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.sql.Timestamp;
50 import java.time.Duration;
51 import java.time.Instant;
52 import java.util.Date;
53 import java.util.Iterator;
54 import java.util.concurrent.TimeUnit;
55 import java.util.concurrent.TimeoutException;
56
57 /**
58 * A timestamp generated by
59 * {@link org.eclipse.jgit.util.time.MonotonicClock#propose()}.
60 * <p>
61 * ProposedTimestamp implements AutoCloseable so that implementations can
62 * release resources associated with obtaining certainty about time elapsing.
63 * For example the constructing MonotonicClock may start network IO with peers
64 * when creating the ProposedTimestamp, and {@link #close()} can ensure those
65 * network resources are released in a timely fashion.
66 *
67 * @since 4.6
68 */
69 public abstract class ProposedTimestamp implements AutoCloseable {
70 /**
71 * Wait for several timestamps.
72 *
73 * @param times
74 * timestamps to wait on.
75 * @param maxWait
76 * how long to wait for the timestamps.
77 * @throws java.lang.InterruptedException
78 * current thread was interrupted before the waiting process
79 * completed normally.
80 * @throws java.util.concurrent.TimeoutException
81 * the timeout was reached without the proposed timestamp become
82 * certainly in the past.
83 */
84 public static void blockUntil(Iterable<ProposedTimestamp> times,
85 Duration maxWait) throws TimeoutException, InterruptedException {
86 Iterator<ProposedTimestamp> itr = times.iterator();
87 if (!itr.hasNext()) {
88 return;
89 }
90
91 long now = System.currentTimeMillis();
92 long deadline = now + maxWait.toMillis();
93 for (;;) {
94 long w = deadline - now;
95 if (w < 0) {
96 throw new TimeoutException();
97 }
98 itr.next().blockUntil(Duration.ofMillis(w));
99 if (itr.hasNext()) {
100 now = System.currentTimeMillis();
101 } else {
102 break;
103 }
104 }
105 }
106
107 /**
108 * Read the timestamp as {@code unit} since the epoch.
109 * <p>
110 * The timestamp value for a specific {@code ProposedTimestamp} object never
111 * changes, and can be read before {@link #blockUntil(Duration)}.
112 *
113 * @param unit
114 * what unit to return the timestamp in. The timestamp will be
115 * rounded if the unit is bigger than the clock's granularity.
116 * @return {@code unit} since the epoch.
117 */
118 public abstract long read(TimeUnit unit);
119
120 /**
121 * Wait for this proposed timestamp to be certainly in the recent past.
122 * <p>
123 * This method forces the caller to wait up to {@code timeout} for
124 * {@code this} to pass sufficiently into the past such that the creating
125 * {@link org.eclipse.jgit.util.time.MonotonicClock} instance will not
126 * create an earlier timestamp.
127 *
128 * @param maxWait
129 * how long the implementation may block the caller.
130 * @throws java.lang.InterruptedException
131 * current thread was interrupted before the waiting process
132 * completed normally.
133 * @throws java.util.concurrent.TimeoutException
134 * the timeout was reached without the proposed timestamp
135 * becoming certainly in the past.
136 */
137 public abstract void blockUntil(Duration maxWait)
138 throws InterruptedException, TimeoutException;
139
140 /**
141 * Get milliseconds since epoch; {@code read(MILLISECONDS}).
142 *
143 * @return milliseconds since epoch; {@code read(MILLISECONDS}).
144 */
145 public long millis() {
146 return read(MILLISECONDS);
147 }
148
149 /**
150 * Get microseconds since epoch; {@code read(MICROSECONDS}).
151 *
152 * @return microseconds since epoch; {@code read(MICROSECONDS}).
153 */
154 public long micros() {
155 return read(MICROSECONDS);
156 }
157
158 /**
159 * Get time since epoch, with up to microsecond resolution.
160 *
161 * @return time since epoch, with up to microsecond resolution.
162 */
163 public Instant instant() {
164 long usec = micros();
165 long secs = usec / 1000000L;
166 long nanos = (usec % 1000000L) * 1000L;
167 return Instant.ofEpochSecond(secs, nanos);
168 }
169
170 /**
171 * Get time since epoch, with up to microsecond resolution.
172 *
173 * @return time since epoch, with up to microsecond resolution.
174 */
175 public Timestamp timestamp() {
176 return Timestamp.from(instant());
177 }
178
179 /**
180 * Get time since epoch, with up to millisecond resolution.
181 *
182 * @return time since epoch, with up to millisecond resolution.
183 */
184 public Date date() {
185 return new Date(millis());
186 }
187
188 /**
189 * {@inheritDoc}
190 * <p>
191 * Release resources allocated by this timestamp.
192 */
193 @Override
194 public void close() {
195 // Do nothing by default.
196 }
197
198 /** {@inheritDoc} */
199 @Override
200 public String toString() {
201 return instant().toString();
202 }
203 }