ngx_int_t
ngx_hash_add_key(ngx_hash_keys_arrays_t *ha, ngx_str_t *key, void *value,
    ngx_uint_t flags)
{
    size_t           len;
    u_char          *p;
    ngx_str_t       *name;
    ngx_uint_t       i, k, n, skip, last;
    ngx_array_t     *keys, *hwc;
    ngx_hash_key_t  *hk;

    last = key->len;

    if (flags & NGX_HASH_WILDCARD_KEY) {

        /*
         * supported wildcards:
         *     "*.example.com", ".example.com", and "www.example.*"
         */

        n = 0;

        for (i = 0; i < key->len; i++) {

            if (key->data[i] == '*') {
                if (++n > 1) {
                    return NGX_DECLINED;
                }
            }

            if (key->data[i] == '.' && key->data[i + 1] == '.') {
                return NGX_DECLINED;
            }
        }

        if (key->len > 1 && key->data[0] == '.') {
            skip = 1;
            goto wildcard;
        }

        if (key->len > 2) {

            if (key->data[0] == '*' && key->data[1] == '.') {
                skip = 2;
                goto wildcard;
            }

            if (key->data[i - 2] == '.' && key->data[i - 1] == '*') {
                skip = 0;
                last -= 2;
                goto wildcard;
            }
        }

        if (n) {
            return NGX_DECLINED;
        }
    }

    /* exact hash */

    k = 0;

    for (i = 0; i < last; i++) {
        if (!(flags & NGX_HASH_READONLY_KEY)) {
            key->data[i] = ngx_tolower(key->data[i]);
        }
        k = ngx_hash(k, key->data[i]);
    }

    k %= ha->hsize;

    /* check conflicts in exact hash */

    name = ha->keys_hash[k].elts;

    if (name) {
        for (i = 0; i < ha->keys_hash[k].nelts; i++) {
            if (last != name[i].len) {
                continue;
            }

            if (ngx_strncmp(key->data, name[i].data, last) == 0) {
                return NGX_BUSY;
            }
        }

    } else {
        if (ngx_array_init(&ha->keys_hash[k], ha->temp_pool, 4,
                           sizeof(ngx_str_t))
            != NGX_OK)
        {
            return NGX_ERROR;
        }
    }

    name = ngx_array_push(&ha->keys_hash[k]);
    if (name == NULL) {
        return NGX_ERROR;
    }

    *name = *key;

    hk = ngx_array_push(&ha->keys);
    if (hk == NULL) {
        return NGX_ERROR;
    }

    hk->key = *key;
    hk->key_hash = ngx_hash_key(key->data, last);
    hk->value = value;

    return NGX_OK;


wildcard:

    /* wildcard hash */

    k = ngx_hash_strlow(&key->data[skip], &key->data[skip], last - skip);

    k %= ha->hsize;

    if (skip == 1) {

        /* check conflicts in exact hash for ".example.com" */

        name = ha->keys_hash[k].elts;

        if (name) {
            len = last - skip;

            for (i = 0; i < ha->keys_hash[k].nelts; i++) {
                if (len != name[i].len) {
                    continue;
                }

                if (ngx_strncmp(&key->data[1], name[i].data, len) == 0) {
                    return NGX_BUSY;
                }
            }

        } else {
            if (ngx_array_init(&ha->keys_hash[k], ha->temp_pool, 4,
                               sizeof(ngx_str_t))
                != NGX_OK)
            {
                return NGX_ERROR;
            }
        }

        name = ngx_array_push(&ha->keys_hash[k]);
        if (name == NULL) {
            return NGX_ERROR;
        }

        name->len = last - 1;
        name->data = ngx_pnalloc(ha->temp_pool, name->len);
        if (name->data == NULL) {
            return NGX_ERROR;
        }

        ngx_memcpy(name->data, &key->data[1], name->len);
    }


    if (skip) {

        /*
         * convert "*.example.com" to "com.example.\0"
         *      and ".example.com" to "com.example\0"
         */

        p = ngx_pnalloc(ha->temp_pool, last);
        if (p == NULL) {
            return NGX_ERROR;
        }

        len = 0;
        n = 0;

        for (i = last - 1; i; i--) {
            if (key->data[i] == '.') {
                ngx_memcpy(&p[n], &key->data[i + 1], len);
                n += len;
                p[n++] = '.';
                len = 0;
                continue;
            }

            len++;
        }

        if (len) {
            ngx_memcpy(&p[n], &key->data[1], len);
            n += len;
        }

        p[n] = '\0';

        hwc = &ha->dns_wc_head;
        keys = &ha->dns_wc_head_hash[k];

    } else {

        /* convert "www.example.*" to "www.example\0" */

        last++;

        p = ngx_pnalloc(ha->temp_pool, last);
        if (p == NULL) {
            return NGX_ERROR;
        }

        ngx_cpystrn(p, key->data, last);

        hwc = &ha->dns_wc_tail;
        keys = &ha->dns_wc_tail_hash[k];
    }


    /* check conflicts in wildcard hash */

    name = keys->elts;

    if (name) {
        len = last - skip;

        for (i = 0; i < keys->nelts; i++) {
            if (len != name[i].len) {
                continue;
            }

            if (ngx_strncmp(key->data + skip, name[i].data, len) == 0) {
                return NGX_BUSY;
            }
        }

    } else {
        if (ngx_array_init(keys, ha->temp_pool, 4, sizeof(ngx_str_t)) != NGX_OK)
        {
            return NGX_ERROR;
        }
    }

    name = ngx_array_push(keys);
    if (name == NULL) {
        return NGX_ERROR;
    }

    name->len = last - skip;
    name->data = ngx_pnalloc(ha->temp_pool, name->len);
    if (name->data == NULL) {
        return NGX_ERROR;
    }

    ngx_memcpy(name->data, key->data + skip, name->len);


    /* add to wildcard hash */

    hk = ngx_array_push(hwc);
    if (hk == NULL) {
        return NGX_ERROR;
    }

    hk->key.len = last - 1;
    hk->key.data = p;
    hk->key_hash = 0;
    hk->value = value;

    return NGX_OK;
}