64 encoded data.
BIO_flush(b64_bio); //Flush data. Necessary for b64 encoding, because of pad characters.
BIO_get_mem_ptr(mem_bio, &mem_bio_mem_ptr); //Store address of mem_bio's memory structure.
BIO_set_close(mem_bio, BIO_NOCLOSE); //Permit access to mem_ptr after BIOs are destroyed.
BIO_free_all(b64_bio); //Destroys all BIOs in chain, starting with b64 (i.e. the 1st one).
BUF_MEM_grow(mem_bio_mem_ptr, (*mem_bio_mem_ptr).length + 1); //Makes space for end null.
(*mem_bio_mem_ptr).data[(*mem_bio_mem_ptr).length] = '\0'; //Adds null-terminator to tail.
return (*mem_bio_mem_ptr).data; //Returns base-64 encoded data. (See: "buf_mem_st" struct).
}
char *base64decode (const void *b64_decode_this, int decode_this_many_bytes){
BIO *b64_bio, *mem_bio; //Declares two OpenSSL BIOs: a base64 filter and a memory BIO.
char *base64_decoded = calloc( (decode_this_many_bytes*3)/4+1, sizeof(char) ); //+1 = null.
b64_bio = BIO_new(BIO_f_base64()); //Initialize our base64 filter BIO.
mem_bio = BIO_new(BIO_s_mem()); //Initialize our memory source BIO.
BIO_write(mem_bio, b64_decode_this, decode_this_many_bytes); //Base64 data saved in source.
BIO_push(b64_bio, mem_bio); //Link the BIOs by creating a filter-source BIO chain.
BIO_set_flags(b64_bio, BIO_FLAGS_BASE64_NO_NL); //Don't require trailing newlines.
int decoded_byte_index = 0; //Index where the next base64_decoded byte should be written.
while ( 0 < BIO_read(b64_bio, base64_decoded+decoded_byte_index, 1) ){ //Read byte-by-byte.
decoded_byte_index++; //Increment the index until read of BIO decoded data is complete.
} //Once we're done reading decoded data, BIO_read returns -1 even though there's no error.
BIO_free_all(b64_bio); //Destroys all BIOs in chain, starting with b64 (i.e. the 1st one).
return base64_decoded; //Returns base-64 decoded data with trailing null terminator.
}
/*Here's one way to base64 encode/decode using the base64encode() and base64decode functions.*/
int main(void){
char data_to_encode[] = "Base64 encode this string!"; //The string we will base-64 encode.
int bytes_to_encode = strlen(data_to_encode); //Number of bytes in string to base64 encode.
char *base64_encoded = base64encode(data_to_encode, bytes_to_encode); //Base-64 encoding.
int bytes_to_decode = strlen(base64_encoded); //Number of bytes in string to base64 decode.
char *base64_decoded = base64decode(base64_encoded, bytes_to_decode); //Base-64 decoding.
printf("Original character string is: %s\n", data_to_encode); //Prints our initial string.
printf("Base-64 encoded string is: %s\n", base64_encoded); //Prints base64 encoded string.
printf("Base-64 decoded string is: %s\n", base64_decoded); //Prints base64 decoded string.
free(base64_encoded); //Frees up the memory holding our base64 encoded data.
free(base64_decoded); //Frees up the memory holding our base64 decoded data.
