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      1 /*
      2  * getopt.c
      3  *
      4  * Simple POSIX getopt(), no GNU extensions...
      5  */
      6 
      7 #include <stdint.h>
      8 #include <unistd.h>
      9 #include <string.h>
     10 
     11 char *optarg;
     12 int optind, opterr, optopt;
     13 static struct getopt_private_state {
     14 	const char *optptr;
     15 	const char *last_optstring;
     16 	char *const *last_argv;
     17 } pvt;
     18 
     19 int getopt(int argc, char *const *argv, const char *optstring)
     20 {
     21 	const char *carg;
     22 	const char *osptr;
     23 	int opt;
     24 
     25 	/* getopt() relies on a number of different global state
     26 	   variables, which can make this really confusing if there is
     27 	   more than one use of getopt() in the same program.  This
     28 	   attempts to detect that situation by detecting if the
     29 	   "optstring" or "argv" argument have changed since last time
     30 	   we were called; if so, reinitialize the query state. */
     31 
     32 	if (optstring != pvt.last_optstring || argv != pvt.last_argv ||
     33 	    optind < 1 || optind > argc) {
     34 		/* optind doesn't match the current query */
     35 		pvt.last_optstring = optstring;
     36 		pvt.last_argv = argv;
     37 		optind = 1;
     38 		pvt.optptr = NULL;
     39 	}
     40 
     41 	carg = argv[optind];
     42 
     43 	/* First, eliminate all non-option cases */
     44 
     45 	if (!carg || carg[0] != '-' || !carg[1]) {
     46 		return -1;
     47 	}
     48 
     49 	if (carg[1] == '-' && !carg[2]) {
     50 		optind++;
     51 		return -1;
     52 	}
     53 
     54 	if ((uintptr_t) (pvt.optptr - carg) > (uintptr_t) strlen(carg)) {
     55 		/* Someone frobbed optind, change to new opt. */
     56 		pvt.optptr = carg + 1;
     57 	}
     58 
     59 	opt = *pvt.optptr++;
     60 
     61 	if (opt != ':' && (osptr = strchr(optstring, opt))) {
     62 		if (osptr[1] == ':') {
     63 			if (*pvt.optptr) {
     64 				/* Argument-taking option with attached
     65 				   argument */
     66 				optarg = (char *)pvt.optptr;
     67 				optind++;
     68 			} else {
     69 				/* Argument-taking option with non-attached
     70 				   argument */
     71 				if (argv[optind + 1]) {
     72 					optarg = (char *)argv[optind+1];
     73 					optind += 2;
     74 				} else {
     75 					/* Missing argument */
     76 					optind++;
     77 					return (optstring[0] == ':')
     78 						? ':' : '?';
     79 				}
     80 			}
     81 			return opt;
     82 		} else {
     83 			/* Non-argument-taking option */
     84 			/* pvt.optptr will remember the exact position to
     85 			   resume at */
     86 			if (!*pvt.optptr)
     87 				optind++;
     88 			return opt;
     89 		}
     90 	} else {
     91 		/* Unknown option */
     92 		optopt = opt;
     93 		if (!*pvt.optptr)
     94 			optind++;
     95 		return '?';
     96 	}
     97 }
     98