c++如何实现Base64算法
- 作者: 优衣库库长丶
- 来源: 51数据库
- 2021-08-13
base64用途
1.用于对soho级路由器（网关设备）管理员帐户密码的加密
2.流媒体网站对于播放的流媒体文件的路径的加密
3.迅雷等下载软件对下载链接地址的加密
base64算法
base64编码要求把3个8位字节（3*8=24）转化为4个6位的字节（4*6=24），之后在6位的前面补两个0，形成8位一个字节的形式。
base64类
函数：
unsigned int creatematchingencodingbuffer (unsigned int p_inputbytecount, char** p_ppencodingbuffer);
创建匹配于编码的缓存空间。参数：1输入字节数，2进行编码需要的缓存空间；返回值：缓存空间大小。
unsigned int creatematchingdecodingbuffer (char* p_pinputbufferstring, char** p_ppdecodingbuffer);
创建匹配于解码的缓存空间。参数：1解码对象缓存，2进行解码需要的缓存空间；返回值：缓存空间大小。
void encodebuffer (char* p_pinputbuffer, unsigned int p_inputbufferlength, char* p_poutputbufferstring);
进行编码。参数：1明文，2明文长度，3密文输出。
unsigned int decodebuffer (char* p_pinputbufferstring, char* p_poutputbuffer);
进行解码。参数：1密文，2明文；返回值：明文长度
c++实现：
头文件：
view code
/************************************************
* *
* cbase64.h *
* base 64 de- and encoding class *
* *
* ============================================ *
* *
* this class was written on 28.05.2003 *
* by jan raddatz [jan-raddatz@web.de] *
* *
* ============================================ *
* *
* copyright (c) by jan raddatz *
* this class was published @ codeguru.com *
* 28.05.2003 *
* *
************************************************/
#pragma once
#include <afx.h>
#include <stdlib.h>
#include <math.h>
#include <memory.h>
const static unsigned int max_line_length = 76;
const static char base64_alphabet [64] =
{
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', // 0 - 9
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', // 10 - 19
'u', 'v', 'w', 'x', 'y', 'z', 'a', 'b', 'c', 'd', // 20 - 29
'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 30 - 39
'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', // 40 - 49
'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', // 50 - 59
'8', '9', '+', '/' // 60 - 63
};
const static char base64_dealphabet [128] =
{
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0 - 9
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 10 - 19
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20 - 29
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 30 - 39
0, 0, 0, 62, 0, 0, 0, 63, 52, 53, // 40 - 49
54, 55, 56, 57, 58, 59, 60, 61, 0, 0, // 50 - 59
0, 61, 0, 0, 0, 0, 1, 2, 3, 4, // 60 - 69
5, 6, 7, 8, 9, 10, 11, 12, 13, 14, // 70 - 79
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 80 - 89
25, 0, 0, 0, 0, 0, 0, 26, 27, 28, // 90 - 99
29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // 100 - 109
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, // 110 - 119
49, 50, 51, 0, 0, 0, 0, 0 // 120 - 127
};
enum
{
unable_to_open_input_file,
unable_to_open_output_file,
unable_to_create_outputbuffer
};
class cbase64
{
public:
cbase64 ();
unsigned int calculaterecquiredencodeoutputbuffersize (unsigned int p_inputbytecount);
unsigned int calculaterecquireddecodeoutputbuffersize (char* p_pinputbufferstring);
void encodebytetriple (char* p_pinputbuffer, unsigned int inputcharacters, char* p_poutputbuffer);
unsigned int decodebytequartet (char* p_pinputbuffer, char* p_poutputbuffer);
void encodebuffer (char* p_pinputbuffer, unsigned int p_inputbufferlength, char*p_poutputbufferstring);
unsigned int decodebuffer (char* p_pinputbufferstring, char* p_poutputbuffer);
unsigned int creatematchingencodingbuffer (unsigned int p_inputbytecount, char** p_ppencodingbuffer);
unsigned int creatematchingdecodingbuffer (char* p_pinputbufferstring, char** p_ppdecodingbuffer);
unsigned int encodefile (char* p_psourcefilename, char* p_pencodedfilename);
unsigned int decodefile (char* p_psourcefilename, char* p_pdecodedfilename);
};
cpp文件：
view code
/************************************************
* *
* cbase64.cpp *
* base 64 de- and encoding class *
* *
* ============================================ *
* *
* this class was written on 28.05.2003 *
* by jan raddatz [jan-raddatz@web.de] *
* *
* ============================================ *
* *
* copyright (c) by jan raddatz *
