1 /*
2 * Copyright (C) 2019, Thomas Wolf <thomas.wolf@paranor.ch>
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 package org.eclipse.jgit.treewalk;
44
45 import java.time.Instant;
46 import java.util.Comparator;
47
48 /**
49 * Specialized comparator for {@link Instant}s. If either timestamp has a zero
50 * fraction, compares only seconds. If either timestamp has no time fraction
51 * smaller than a millisecond, compares only milliseconds. If either timestamp
52 * has no fraction smaller than a microsecond, compares only microseconds.
53 */
54 class InstantComparator implements Comparator<Instant> {
55
56 @Override
57 public int compare(Instant a, Instant b) {
58 return compare(a, b, false);
59 }
60
61 /**
62 * Compares two {@link Instant}s to the lower resolution of the two
63 * instants. See {@link InstantComparator}.
64 *
65 * @param a
66 * first {@link Instant} to compare
67 * @param b
68 * second {@link Instant} to compare
69 * @param forceSecondsOnly
70 * whether to omit all fraction comparison
71 * @return a value < 0 if a < b, a value > 0 if a > b, and 0 if
72 * a == b
73 */
74 public int compare(Instant a, Instant b, boolean forceSecondsOnly) {
75 long aSeconds = a.getEpochSecond();
76 long bSeconds = b.getEpochSecond();
77 int result = Long.compare(aSeconds, bSeconds);
78 if (result != 0) {
79 return result;
80 }
81 int aSubSecond = a.getNano();
82 int bSubSecond = b.getNano();
83 if (forceSecondsOnly || (aSubSecond == 0)
84 || (bSubSecond == 0)) {
85 // Don't check the subseconds part.
86 return 0;
87 } else if (aSubSecond != bSubSecond) {
88 // If either has nothing smaller than a millisecond, compare only
89 // milliseconds.
90 int aSubMillis = aSubSecond % 1_000_000;
91 int bSubMillis = bSubSecond % 1_000_000;
92 if (aSubMillis == 0) {
93 bSubSecond -= bSubMillis;
94 } else if (bSubMillis == 0) {
95 aSubSecond -= aSubMillis;
96 } else {
97 // Same again, but for microsecond resolution. NTFS has 100ns
98 // resolution, but WindowsFileAttributes may provide only
99 // microseconds (1000ns). Similar for some Unix file systems.
100 int aSubMicros = aSubSecond % 1000;
101 int bSubMicros = bSubSecond % 1000;
102 if (aSubMicros == 0) {
103 bSubSecond -= bSubMicros;
104 } else if (bSubMicros == 0) {
105 aSubSecond -= aSubMicros;
106 }
107 }
108 }
109 return Integer.compare(aSubSecond, bSubSecond);
110 }
111
112 }