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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
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 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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package sun.security.ssl;

import javax.net.ssl.*;
import java.util.*;
import sun.net.util.IPAddressUtil;

A utility class to share the static methods.
/**
 * A utility class to share the static methods.
 */
final class Utilities {
    
hex digits
/**
     * hex digits
     */
    static final char[] hexDigits = "0123456789ABCDEF".toCharArray();

    
Puts hostname into the serverNames list. 
 If the serverNames does not look like a legal FQDN, it will not be put into the returned list. 

Note that the returned list does not allow duplicated name type.
Returns:
a list of SNIServerName/**
     * Puts {@code hostname} into the {@code serverNames} list.
     * <P>
     * If the {@code serverNames} does not look like a legal FQDN, it will
     * not be put into the returned list.
     * <P>
     * Note that the returned list does not allow duplicated name type.
     *
     * @return a list of {@link SNIServerName}
     */
    static List<SNIServerName> addToSNIServerNameList(
            List<SNIServerName> serverNames, String hostname) {

        SNIHostName sniHostName = rawToSNIHostName(hostname);
        if (sniHostName == null) {
            return serverNames;
        }

        int size = serverNames.size();
        List<SNIServerName> sniList = (size != 0) ?
                new ArrayList<SNIServerName>(serverNames) :
                new ArrayList<SNIServerName>(1);

        boolean reset = false;
        for (int i = 0; i < size; i++) {
            SNIServerName serverName = sniList.get(i);
            if (serverName.getType() == StandardConstants.SNI_HOST_NAME) {
                sniList.set(i, sniHostName);
                if (Debug.isOn("ssl")) {
                    System.out.println(Thread.currentThread().getName() +
                        ", the previous server name in SNI (" + serverName +
                        ") was replaced with (" + sniHostName + ")");
                }
                reset = true;
                break;
            }
        }

        if (!reset) {
            sniList.add(sniHostName);
        }

        return Collections.<SNIServerName>unmodifiableList(sniList);
    }

    
Converts string hostname to SNIHostName. 

Note that to check whether a hostname is a valid domain name, we cannot
use the hostname resolved from name services.  For virtual hosting,
multiple hostnames may be bound to the same IP address, so the hostname
resolved from name services is not always reliable.
Params:
hostname – 
        the raw hostname
Returns:
an instance of SNIHostName, or null if the hostname does not look like a FQDN/**
     * Converts string hostname to {@code SNIHostName}.
     * <P>
     * Note that to check whether a hostname is a valid domain name, we cannot
     * use the hostname resolved from name services.  For virtual hosting,
     * multiple hostnames may be bound to the same IP address, so the hostname
     * resolved from name services is not always reliable.
     *
     * @param  hostname
     *         the raw hostname
     * @return an instance of {@link SNIHostName}, or null if the hostname does
     *         not look like a FQDN
     */
    private static SNIHostName rawToSNIHostName(String hostname) {
        SNIHostName sniHostName = null;
        if (hostname != null && hostname.indexOf('.') > 0 &&
                !hostname.endsWith(".") &&
                !IPAddressUtil.isIPv4LiteralAddress(hostname) &&
                !IPAddressUtil.isIPv6LiteralAddress(hostname)) {

            try {
                sniHostName = new SNIHostName(hostname);
            } catch (IllegalArgumentException iae) {
                // don't bother to handle illegal host_name
                if (Debug.isOn("ssl")) {
                    System.out.println(Thread.currentThread().getName() +
                        ", \"" + hostname + "\" " +
                        "is not a legal HostName for  server name indication");
                }
            }
        }

        return sniHostName;
    }
}