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   * Copyright 2012-2015, Inc. or its affiliates. All Rights Reserved.
   * Licensed under the Apache License, Version 2.0 (the "License").
   * You may not use this file except in compliance with the License.
   * A copy of the License is located at
  * or in the "license" file accompanying this file. This file is distributed
  * express or implied. See the License for the specific language governing
  * permissions and limitations under the License.
 package com.amazonaws.util;
 public class AwsHostNameUtils {
     private static final Pattern S3_ENDPOINT_PATTERN =
     private static final Pattern STANDARD_CLOUDSEARCH_ENDPOINT_PATTERN =
     private static final Pattern EXTENDED_CLOUDSEARCH_ENDPOINT_PATTERN =

     public static String parseRegionName(URI endpoint) {
         return parseRegionName(endpoint.getHost(), null);

Attempts to parse the region name from an endpoint based on conventions about the endpoint format.

host the hostname to parse
serviceHint an optional hint about the service for the endpoint
the region parsed from the hostname, or "us-east-1" if no region information could be found
     public static String parseRegionName(final String host,
                                          final String serviceHint) {
         String regionNameInInternalConfig = parseRegionNameByInternalConfig(host);
         if (regionNameInInternalConfig != null) {
             return regionNameInInternalConfig;
         if (host.endsWith("")) {
             int index = host.length() - "".length();
             return parseStandardRegionName(host.substring(0, index));
         if (serviceHint != null) {
             if (serviceHint.equals("cloudsearch")
                     && !host.startsWith("cloudsearch.")) {
                 // CloudSearch domains use the nonstandard domain format
                 // [domain].[region].cloudsearch.[suffix].
                 Matcher matcher = 
                 if (matcher.matches()) {
             // If we have a service hint, look for 'service.[region]' or
             // 'service-[region]' in the endpoint's hostname.
             Pattern pattern = Pattern.compile(
                 + Pattern.quote(serviceHint)
                 + "[.-]([a-z0-9-]+)\\."
             Matcher matcher = pattern.matcher(host);
             if (matcher.find()) {
         // Endpoint is totally non-standard; guess us-east-1 for lack of a
         // better option.
        return "us-east-1";

Parses the region name from a standard (* endpoint.

fragment the portion of the endpoint excluding ""
the parsed region name (or "us-east-1" as a best guess if we can't tell for sure)
    private static String parseStandardRegionName(final String fragment) {
        Matcher matcher = .matcher(fragment);
        if (matcher.matches()) {
            // host was 'bucket.s3-[region]'.
        matcher = .matcher(fragment);
        if (matcher.matches()) {
            // host was 'domain.[region]'.
        int index = fragment.lastIndexOf('.');
        if (index == -1) {
            // host was '', guess us-east-1
            // for lack of a better option.
            return "us-east-1";
        // host was 'service.[region]'.
        String region = fragment.substring(index + 1);
        // Special case for, which is actually
        // us-gov-west-1.
        if ("us-gov".equals(region)) {
            region = "us-gov-west-1";
        return region;


the configured region name if the given host name matches any of the host-to-region mappings in the internal config; otherwise return null.
    private static String parseRegionNameByInternalConfig(String host) {
        InternalConfig internConfig = InternalConfig.Factory.getInternalConfig();
        for (HostRegexToRegionMapping mapping : internConfig.getHostRegexToRegionMappings()) {
            String hostNameRegex = mapping.getHostNameRegex();
            if (host.matches(hostNameRegex)) {
                return mapping.getRegionName();
        return null;

Parses the service name from an endpoint. Can only handle endpoints of the form 'service.[region.]'.
    public static String parseServiceName(URI endpoint) {
        String host = endpoint.getHost();
        // If we don't recognize the domain, throw an exception.
        if (!host.endsWith("")) {
            throw new IllegalArgumentException(
                "Cannot parse a service name from an unrecognized endpoint ("
                + host
                + ").");
        String serviceAndRegion =
            host.substring(0, host.indexOf(""));
        // Special cases for S3 endpoints with bucket names embedded.
        if (serviceAndRegion.endsWith(".s3")
            || .matcher(serviceAndRegion).matches()) {
            return "s3";
        char separator = '.';
        // If we don't detect a separator between service name and region, then
        // assume that the region is not included in the hostname, and it's only
        // the service name (ex: "").
        if (serviceAndRegion.indexOf(separator) == -1) {
            return serviceAndRegion;
        String service =
            serviceAndRegion.substring(0, serviceAndRegion.indexOf(separator));
        return service;

Returns the host name for the local host. If the operation is not allowed by the security check, the textual representation of the IP address of the local host is returned instead. If the ip address of the local host cannot be resolved or if there is any other failure, "localhost" is returned as a fallback.
    public static String localHostName() {
        try {
            InetAddress localhost = InetAddress.getLocalHost();
            return localhost.getHostName();
        } catch (Exception e) {
                    "Failed to determine the local hostname; fall back to "
                            + "use \"localhost\"."e);
            return "localhost";
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