base64编码解码的实现(C语言)

王朝vc·作者佚名  2006-01-08
窄屏简体版  字體: |||超大  

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

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);

}

 
 
 
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