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
11char *optarg;
12int optind, opterr, optopt;
13static struct getopt_private_state {
14	const char *optptr;
15	const char *last_optstring;
16	char *const *last_argv;
17} pvt;
18
19int 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