source: azure_iot_hub/trunk/musl-1.1.18/src/network/gethostbyname2_r.c@ 388

#define _GNU_SOURCE

#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <netinet/in.h>
#include <errno.h>
#include <stdint.h>
#include "lookup.h"

int gethostbyname2_r(const char *name, int af,
        struct hostent *h, char *buf, size_t buflen,
        struct hostent **res, int *err)
{
        struct address addrs[MAXADDRS];
        char canon[256];
        int i, cnt;
        size_t align, need;

        *res = 0;
        cnt = __lookup_name(addrs, canon, name, af, AI_CANONNAME);
        if (cnt<0) switch (cnt) {
        case EAI_NONAME:
                *err = HOST_NOT_FOUND;
                return ENOENT;
        case EAI_AGAIN:
                *err = TRY_AGAIN;
                return EAGAIN;
        default:
        case EAI_FAIL:
                *err = NO_RECOVERY;
                return EBADMSG;
        case EAI_MEMORY:
        case EAI_SYSTEM:
                *err = NO_RECOVERY;
                return errno;
        }

        h->h_addrtype = af;
        h->h_length = af==AF_INET6 ? 16 : 4;

        /* Align buffer */
        align = -(uintptr_t)buf & sizeof(char *)-1;

        need = 4*sizeof(char *);
        need += (cnt + 1) * (sizeof(char *) + h->h_length);
        need += strlen(name)+1;
        need += strlen(canon)+1;
        need += align;

        if (need > buflen) return ERANGE;

        buf += align;
        h->h_aliases = (void *)buf;
        buf += 3*sizeof(char *);
        h->h_addr_list = (void *)buf;
        buf += (cnt+1)*sizeof(char *);

        for (i=0; i<cnt; i++) {
                h->h_addr_list[i] = (void *)buf;
                buf += h->h_length;
                memcpy(h->h_addr_list[i], addrs[i].addr, h->h_length);
        }
        h->h_addr_list[i] = 0;

        h->h_name = h->h_aliases[0] = buf;
        strcpy(h->h_name, canon);
        buf += strlen(h->h_name)+1;

        if (strcmp(h->h_name, name)) {
                h->h_aliases[1] = buf;
                strcpy(h->h_aliases[1], name);
                buf += strlen(h->h_aliases[1])+1;
        } else h->h_aliases[1] = 0;

        h->h_aliases[2] = 0;

        *res = h;
        return 0;
}