Base64编码解码的实现(C语言)

base64编码解码的实现(C语言)

　/****************************************************************

This is a sample routine of base64 algorithm.The goal is to

illustrate principles,so some details may be ignored.

Author email:zhangwu2003@163.com

*****************************************************************/

#include <stdio.h>

#include <string.h>

#include <malloc.h>

char*

ch64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

unsigned char *encode(unsigned char *src,int srclen)

{

int n,buflen,i,j;

int pading=0;

unsigned char *buf;

static unsigned char *dst;

buf=src;

buflen=n=srclen;

if(n%3!=0)   /* pad with ´=´ by using a temp buffer */

{

   pading=1;

   buflen=n+3-n%3;

   buf=malloc(buflen+1);

   memset(buf,0,buflen+1);

   memcpy(buf,src,n);

   for(i=0;i<3-n%3;i++)

    buf[n+i]=´=´;

}

dst=malloc(buflen*4/3+1);

memset(dst,0,buflen*4/3+1);

for(i=0,j=0;i<buflen;i+=3,j+=4)

{

   dst[j]=(buf[i]&0xFC)>>2;

   dst[j+1]=((buf[i]&0x03)<<4) + ((buf[i+1]&0xF0)>>4);

   dst[j+2]=((buf[i+1]&0x0F)<<2) + ((buf[i+2]&0xC0)>>6);

   dst[j+3]=buf[i+2]&0x3F;

}

for(i=0;i<buflen*4/3;i++) /* map 6 bit value to base64 ASCII character */

   dst[i]=ch64[dst[i]];

if(pading)

   free(buf);

return dst;

}

unsigned char *decode(unsigned char *src)

{

int n,i,j;

unsigned char *p;

static unsigned char *dst;

n=strlen(src);

for(i=0;i<n;i++) /* map base64 ASCII character to 6 bit value */

{

   p=strchr(ch64,src[i]);

   if(!p)

    break;

   src[i]=p-ch64;

}

dst=malloc(n*3/4+1);

memset(dst,0,n*3/4+1);

for(i=0,j=0;i<n;i+=4,j+=3)

{

   dst[j]=(src[i]<<2) + ((src[i+1]&0x30)>>4);

   dst[j+1]=((src[i+1]&0x0F)<<4) + ((src[i+2]&0x3C)>>2);

   dst[j+2]=((src[i+2]&0x03)<<6) + src[i+3];

}

return dst;

}

void main()

{

// char *src="zhangwu张武";

char src[]={´1´,´2´,´3´,0,´a´,´b´,´*´,0,´A´,´B´,´$´};

unsigned char *dst1;

unsigned char *dst2;

unsigned int i;

dst1=encode(src,11); /* the second parameter must accord with the first one */

printf("%s/n",dst1);

dst2=decode(dst1);

for(i=0;i<_msize(dst2);i++)

   printf("%c",dst2[i]);

free(dst1);

free(dst2);

}

 

=================

 

base64编码的实现

int Base64Enc(char *buf, char*text,int size)
{
static char *base64_encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
int buflen = 0;

while(size>0)
{
*buf++ = base64_encoding[ (text[0] >> 2 ) & 0x3f];
if(size>2)
{
*buf++ = base64_encoding[((text[0] & 3) << 4) | (text[1] >> 4)];
*buf++ = base64_encoding[((text[1] & 0xF) << 2) | (text[2] >> 6)];
*buf++ = base64_encoding[text[2] & 0x3F];
}
else
{
switch(size)
{
case 1:
*buf++ = base64_encoding[(text[0] & 3) << 4 ];
*buf++ = '=';
*buf++ = '=';
break;
case 2:
*buf++ = base64_encoding[((text[0] & 3) << 4) | (text[1] >> 4)];
*buf++ = base64_encoding[((text[1] & 0x0F) << 2) | (text[2] >> 6)];
*buf++ = '=';
break;
}
}

text +=3;
size -=3;
buflen +=4;
}

*buf = 0;
return buflen;
}

base64解码的实现

char GetBase64Value(char ch)
{
if ((ch >= 'A') && (ch <= 'Z'))
return ch - 'A';
if ((ch >= 'a') && (ch <= 'z'))
return ch - 'a' + 26;
if ((ch >= '0') && (ch <= '9'))
return ch - '0' + 52;
switch (ch)
{
case '+':
return 62;
case '/':
return 63;
case '=': /* base64 padding */
return 0;
default:
return 0;
}
}

//进行base64解码输入应该是4的倍数(根据mime标准)
//如果不是4倍数返回错误
//注意 如果是最后一个字符 那么长度不准备 可能会多1
//返回buf长度
int Base64Dec(char *buf,char*text,int size)
{
if(size%4)
return -1;
unsigned char chunk[4];
int parsenum=0;

while(size>0)
{
chunk[0] = GetBase64Value(text[0]);
chunk[1] = GetBase64Value(text[1]);
chunk[2] = GetBase64Value(text[2]);
chunk[3] = GetBase64Value(text[3]);

*buf++ = (chunk[0] << 2) | (chunk[1] >> 4);
*buf++ = (chunk[1] << 4) | (chunk[2] >> 2);
*buf++ = (chunk[2] << 6) | (chunk[3]);

text+=4;
size-=4;
parsenum+=3;
}

return parsenum;
}