}
答案 5 :(得分：15)
glib具有base64编码功能：https://developer.gnome.org/glib/stable/glib-Base64-Encoding.html
答案 6 :(得分：14)
我需要 std :: string 的 C ++ 实现。没有一个答案满足我的需求，我需要简单的双功能解码编码和解码，但我懒得编写自己的代码，所以我发现了这个：
http://www.adp-gmbh.ch/cpp/common/base64.html
代码的归功于RenéNyffenegger。
如果网站出现故障，请输入以下代码：
<强> base64.cpp
/*
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 rene.nyffenegger@adp-gmbh.ch
*/
#include "base64.h"
#include <iostream>
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;
}
<强> base64.h
#include <string>
std::string base64_encode(unsigned char const* , unsigned int len);
std::string base64_decode(std::string const& s);
<强>用法
const std::string s = "test";
std::string encoded = base64_encode(reinterpret_cast<const unsigned char*>(s.c_str()), s.length());
std::string decoded = base64_decode(encoded);
答案 7 :(得分：13)
GNU coreutils在lib / base64中有它。它有点膨胀，但处理像EBCDIC这样的东西。您也可以自己玩，例如，
char base64_digit (n) unsigned n; {
if (n < 10) return n - '0';
else if (n < 10 + 26) return n - 'a';
else if (n < 10 + 26 + 26) return n - 'A';
else assert(0);
return 0;
}
unsigned char base64_decode_digit(char c) {
switch (c) {
case '=' : return 62;
case '.' : return 63;
default :
if (isdigit(c)) return c - '0';
else if (islower(c)) return c - 'a' + 10;
else if (isupper(c)) return c - 'A' + 10 + 26;
else assert(0);
}
return 0xff;
}
unsigned base64_decode(char *s) {
char *p;
unsigned n = 0;
for (p = s; *p; p++)
n = 64 * n + base64_decode_digit(*p);
return n;
}
通过这些礼物你们所有人都知道你们不应该把“自己玩耍”与“实施标准”混为一谈。 Yeesh。
答案 8 :(得分：8)
这是我多年来一直使用的解码器......
static const char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const int BASE64_INPUT_SIZE = 57;
BOOL isbase64(char c)
{
return c && strchr(table, c) != NULL;
}
inline char value(char c)
{
const char *p = strchr(table, c);
if(p) {
return p-table;
} else {
return 0;
}
}
int UnBase64(unsigned char *dest, const unsigned char *src, int srclen)
{
*dest = 0;
if(*src == 0)
{
return 0;
}
unsigned char *p = dest;
do
{
char a = value(src[0]);
char b = value(src[1]);
char c = value(src[2]);
char d = value(src[3]);
*p++ = (a << 2) | (b >> 4);
*p++ = (b << 4) | (c >> 2);
*p++ = (c << 6) | d;
if(!isbase64(src[1]))
{
p -= 2;
break;
}
else if(!isbase64(src[2]))
{
p -= 2;
break;
}
else if(!isbase64(src[3]))
{
p--;
break;
}
src += 4;
while(*src && (*src == 13 || *src == 10)) src++;
}
while(srclen-= 4);
*p = 0;
return p-dest;
}
答案 9 :(得分：4)
我写了一个用于C ++的，它非常快，适用于流，免费和开源：
https://tmplusplus.svn.sourceforge.net/svnroot/tmplusplus/trunk/src/
如果符合您的目的，请随意使用。
修改：按要求内联添加代码。
通过使用查找表进行编码和解码来提高性能。 _UINT8在大多数操作系统上都是unsigned char。
/** Static Base64 character encoding lookup table */
const char CBase64::encodeCharacterTable[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/** Static Base64 character decoding lookup table */
const char CBase64::decodeCharacterTable[256] = {
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
,-1,62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-1,-1,-1,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21
,22,23,24,25,-1,-1,-1,-1,-1,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1};
/*!
\brief Encodes binary data to base 64 character data
\param in The data to encode
\param out The encoded data as characters
*/
void CBase64::Encode(std::istream &in, std::ostringstream &out)
{
char buff1[3];
char buff2[4];
_UINT8 i=0, j;
while(in.readsome(&buff1[i++], 1))
if (i==3)
{
out << encodeCharacterTable[(buff1[0] & 0xfc) >> 2];
out << encodeCharacterTable[((buff1[0] & 0x03) << 4) + ((buff1[1] & 0xf0) >> 4)];
out << encodeCharacterTable[((buff1[1] & 0x0f) << 2) + ((buff1[2] & 0xc0) >> 6)];
out << encodeCharacterTable[buff1[2] & 0x3f];
i=0;
}
if (--i)
{
for(j=i;j<3;j++) buff1[j] = '\0';
buff2[0] = (buff1[0] & 0xfc) >> 2;
buff2[1] = ((buff1[0] & 0x03) << 4) + ((buff1[1] & 0xf0) >> 4);
buff2[2] = ((buff1[1] & 0x0f) << 2) + ((buff1[2] & 0xc0) >> 6);
buff2[3] = buff1[2] & 0x3f;
for (j=0;j<(i+1);j++) out << encodeCharacterTable[buff2[j]];
while(i++<3) out << '=';
}
}
/*!
