getopt.c

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#include "libc.h"
#include <lely/libc/unistd.h>
 
#if !LELY_HAVE_UNISTD_H
 
#include <assert.h>
#include <stddef.h>
#include <stdio.h>
 
char *optarg;
int optind = 1;
int opterr = 1;
int optopt;
 
static int optoff;
 
int
getopt(int argc, char *const argv[], const char *optstring)
{
        assert(argv);
        assert(optstring);
 
        optarg = NULL;
 
        // Check whether any arguments remain.
        if (optind >= argc || !argv[optind])
                return -1;
        // Continue with the next option in the current argument.
        char *cp = argv[optind] + optoff;
        // If this is a new argument, check if it is an option argument.
        if (!optoff) {
                // An option argument begins with '-'.
                if (*cp++ != '-' || !*cp)
                        return -1;
                // A double dash ("--") denotes the end of option arguments.
                if (*cp == '-' && !cp[1]) {
                        optind++;
                        return -1;
                }
                optoff = 1;
        }
        int c = *cp++;
        // Update the index and offset of the next option.
        if (*cp) {
                optoff++;
        } else {
                optind++;
                optoff = 0;
        }
 
        // Check if the option character occurs in `optstring`.
        const char *op = optstring;
        while (*op && (*op == ':' || *op == '?' || *op != c))
                op++;
        if (!*op) {
                optopt = c;
                if (opterr && *optstring != ':')
                        fprintf(stderr, "%s: illegal option -- %c\n", argv[0],
                                        optopt);
                return '?';
        }
 
        // If the option does not take an argument, we are done.
        if (*++op != ':')
                return c;
 
        optind++;
        optoff = 0;
        if (*cp) {
                // If any characters remain in the current argument, they form
                // the argument for the option...
                optarg = cp;
        } else {
                // ... otherwise, the next argument is used, if it exists.
                if (optind > argc) {
                        optopt = c;
                        if (opterr && *optstring != ':')
                                fprintf(stderr,
                                                "%s: option requires an "
                                                "argument -- %c\n",
                                                argv[0], optopt);
                        return *optstring == ':' ? ':' : '?';
                }
                optarg = argv[optind - 1];
        }
        return c;
}
 
#endif // !LELY_HAVE_UNISTD_H