#define _GNU_SOURCE
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int
main(int argc, char *argv[])
{
    int i, ret;
    struct gaicb *reqs[argc − 1];
    char host[NI_MAXHOST];
    struct addrinfo *res;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s HOST...\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    for (i = 0; i < argc − 1; i++) {
        reqs[i] = malloc(sizeof(*reqs[0]));
        if (reqs[i] == NULL) {
            perror("malloc");
            exit(EXIT_FAILURE);
        }
        memset(reqs[i], 0, sizeof(*reqs[0]));
        reqs[i]−>ar_name = argv[i + 1];
    }

    ret = getaddrinfo_a(GAI_WAIT, reqs, argc − 1, NULL);
    if (ret != 0) {
        fprintf(stderr, "getaddrinfo_a() failed: %s\n",
                gai_strerror(ret));
        exit(EXIT_FAILURE);
    }

    for (i = 0; i < argc − 1; i++) {
        printf("%s: ", reqs[i]−>ar_name);
        ret = gai_error(reqs[i]);
        if (ret == 0) {
            res = reqs[i]−>ar_result;

            ret = getnameinfo(res−>ai_addr, res−>ai_addrlen,
                    host, sizeof(host),
                    NULL, 0, NI_NUMERICHOST);
            if (ret != 0) {
                fprintf(stderr, "getnameinfo() failed: %s\n",
                        gai_strerror(ret));
                exit(EXIT_FAILURE);
            }
            puts(host);

        } else {
            puts(gai_strerror(ret));
        }
    }
    exit(EXIT_SUCCESS);
}

#define _GNU_SOURCE
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static struct gaicb **reqs = NULL;
static int nreqs = 0;

static char *
getcmd(void)
{
    static char buf[256];

    fputs("> ", stdout); fflush(stdout);
    if (fgets(buf, sizeof(buf), stdin) == NULL)
        return NULL;

    if (buf[strlen(buf) − 1] == '\n')
        buf[strlen(buf) − 1] = 0;

    return buf;
}

/* Add requests for specified hostnames */
static void
add_requests(void)
{
    int nreqs_base = nreqs;
    char *host;
    int ret;

    while ((host = strtok(NULL, " "))) {
        nreqs++;
        reqs = realloc(reqs, nreqs * sizeof(reqs[0]));

        reqs[nreqs − 1] = calloc(1, sizeof(*reqs[0]));
        reqs[nreqs − 1]−>ar_name = strdup(host);
    }

    /* Queue nreqs_base..nreqs requests. */

    ret = getaddrinfo_a(GAI_NOWAIT, &reqs[nreqs_base],
                        nreqs − nreqs_base, NULL);
    if (ret) {
        fprintf(stderr, "getaddrinfo_a() failed: %s\n",
                gai_strerror(ret));
        exit(EXIT_FAILURE);
    }
}

/* Wait until at least one of specified requests completes */
static void
wait_requests(void)
{
    char *id;
    int i, ret, n;
    struct gaicb const **wait_reqs = calloc(nreqs, sizeof(*wait_reqs));
                /* NULL elements are ignored by gai_suspend(). */

    while ((id = strtok(NULL, " ")) != NULL) {
        n = atoi(id);

        if (n >= nreqs) {
            printf("Bad request number: %s\n", id);
            return;
        }

        wait_reqs[n] = reqs[n];
    }

    ret = gai_suspend(wait_reqs, nreqs, NULL);
    if (ret) {
        printf("gai_suspend(): %s\n", gai_strerror(ret));
        return;
    }

    for (i = 0; i < nreqs; i++) {
        if (wait_reqs[i] == NULL)
            continue;

        ret = gai_error(reqs[i]);
        if (ret == EAI_INPROGRESS)
            continue;

        printf("[%02d] %s: %s\n", i, reqs[i]−>ar_name,
               ret == 0 ? "Finished" : gai_strerror(ret));
    }
}

/* Cancel specified requests */
static void
cancel_requests(void)
{
    char *id;
    int ret, n;

    while ((id = strtok(NULL, " ")) != NULL) {
        n = atoi(id);

        if (n >= nreqs) {
            printf("Bad request number: %s\n", id);
            return;
        }

        ret = gai_cancel(reqs[n]);
        printf("[%s] %s: %s\n", id, reqs[atoi(id)]−>ar_name,
               gai_strerror(ret));
    }
}

/* List all requests */
static void
list_requests(void)
{
    int i, ret;
    char host[NI_MAXHOST];
    struct addrinfo *res;

    for (i = 0; i < nreqs; i++) {
        printf("[%02d] %s: ", i, reqs[i]−>ar_name);
        ret = gai_error(reqs[i]);

        if (!ret) {
            res = reqs[i]−>ar_result;

            ret = getnameinfo(res−>ai_addr, res−>ai_addrlen,
                              host, sizeof(host),
                              NULL, 0, NI_NUMERICHOST);
            if (ret) {
                fprintf(stderr, "getnameinfo() failed: %s\n",
                        gai_strerror(ret));
                exit(EXIT_FAILURE);
            }
            puts(host);
        } else {
            puts(gai_strerror(ret));
        }
    }
}

int
main(int argc, char *argv[])
{
    char *cmdline;
    char *cmd;

    while ((cmdline = getcmd()) != NULL) {
        cmd = strtok(cmdline, " ");

        if (cmd == NULL) {
            list_requests();
        } else {
            switch (cmd[0]) {
            case 'a':
                add_requests();
                break;
            case 'w':
                wait_requests();
                break;
            case 'c':
                cancel_requests();
                break;
            case 'l':
                list_requests();
                break;
            default:
                fprintf(stderr, "Bad command: %c\n", cmd[0]);
                break;
            }
        }
    }
    exit(EXIT_SUCCESS);
}