getopt.c

des算法实现源码

/*
 * Do not use this code unless you are compiling for MS-DOS.  It doesn't work
 * on unix.  I just found it somewhere on the net.  (D.A.B.  01-Apr-94)
 */
#include <stdio.h>
#include <string.h>

#ifdef __cpluscplus
extern "C" {
#endif

/*
 * get option letter from argument vector
 */
int     opterr = 1,             /* useless, never set or used */
        optind = 1,             /* index into parent argv vector */
        optopt;                 /* character checked for validity */
char    *optarg;                /* argument associated with option */

#define BADCH   (int)'?'
#define EMSG    ""
#define tell(s) fputs(*nargv,stderr);fputs(s,stderr); \
                fputc(optopt,stderr);fputc('\n',stderr);return(BADCH);

getopt(nargc,nargv,ostr)
int     nargc;
char    **nargv,
        *ostr;
{
        static char     *place = EMSG;  /* option letter processing */
        register char   *oli;           /* option letter list index */

        if(!*place) {                   /* update scanning pointer */
                if(optind >= nargc || *(place = nargv[optind]) != '-' 
	|| !*++place) return(EOF);
                if (*place == '-') {    /* found "--" */
                        ++optind;
                        return(EOF);
                }
        }                               /* option letter okay? */
        if ((optopt = (int)*place++) == (int)':' || !(oli =
strchr(ostr,optopt))
) {
                if(!*place) ++optind;
                tell(": illegal option -- ");
        }
        if (*++oli != ':') {            /* don't need argument */
                optarg = NULL;
                if (!*place) ++optind;
        }
        else {                          /* need an argument */
                if (*place) optarg = place;     /* no white space */

                else if (nargc <= ++optind) {   /* no arg */
                        place = EMSG;
                        tell(": option requires an argument -- ");
                }
                else optarg = nargv[optind];    /* white space */
                place = EMSG;
                ++optind;
        }
        return(optopt);                 /* dump back option letter */
}

#ifdef __cpluscplus
}
#endif