\brief Decodes base 64 character data to binary data
\param in The character data to decode
\param out The decoded data
*/
void CBase64::Decode(std::istringstream &in, std::ostream &out)
{
char buff1[4];
char buff2[4];
_UINT8 i=0, j;
while(in.readsome(&buff2[i], 1) && buff2[i] != '=')
{
if (++i==4)
{
for (i=0;i!=4;i++)
buff2[i] = decodeCharacterTable[buff2[i]];
out << (char)((buff2[0] << 2) + ((buff2[1] & 0x30) >> 4));
out << (char)(((buff2[1] & 0xf) << 4) + ((buff2[2] & 0x3c) >> 2));
out << (char)(((buff2[2] & 0x3) << 6) + buff2[3]);
i=0;
}
}
if (i)
{
for (j=i;j<4;j++) buff2[j] = '\0';
for (j=0;j<4;j++) buff2[j] = decodeCharacterTable[buff2[j]];
buff1[0] = (buff2[0] << 2) + ((buff2[1] & 0x30) >> 4);
buff1[1] = ((buff2[1] & 0xf) << 4) + ((buff2[2] & 0x3c) >> 2);
buff1[2] = ((buff2[2] & 0x3) << 6) + buff2[3];
for (j=0;j<(i-1); j++) out << (char)buff1[j];
}
}
答案 10 :(得分：4)
如果人们需要c ++解决方案，我将这个OpenSSL解决方案放在一起（用于编码和解码）。您需要链接“加密”库（即OpenSSL）。已经使用valgrind检查了这是否泄漏（尽管你可以添加一些额外的错误检查代码以使它更好一点 - 我知道至少写函数应检查返回值）。
#include <openssl/bio.h>
#include <openssl/evp.h>
#include <stdlib.h>
string base64_encode( const string &str ){
BIO *base64_filter = BIO_new( BIO_f_base64() );
BIO_set_flags( base64_filter, BIO_FLAGS_BASE64_NO_NL );
BIO *bio = BIO_new( BIO_s_mem() );
BIO_set_flags( bio, BIO_FLAGS_BASE64_NO_NL );
bio = BIO_push( base64_filter, bio );
BIO_write( bio, str.c_str(), str.length() );
BIO_flush( bio );
char *new_data;
long bytes_written = BIO_get_mem_data( bio, &new_data );
string result( new_data, bytes_written );
BIO_free_all( bio );
return result;
}
string base64_decode( const string &str ){
BIO *bio, *base64_filter, *bio_out;
char inbuf[512];
int inlen;
base64_filter = BIO_new( BIO_f_base64() );
BIO_set_flags( base64_filter, BIO_FLAGS_BASE64_NO_NL );
bio = BIO_new_mem_buf( (void*)str.c_str(), str.length() );
bio = BIO_push( base64_filter, bio );
bio_out = BIO_new( BIO_s_mem() );
while( (inlen = BIO_read(bio, inbuf, 512)) > 0 ){
BIO_write( bio_out, inbuf, inlen );
}
BIO_flush( bio_out );
char *new_data;
long bytes_written = BIO_get_mem_data( bio_out, &new_data );
string result( new_data, bytes_written );
BIO_free_all( bio );
BIO_free_all( bio_out );
return result;
}
答案 11 :(得分：2)
来自ryyst（获得最多选票）的代码的小改进是不使用动态分配的解码表，而是使用静态const预计算表。这消除了指针的使用和表的初始化，并且如果忘记用base64_cleanup（）来清理解码表（顺便说一句，在base64_cleanup（）中，在调用free（decoding_table）之后，也可以避免内存泄漏） decoding_table = NULL，否则在base64_cleanup（）之后意外调用base64_decode会崩溃或导致未确定的行为）。另一个解决方案可能是使用std :: unique_ptr ...但是我很满意只在堆栈上使用const char [256]并避免全部使用指针 - 代码看起来更清晰，更短。
解码表计算如下：
const 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', '+', '/' };
unsigned char decoding_table[256];
for (int i = 0; i < 256; i++)
decoding_table[i] = '\0';
for (int i = 0; i < 64; i++)
decoding_table[(unsigned char)encoding_table[i]] = i;
for (int i = 0; i < 256; i++)
cout << "0x" << (int(decoding_table[i]) < 16 ? "0" : "") << hex << int(decoding_table[i]) << (i != 255 ? "," : "") << ((i+1) % 16 == 0 ? '\n' : '\0');
cin.ignore();
我正在使用的修改后的代码是：
static const 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 const unsigned char decoding_table[256] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3e, 0x00, 0x00, 0x00, 0x3f,
