/* base64.c: MIME BASE64编码与解码器,读标准输入. 赵建军, 2000.1.12.a */
/* 2000.2.19.A: 增文件处理. */
#include "stdio.h"
#include "string.h"
#include "stdlib.h"
#include "ctype.h"
char *base="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
union
{
struct
{
unsigned long d:6;
unsigned long c:6;
unsigned long b:6;
unsigned long a:6;
}s;
unsigned char c[3];
}u;
int decode=0;
main(int argc,char **argv)
{
extern char *optarg;
extern int optind;
int c;
FILE *fp;
while ((c=getopt(argc,argv,"u"))!=EOF)
{
switch(c)
{
case 'u': decode=1; break;
default: usage(); break;
}
}
if (argc==optind)
{
if (isatty(0)) usage();
if (decode) base64decode(stdin,stdout); else base64encode(stdin,stdout);
}
else
for (;optind<argc;optind++)
{
fp=fopen(argv[optind],"r");
if (fp==0) { fprintf(stderr,"%s: fopen %s error.\n",argv[0],argv[optind]); continue; }
if (decode) base64decode(fp,stdout); else base64encode(fp,stdout);
fclose(fp);
}
exit(0);
}
usage()
{
fprintf(stderr,"base64: MIME BASE64 encoder and decoder, by zzz ( ) at 2000.1.11.m\n");
fprintf(stderr,"Usage: base64 [-u] [file1] [file2] ...\n");
exit(1);
}
base64encode(FILE *fp,FILE *fq)
{
int ch,n,h=0,flag=0;
while (1)
{
u.c[0]=u.c[1]=u.c[2]=0;
for (n=0;n<3;n++)
{
ch=fgetc(fp);
if (ch==EOF) break;
u.c[2-n]=ch;
}
if (n==0) break;
flag=1;
switch(n)
{
case 1: fprintf(fq,"%c%c==",base[u.s.a],base[u.s.b]);break;
case 2: fprintf(fq,"%c%c%c=",base[u.s.a],base[u.s.b],base[u.s.c]);break;
case 3: fprintf(fq,"%c%c%c%c",base[u.s.a],base[u.s.b],base[u.s.c],base[u.s.d]);break;
}
if (h==15) { h=0; fprintf(fq,"\n"); } else h++;
}
if (flag&&h) fprintf(fq,"\n");
}
base64decode(FILE *fp,FILE *fq)
{
int c1,c2,c3,c4;
while (1)
{
/* c1 */
c1=fgetc(fp);
while (c1!=EOF&&isspace(c1)) c1=fgetc(fp);
if (c1==EOF) break;
if (strchr(base,c1)==NULL&&c1!='=')
{
fprintf(fq,"Error: %c : not BASE64 code!\n",c1);
return 1;
}
/* c2 */
c2=fgetc(fp);
if (c2==EOF)
{
fprintf(fq,"Error: unexpected EOF in BASE64 code!\n");
return 1;
}
if (strchr(base,c2)==NULL&&c2!='=')
{
fprintf(fq,"Error: %c : not BASE64 code!\n",c2);
return 1;
}
/* c3 */
c3=fgetc(fp);
if (c3==EOF)
{
fprintf(fq,"Error: unexpected EOF in BASE64 code!\n");
return 1;
}
if (strchr(base,c3)==NULL&&c3!='=')
{
fprintf(fq,"Error: %c : not BASE64 code!\n",c3);
return 1;
}
/* c4 */
c4=fgetc(fp);
if (c4==EOF)
{
fprintf(fq,"Error: unexpected EOF in BASE64 code!\n");
return 1;
}
if (strchr(base,c4)==NULL&&c4!='=')
{
fprintf(fq,"Error: %c : not BASE64 code!\n",c4);
return 1;
}
/* check format:[A-Za-z0-9+/][A-Za-z0-9+/][A-Za-z0-9+/=][A-Za-z0-9+/=] */
if (strchr(base,c1)&&strchr(base,c2)&&(strchr(base,c3)||c3=='=')&&
((c3=='='&&c4=='=')||(c3!='='&&(c4=='='||strchr(base,c4)))))
{
u.s.a=strchr(base,c1)-base;
u.s.b=strchr(base,c2)-base;
if (c3=='=')
{
/* one byte output */
fprintf(fq,"%c",u.c[2]);
}
else
if (c4=='=')
{
/* two byte output */
u.s.c=strchr(base,c3)-base;
fprintf(fq,"%c%c",u.c[2],u.c[1]);
}
else
{
/* three byte output */
u.s.c=strchr(base,c3)-base;
u.s.d=strchr(base,c4)-base;
fprintf(fq,"%c%c%c",u.c[2],u.c[1],u.c[0]);
}
}
else
{
fprintf(fq,"Error: %c%c%c%c : not BASE64 code!\n",c1,c2,c3,c4);
return 1;
}
}
return 0;
}