* this class was published @ codeguru.com *
* 28.05.2003 *
* *
************************************************/
#include "stdafx.h"
#include "cbase64.h"
cbase64::cbase64 ()
{
}
unsigned int cbase64::calculaterecquiredencodeoutputbuffersize (unsigned int p_inputbytecount)
{
div_t result = div (p_inputbytecount, 3);
unsigned int recquiredbytes = 0;
if (result.rem == 0)
{
// number of encoded characters
recquiredbytes = result.quot * 4;
// crlf -> "\r\n" each 76 characters
result = div (recquiredbytes, 76);
recquiredbytes += result.quot * 2;
// terminating null for the encoded string
recquiredbytes += 1;
return recquiredbytes;
}
else
{
// number of encoded characters
recquiredbytes = result.quot * 4 + 4;
// crlf -> "\r\n" each 76 characters
result = div (recquiredbytes, 76);
recquiredbytes += result.quot * 2;
// terminating null for the encoded string
recquiredbytes += 1;
return recquiredbytes;
}
}
unsigned int cbase64::calculaterecquireddecodeoutputbuffersize (char* p_pinputbufferstring)
{
unsigned int bufferlength = strlen (p_pinputbufferstring);
div_t result = div (bufferlength, 4);
if (p_pinputbufferstring [bufferlength - 1] != '=')
{
return result.quot * 3;
}
else
{
if (p_pinputbufferstring [bufferlength - 2] == '=')
{
return result.quot * 3 - 2;
}
else
{
return result.quot * 3 - 1;
}
}
}
void cbase64::encodebytetriple (char* p_pinputbuffer, unsigned int inputcharacters, char* p_poutputbuffer)
{
unsigned int mask = 0xfc000000;
unsigned int buffer = 0;
char* temp = (char*) &buffer;
temp [3] = p_pinputbuffer [0];
if (inputcharacters > 1)
temp [2] = p_pinputbuffer [1];
if (inputcharacters > 2)
temp [1] = p_pinputbuffer [2];
switch (inputcharacters)
{
case 3:
{
p_poutputbuffer [0] = base64_alphabet [(buffer & mask) >> 26];
buffer = buffer << 6;
p_poutputbuffer [1] = base64_alphabet [(buffer & mask) >> 26];
buffer = buffer << 6;
p_poutputbuffer [2] = base64_alphabet [(buffer & mask) >> 26];
buffer = buffer << 6;
p_poutputbuffer [3] = base64_alphabet [(buffer & mask) >> 26];
break;
}
case 2:
{
p_poutputbuffer [0] = base64_alphabet [(buffer & mask) >> 26];
buffer = buffer << 6;
p_poutputbuffer [1] = base64_alphabet [(buffer & mask) >> 26];
buffer = buffer << 6;
p_poutputbuffer [2] = base64_alphabet [(buffer & mask) >> 26];
p_poutputbuffer [3] = '=';
break;
}
case 1:
{
p_poutputbuffer [0] = base64_alphabet [(buffer & mask) >> 26];
buffer = buffer << 6;
p_poutputbuffer [1] = base64_alphabet [(buffer & mask) >> 26];
p_poutputbuffer [2] = '=';
p_poutputbuffer [3] = '=';
break;
}
}
}
unsigned int cbase64::decodebytequartet (char* p_pinputbuffer, char* p_poutputbuffer)
{
unsigned int buffer = 0;
if (p_pinputbuffer[3] == '=')
{
if (p_pinputbuffer[2] == '=')
{
buffer = (buffer | base64_dealphabet [p_pinputbuffer[0]]) << 6;
buffer = (buffer | base64_dealphabet [p_pinputbuffer[1]]) << 6;
buffer = buffer << 14;
char* temp = (char*) &buffer;
p_poutputbuffer [0] = temp [3];
return 1;
}
else
{
buffer = (buffer | base64_dealphabet [p_pinputbuffer[0]]) << 6;
buffer = (buffer | base64_dealphabet [p_pinputbuffer[1]]) << 6;
buffer = (buffer | base64_dealphabet [p_pinputbuffer[2]]) << 6;
buffer = buffer << 8;
char* temp = (char*) &buffer;
p_poutputbuffer [0] = temp [3];
p_poutputbuffer [1] = temp [2];
return 2;
}
}
else
{
buffer = (buffer | base64_dealphabet [p_pinputbuffer[0]]) << 6;
buffer = (buffer | base64_dealphabet [p_pinputbuffer[1]]) << 6;
buffer = (buffer | base64_dealphabet [p_pinputbuffer[2]]) << 6;
buffer = (buffer | base64_dealphabet [p_pinputbuffer[3]]) << 6;
buffer = buffer << 2;
char* temp = (char*) &buffer;
p_poutputbuffer [0] = temp [3];
p_poutputbuffer [1] = temp [2];
p_poutputbuffer [2] = temp [1];
return 3;
}
return -1;
}
void cbase64::encodebuffer(char* p_pinputbuffer, unsigned int p_inputbufferlength, char* p_poutputbufferstring)
{
unsigned int finishedbytequartetsperline = 0;
unsigned int inputbufferindex = 0;
unsigned int outputbufferindex = 0;
