1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.hc.client5.http.impl.cache;
28
29 import java.net.InetAddress;
30 import java.net.UnknownHostException;
31 import java.security.NoSuchAlgorithmException;
32 import java.security.SecureRandom;
33 import java.util.Formatter;
34 import java.util.Locale;
35 import java.util.concurrent.locks.ReentrantLock;
36
37 /**
38 * Should produce reasonably unique tokens.
39 */
40 class BasicIdGenerator {
41
42 private final String hostname;
43 private final SecureRandom rnd;
44
45 private long count;
46
47 private final ReentrantLock lock;
48
49 public BasicIdGenerator() {
50 super();
51 String hostname;
52 try {
53 hostname = InetAddress.getLocalHost().getHostName();
54 } catch (final UnknownHostException ex) {
55 hostname = "localhost";
56 }
57 this.hostname = hostname;
58 try {
59 this.rnd = SecureRandom.getInstance("SHA1PRNG");
60 } catch (final NoSuchAlgorithmException ex) {
61 throw new Error(ex);
62 }
63 this.rnd.setSeed(System.currentTimeMillis());
64 this.lock = new ReentrantLock();
65 }
66
67 public void generate(final StringBuilder buffer) {
68 lock.lock();
69 try {
70 this.count++;
71 final int rndnum = this.rnd.nextInt();
72 buffer.append(System.currentTimeMillis());
73 buffer.append('.');
74 try (Formatter formatter = new Formatter(buffer, Locale.ROOT)) {
75 formatter.format("%1$016x-%2$08x", this.count, rndnum);
76 }
77 buffer.append('.');
78 buffer.append(this.hostname);
79 } finally {
80 lock.unlock();
81 }
82 }
83
84 public String generate() {
85 final StringBuilder buffer = new StringBuilder();
86 generate(buffer);
87 return buffer.toString();
88 }
89
90 }