0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
char* base64_encode(const unsigned char *data, size_t input_length, size_t &output_length) {
const int mod_table[] = { 0, 2, 1 };
output_length = 4 * ((input_length + 2) / 3);
char *encoded_data = (char*)malloc(output_length);
if (encoded_data == nullptr)
return nullptr;
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 (input_length % 4 != 0)
return nullptr;
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 == nullptr)
return nullptr;
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;
};
答案 12 :(得分：2)
EVP_EncodeBlock and EVP_DecodeBlock functions非常简单：
#include <stdio.h>
#include <stdlib.h>
#include <openssl/evp.h>
char *base64(const unsigned char *input, int length) {
const int pl = 4*((length+2)/3);
char *output = calloc(pl+1, 1); //+1 for the terminating null that EVP_EncodeBlock adds on
const int ol = EVP_EncodeBlock(output, input, length);
if (ol != pl) { fprintf(stderr, "Whoops, encode predicted %d but we got %d\n", pl, ol); }
return output;
}
unsigned char *decode64(const char *input, int length) {
const int pl = 3*length/4;
unsigned char *output = calloc(pl+1, 1);
const int ol = EVP_DecodeBlock(output, input, length);
if (pl != ol) { fprintf(stderr, "Whoops, decode predicted %d but we got %d\n", pl, ol); }
return output;
}
答案 13 :(得分：0)
如果您想找到可行的C解决方案，
我相信您需要this。
https://github.com/littlstar/b64.c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "b64.h"
int
main (void) {
unsigned char *str = "brian the monkey and bradley the kinkajou are friends";
char *enc = b64_encode(str, strlen(str));
printf("%s\n", enc); // YnJpYW4gdGhlIG1vbmtleSBhbmQgYnJhZGxleSB0aGUga2lua2Fqb3UgYXJlIGZyaWVuZHM=
char *dec = b64_decode(enc, strlen(enc));
printf("%s\n", dec); // brian the monkey and bradley the kinkajou are friends
free(enc);
free(dec);
return 0;
}
答案 14 :(得分：0)
我修复了@ryyst答案的错误，这是一个网址安全的版本：
'items' => [
[
'options' => ['title' => 'HELLO WORLD'],
'label' => Yii::t('lang', 'Browse'),
'url' => ['directory/index'],
'icon' => 'home',
'title' => 'HELLO WORLD'
],
答案 15 :(得分：0)
这是一种专门编写的解码器，通过直接写入putchar函数来避免需要缓冲区。这基于Wikibook的实现https://en.wikibooks.org/wiki/Algorithm_Implementation/Miscellaneous/Base64#C
这不像上面的其他选项那样容易使用。但是，它可以在嵌入式系统中使用，在这些系统中，您要转储一个大文件而不分配另一个大缓冲区来存储生成的base64 datauri字符串。 （很遗憾，datauri不允许您指定文件名）。
void datauriBase64EncodeBufferless(int (*putchar_fcptr)(int), const char* type_strptr, const void* data_buf, const size_t dataLength)
{
const char base64chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const uint8_t *data = (const uint8_t *)data_buf;
size_t x = 0;
uint32_t n = 0;
int padCount = dataLength % 3;
uint8_t n0, n1, n2, n3;
size_t outcount = 0;
size_t line = 0;
putchar_fcptr((int)'d');
putchar_fcptr((int)'a');
putchar_fcptr((int)'t');
putchar_fcptr((int)'a');
putchar_fcptr((int)':');
outcount += 5;
while (*type_strptr != '\0')
{
putchar_fcptr((int)*type_strptr);
type_strptr++;
outcount++;
}
putchar_fcptr((int)';');
putchar_fcptr((int)'b');
putchar_fcptr((int)'a');
putchar_fcptr((int)'s');
putchar_fcptr((int)'e');
putchar_fcptr((int)'6');
putchar_fcptr((int)'4');
putchar_fcptr((int)',');
