base64_de.txt

编码方式的解码示范uuencode and uudecode are in the public domain. dos2unix and unix2dos are hereby placed in

#include <stdio.h>

unsigned char rev(char t)
{    if(t>='A' && t<='Z')
		return t-'A';
	 if(t>='a' && t<='z')
		return t-'a'+26;
	 if(t>='0' && t<='9')
		return t-'0'+52;
	 if(t=='+') return 62;
	 if(t=='/') return 63;
	 printf("\nRead %c, error\n",t);
}

void Usage(void)
{
   printf("\nUsage: debase64 inputfilename outputfilename\n");
   printf("Note:  to use debase64, you need first edit your file,\n"
	    "       leave only the code part.\n");
   printf("For Example, if you have a file with contents:\n"
   "Content-Type: APPLICATION/octet-stream; name=\"ping.exe\"\n"
   "Content-Transfer-Encoding: BASE64\n"
   "Content-Description:\n"
   "\n"
   "TVrnAS4AAAAJAAMH//+/BQAEAAAAAfD/UAAAAAUhUEtMSVRFIENvcHIuIDE5\n"
   "/Ou8HfwA/F/HFfzfsSr8dmyk/B17ufzOx9H843F2/PjcHfwN/E/HIvzb8Tf8\n"
   "dfxM/B1/Yfz/x9/8//F3/P/8Hfz//H/H//zf8f/8d/z//B1///z/x9/8//F3\n"
   "/P/8Hfz//H/H//zf8f/8d/z/XB0A//8BAAABAACxC4AAAAAAAA==\n"
   "--944387211-851401618-859988490=:5693--\n");
   printf("\nYou need to edit it, just leave the following:\n"
   "TVrnAS4AAAAJAAMH//+/BQAEAAAAAfD/UAAAAAUhUEtMSVRFIENvcHIuIDE5\n"
   "/Ou8HfwA/F/HFfzfsSr8dmyk/B17ufzOx9H843F2/PjcHfwN/E/HIvzb8Tf8\n"
   "dfxM/B1/Yfz/x9/8//F3/P/8Hfz//H/H//zf8f/8d/z//B1///z/x9/8//F3\n"
   "/P/8Hfz//H/H//zf8f/8d/z/XB0A//8BAAABAACxC4AAAAAAAA==\n");
   exit(0);
}

main(int argc, char *argv[])
{   FILE * fpin,*fpout;
	unsigned char buff[500];
	int len,i;
	unsigned long tmp;
	if(argc!=3)
	   Usage();
	fpin=fopen(argv[1],"r");
	if(fpin==NULL)
	{ printf("\nOpen input file %s error\n",argv[1]);
	  exit(2);
	}
	fpout=fopen(argv[2],"wb");
	if(fpout==NULL)
	{ printf("\nOpen output file %s error\n",argv[2]);
	  exit(2);
	}
	while(fgets(buff,400,fpin)!=NULL)
	{   len=strlen(buff);
		if(len<4) break;
		if(buff[len-1]=='\n') len--;
		tmp=0;
		for(i=0;i+4<=len;i+=4)
		{   tmp=rev(*(buff+i));
			tmp=(tmp<<6)+rev(*(buff+i+1));
			tmp=(tmp<<6)+rev(*(buff+i+2));
			tmp=(tmp<<6)+rev(*(buff+i+3));
			*(buff)=(tmp>>16)&0xff;
			*(buff+1)=(tmp>>8)&0xff;
			*(buff+2)=tmp &0xff;
			fwrite(buff,1,3,fpout);
		}
	}
	fclose(fpin);
	fclose(fpout);
}