source: azure_iot_hub/trunk/musl-1.1.18/src/misc/getopt_long.c@ 388

#define _GNU_SOURCE
#include <stddef.h>
#include <getopt.h>
#include <stdio.h>
#include <string.h>

extern int __optpos, __optreset;

static void permute(char *const *argv, int dest, int src)
{
        char **av = (char **)argv;
        char *tmp = av[src];
        int i;
        for (i=src; i>dest; i--)
                av[i] = av[i-1];
        av[dest] = tmp;
}

void __getopt_msg(const char *, const char *, const char *, size_t);

static int __getopt_long_core(int argc, char *const *argv, const char *optstring, const struct option *longopts, int *idx, int longonly);

static int __getopt_long(int argc, char *const *argv, const char *optstring, const struct option *longopts, int *idx, int longonly)
{
        int ret, skipped, resumed;
        if (!optind || __optreset) {
                __optreset = 0;
                __optpos = 0;
                optind = 1;
        }
        if (optind >= argc || !argv[optind]) return -1;
        skipped = optind;
        if (optstring[0] != '+' && optstring[0] != '-') {
                int i;
                for (i=optind; ; i++) {
                        if (i >= argc || !argv[i]) return -1;
                        if (argv[i][0] == '-' && argv[i][1]) break;
                }
                optind = i;
        }
        resumed = optind;
        ret = __getopt_long_core(argc, argv, optstring, longopts, idx, longonly);
        if (resumed > skipped) {
                int i, cnt = optind-resumed;
                for (i=0; i<cnt; i++)
                        permute(argv, skipped, optind-1);
                optind = skipped + cnt;
        }
        return ret;
}

static int __getopt_long_core(int argc, char *const *argv, const char *optstring, const struct option *longopts, int *idx, int longonly)
{
        optarg = 0;
        if (longopts && argv[optind][0] == '-' &&
                ((longonly && argv[optind][1] && argv[optind][1] != '-') ||
                 (argv[optind][1] == '-' && argv[optind][2])))
        {
                int colon = optstring[optstring[0]=='+'||optstring[0]=='-']==':';
                int i, cnt, match;
                char *opt;
                for (cnt=i=0; longopts[i].name; i++) {
                        const char *name = longopts[i].name;
                        opt = argv[optind]+1;
                        if (*opt == '-') opt++;
                        for (; *name && *name == *opt; name++, opt++);
                        if (*opt && *opt != '=') continue;
                        match = i;
                        if (!*name) {
                                cnt = 1;
                                break;
                        }
                        cnt++;
                }
                if (cnt==1) {
                        i = match;
                        optind++;
                        if (*opt == '=') {
                                if (!longopts[i].has_arg) {
                                        optopt = longopts[i].val;
                                        if (colon || !opterr)
                                                return '?';
                                        __getopt_msg(argv[0],
                                                ": option does not take an argument: ",
                                                longopts[i].name,
                                                strlen(longopts[i].name));
                                        return '?';
                                }
                                optarg = opt+1;
                        } else if (longopts[i].has_arg == required_argument) {
                                if (!(optarg = argv[optind])) {
                                        optopt = longopts[i].val;
                                        if (colon) return ':';
                                        if (!opterr) return '?';
                                        __getopt_msg(argv[0],
                                                ": option requires an argument: ",
                                                longopts[i].name,
                                                strlen(longopts[i].name));
                                        return '?';
                                }
                                optind++;
                        }
                        if (idx) *idx = i;
                        if (longopts[i].flag) {
                                *longopts[i].flag = longopts[i].val;
                                return 0;
                        }
                        return longopts[i].val;
                }
                if (argv[optind][1] == '-') {
                        optopt = 0;
                        if (!colon && opterr)
                                __getopt_msg(argv[0], cnt ?
                                        ": option is ambiguous: " :
                                        ": unrecognized option: ",
                                        argv[optind]+2,
                                        strlen(argv[optind]+2));
                        optind++;
                        return '?';
                }
        }
        return getopt(argc, argv, optstring);
}

int getopt_long(int argc, char *const *argv, const char *optstring, const struct option *longopts, int *idx)
{
        return __getopt_long(argc, argv, optstring, longopts, idx, 0);
}

int getopt_long_only(int argc, char *const *argv, const char *optstring, const struct option *longopts, int *idx)
{
        return __getopt_long(argc, argv, optstring, longopts, idx, 1);
}