1 /*
2 * Copyright (C) 2016, Google Inc.
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.util.time;
45
46 import static java.util.concurrent.TimeUnit.MICROSECONDS;
47 import static java.util.concurrent.TimeUnit.MILLISECONDS;
48
49 import java.time.Duration;
50 import java.util.concurrent.TimeUnit;
51 import java.util.concurrent.atomic.AtomicLong;
52
53 /**
54 * A {@link MonotonicClock} based on {@code System.currentTimeMillis}.
55 *
56 * @since 4.6
57 */
58 public class MonotonicSystemClock implements MonotonicClock {
59 private static final AtomicLong before = new AtomicLong();
60
61 private static long nowMicros() {
62 long now = MILLISECONDS.toMicros(System.currentTimeMillis());
63 for (;;) {
64 long o = before.get();
65 long n = Math.max(o + 1, now);
66 if (before.compareAndSet(o, n)) {
67 return n;
68 }
69 }
70 }
71
72 @Override
73 public ProposedTimestamp propose() {
74 final long u = nowMicros();
75 return new ProposedTimestamp() {
76 @Override
77 public long read(TimeUnit unit) {
78 return unit.convert(u, MICROSECONDS);
79 }
80
81 @Override
82 public void blockUntil(Duration maxWait) {
83 // Assume system clock never goes backwards.
84 }
85 };
86 }
87 }