memset (p_poutputbufferstring, 0, calculaterecquiredencodeoutputbuffersize (p_inputbufferlength));
while (inputbufferindex < p_inputbufferlength)
{
if (p_inputbufferlength - inputbufferindex <= 2)
{
finishedbytequartetsperline ++;
encodebytetriple (p_pinputbuffer + inputbufferindex, p_inputbufferlength - inputbufferindex, p_poutputbufferstring + outputbufferindex);
break;
}
else
{
finishedbytequartetsperline++;
encodebytetriple (p_pinputbuffer + inputbufferindex, 3, p_poutputbufferstring + outputbufferindex);
inputbufferindex += 3;
outputbufferindex += 4;
}
if (finishedbytequartetsperline == 19)
{
p_poutputbufferstring [outputbufferindex ] = '\r';
p_poutputbufferstring [outputbufferindex+1] = '\n';
p_poutputbufferstring += 2;
finishedbytequartetsperline = 0;
}
}
}
unsigned int cbase64::decodebuffer (char* p_pinputbufferstring, char* p_poutputbuffer)
{
unsigned int inputbufferindex = 0;
unsigned int outputbufferindex = 0;
unsigned int inputbufferlength = strlen (p_pinputbufferstring);
char bytequartet [4];
while (inputbufferindex < inputbufferlength)
{
for (int i = 0; i < 4; i++)
{
bytequartet [i] = p_pinputbufferstring [inputbufferindex];
// ignore all characters except the ones in base64_alphabet
if ((bytequartet [i] >= 48 && bytequartet [i] <= 57) ||
(bytequartet [i] >= 65 && bytequartet [i] <= 90) ||
(bytequartet [i] >= 97 && bytequartet [i] <= 122) ||
bytequartet [i] == '+' || bytequartet [i] == '/' || bytequartet [i] == '=')
{
}
else
{
// invalid character
i--;
}
inputbufferindex++;
}
outputbufferindex += decodebytequartet (bytequartet, p_poutputbuffer + outputbufferindex);
}
// outputbufferindex gives us the next position of the next decoded character
// inside our output buffer and thus represents the number of decoded characters
// in our buffer.
return outputbufferindex;
}
unsigned int cbase64::creatematchingencodingbuffer (unsigned int p_inputbytecount, char** p_ppencodingbuffer)
{
unsigned int size = calculaterecquiredencodeoutputbuffersize (p_inputbytecount);
(*p_ppencodingbuffer) = (char*) malloc (size);
memset (*p_ppencodingbuffer, 0, size);
return size;
}
unsigned int cbase64::creatematchingdecodingbuffer (char* p_pinputbufferstring, char** p_ppdecodingbuffer)
{
unsigned int size = calculaterecquireddecodeoutputbuffersize (p_pinputbufferstring);
(*p_ppdecodingbuffer) = (char*) malloc (size+1);
memset (*p_ppdecodingbuffer, 0, size+1);
return size+1;
}
unsigned int cbase64::encodefile (char* p_psourcefilename, char* p_pencodedfilename)
{
cfile inputfile;
cfile outputfile;
if (!inputfile.open (p_psourcefilename, cfile::moderead))
return unable_to_open_input_file;
if (!outputfile.open (p_pencodedfilename, cfile::modecreate|cfile::modewrite))
return unable_to_open_output_file;
char inputbuffer [19 * 3];
char* poutputbuffer;
creatematchingencodingbuffer (sizeof (inputbuffer), &poutputbuffer);
if (poutputbuffer == 0)
return unable_to_create_outputbuffer;
unsigned int readbytes = 0;
while ((readbytes = inputfile.read (inputbuffer, sizeof (inputbuffer))) != 0)
{
encodebuffer (inputbuffer, readbytes, poutputbuffer);
outputfile.write (poutputbuffer, strlen (poutputbuffer));
}
outputfile.flush ();
outputfile.close ();
inputfile.close ();
return 0;
}
unsigned int cbase64::decodefile (char* p_psourcefilename, char* p_pdecodedfilename)
{
cstdiofile inputfile;
cfile outputfile;
if (!inputfile.open (p_psourcefilename, cfile::moderead))
return unable_to_open_input_file;
if (!outputfile.open (p_pdecodedfilename, cfile::modecreate|cfile::modewrite))
return unable_to_open_output_file;
cstring inputbuffer;
char outputbuffer[64];
unsigned int readbytes = 0;
while ((readbytes = inputfile.readstring (inputbuffer)) != 0)
{
inputbuffer.remove ('\r');
inputbuffer.remove ('\n');
unsigned int decodedbytes = decodebuffer ((lptstr) (lpctstr) inputbuffer, outputbuffer);
outputfile.write (&outputbuffer [0], decodedbytes);
}
outputfile.flush ();
outputfile.close ();
inputfile.close ();
return 0;
}
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