outcount += 8;
/* increment over the length of the string, three characters at a time */
for (x = 0; x < dataLength; x += 3)
{
/* these three 8-bit (ASCII) characters become one 24-bit number */
n = ((uint32_t)data[x]) << 16; //parenthesis needed, compiler depending on flags can do the shifting before conversion to uint32_t, resulting to 0
if((x+1) < dataLength)
n += ((uint32_t)data[x+1]) << 8;//parenthesis needed, compiler depending on flags can do the shifting before conversion to uint32_t, resulting to 0
if((x+2) < dataLength)
n += data[x+2];
/* this 24-bit number gets separated into four 6-bit numbers */
n0 = (uint8_t)(n >> 18) & 63;
n1 = (uint8_t)(n >> 12) & 63;
n2 = (uint8_t)(n >> 6) & 63;
n3 = (uint8_t)n & 63;
/*
* if we have one byte available, then its encoding is spread
* out over two characters
*/
putchar_fcptr((int)base64chars[n0]);
putchar_fcptr((int)base64chars[n1]);
outcount += 2;
/*
* if we have only two bytes available, then their encoding is
* spread out over three chars
*/
if((x+1) < dataLength)
{
putchar_fcptr((int)base64chars[n2]);
outcount += 1;
}
/*
* if we have all three bytes available, then their encoding is spread
* out over four characters
*/
if((x+2) < dataLength)
{
putchar_fcptr((int)base64chars[n3]);
outcount += 1;
}
/* Breaking up the line so it's easier to copy and paste */
int curr_line = (outcount/80);
if( curr_line != line )
{
line = curr_line;
putchar_fcptr((int)'\r');
putchar_fcptr((int)'\n');
}
}
/*
* create and add padding that is required if we did not have a multiple of 3
* number of characters available
*/
if (padCount > 0)
{
for (; padCount < 3; padCount++)
{
putchar_fcptr((int)'=');
}
}
putchar_fcptr((int)'\r');
putchar_fcptr((int)'\n');
}
这是测试
#include <stdio.h>
#include <stdint.h>
#include <string.h>
int main(void)
{
char str[] = "test";
datauriBase64EncodeBufferless(putchar, "text/plain;charset=utf-8", str, strlen(str));
return 0;
}
预期输出：data:text/plain;charset=utf-8;base64,dGVzdA==
答案 16 :(得分：0)
此解决方案基于schulwitz答案（使用OpenSSL编码/解码），但它适用于C ++（嗯，原始问题是关于C，但这里已经有另外的C ++答案）并且它使用错误检查（所以它＆＃ 39;更安全使用）：
#include <openssl/bio.h>
std::string base64_encode(const std::string &input)
{
BIO *p_bio_b64 = nullptr;
BIO *p_bio_mem = nullptr;
try
{
// make chain: p_bio_b64 <--> p_bio_mem
p_bio_b64 = BIO_new(BIO_f_base64());
if (!p_bio_b64) { throw std::runtime_error("BIO_new failed"); }
BIO_set_flags(p_bio_b64, BIO_FLAGS_BASE64_NO_NL); //No newlines every 64 characters or less
p_bio_mem = BIO_new(BIO_s_mem());
if (!p_bio_mem) { throw std::runtime_error("BIO_new failed"); }
BIO_push(p_bio_b64, p_bio_mem);
// write input to chain
// write sequence: input -->> p_bio_b64 -->> p_bio_mem
if (BIO_write(p_bio_b64, input.c_str(), input.size()) <= 0)
{ throw std::runtime_error("BIO_write failed"); }
if (BIO_flush(p_bio_b64) <= 0)
{ throw std::runtime_error("BIO_flush failed"); }
// get result
char *p_encoded_data = nullptr;
auto encoded_len = BIO_get_mem_data(p_bio_mem, &p_encoded_data);
if (!p_encoded_data) { throw std::runtime_error("BIO_get_mem_data failed"); }
std::string result(p_encoded_data, encoded_len);
// clean
BIO_free_all(p_bio_b64);
return result;
}
catch (...)
{
if (p_bio_b64) { BIO_free_all(p_bio_b64); }
throw;
}
}
std::string base64_decode(const std::string &input)
{
BIO *p_bio_mem = nullptr;
BIO *p_bio_b64 = nullptr;
try
{
// make chain: p_bio_b64 <--> p_bio_mem
p_bio_b64 = BIO_new(BIO_f_base64());
if (!p_bio_b64) { throw std::runtime_error("BIO_new failed"); }
BIO_set_flags(p_bio_b64, BIO_FLAGS_BASE64_NO_NL); //Don't require trailing newlines
p_bio_mem = BIO_new_mem_buf((void*)input.c_str(), input.length());
if (!p_bio_mem) { throw std::runtime_error("BIO_new failed"); }
BIO_push(p_bio_b64, p_bio_mem);
// read result from chain
// read sequence (reverse to write): buf <<-- p_bio_b64 <<-- p_bio_mem
std::vector<char> buf((input.size()*3/4)+1);
std::string result;
for (;;)
{
auto nread = BIO_read(p_bio_b64, buf.data(), buf.size());
if (nread < 0) { throw std::runtime_error("BIO_read failed"); }
if (nread == 0) { break; } // eof
result.append(buf.data(), nread);
}
// clean
BIO_free_all(p_bio_b64);
return result;
}
catch (...)
{
if (p_bio_b64) { BIO_free_all(p_bio_b64); }
throw;
}
}
请注意，如果输入的base64序列不正确，base64_decode将返回空字符串（openssl以这种方式工作）。
答案 17 :(得分：-2)
这是针对接受的答案的编码器的优化版本，它还支持MIME和其他协议的换行符（可以将解析器优化应用于解码器）：
char *base64_encode(const unsigned char *data,
size_t input_length,
size_t *output_length,
bool addLineBreaks)
*output_length = 4 * ((input_length + 2) / 3);
if (addLineBreaks) *output_length += *output_length / 38; // CRLF after each 76 chars
char *encoded_data = malloc(*output_length);
if (encoded_data == NULL) return NULL;
UInt32 octet_a;
UInt32 octet_b;
UInt32 octet_c;
UInt32 triple;
int lineCount = 0;
int sizeMod = size - (size % 3); // check if there is a partial triplet
// adding all octet triplets, before partial last triplet
for (; offset < sizeMod; )
{
octet_a = data[offset++];
octet_b = data[offset++];
octet_c = data[offset++];
triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;
encoded_data[mBufferPos++] = encoding_table[(triple >> 3 * 6) & 0x3F];
encoded_data[mBufferPos++] = encoding_table[(triple >> 2 * 6) & 0x3F];
encoded_data[mBufferPos++] = encoding_table[(triple >> 1 * 6) & 0x3F];
encoded_data[mBufferPos++] = encoding_table[(triple >> 0 * 6) & 0x3F];
if (addLineBreaks)
{
if (++lineCount == 19)
{
encoded_data[mBufferPos++] = 13;
encoded_data[mBufferPos++] = 10;
lineCount = 0;
}
}
}
// last bytes
if (sizeMod < size)
{
octet_a = data[offset++]; // first octect always added
octet_b = offset < size ? data[offset++] : (UInt32)0; // conditional 2nd octet
octet_c = (UInt32)0; // last character is definitely padded
triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;
encoded_data[mBufferPos++] = encoding_table[(triple >> 3 * 6) & 0x3F];
encoded_data[mBufferPos++] = encoding_table[(triple >> 2 * 6) & 0x3F];
encoded_data[mBufferPos++] = encoding_table[(triple >> 1 * 6) & 0x3F];
encoded_data[mBufferPos++] = encoding_table[(triple >> 0 * 6) & 0x3F];
// add padding '='
sizeMod = size % 3;
// last character is definitely padded
encoded_data[mBufferPos - 1] = (byte)'=';
if (sizeMod == 1) encoded_data[mBufferPos - 2] = (byte)'=';
}
}