1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
/*
* Copyright (c) 2003 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* - Redistribution of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistribution in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
* INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN
* MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR
* ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
* DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE
* DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY,
* ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF
* SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed or intended for use
* in the design, construction, operation or maintenance of any nuclear
* facility.
*
* Sun gratefully acknowledges that this software was originally authored
* and developed by Kenneth Bradley Russell and Christopher John Kline.
*/
package demos.util;
/** Implementation of {@link demos.util.Time} interface based
on {@link java.lang.System.currentTimeMillis}. Performs smoothing
internally to avoid effects of poor granularity of
currentTimeMillis on Windows platform in particular. */
public class SystemTime implements Time {
private static final int DEFAULT_NUM_SMOOTHING_SAMPLES = 10;
private long[] samples = new long[DEFAULT_NUM_SMOOTHING_SAMPLES];
private int numSmoothingSamples;
private int curSmoothingSample; // Index of current sample to be replaced
private long baseTime = System.currentTimeMillis();
private boolean hasCurTime;
private double curTime;
private double deltaT;
/** Sets number of smoothing samples. Defaults to 10. Note that
there may be a discontinuity in the reported time after a call
to this method. */
public void setNumSmoothingSamples(int num) {
samples = new long[num];
numSmoothingSamples = 0;
curSmoothingSample = 0;
hasCurTime = false;
}
/** Returns number of smoothing samples; default is 10. */
public int getNumSmoothingSamples() {
return samples.length;
}
/** Rebases this timer. After very long periods of time the
resolution of this timer may decrease; the application can call
this to restore higher resolution. Note that there may be a
discontinuity in the reported time after a call to this
method. */
public void rebase() {
baseTime = System.currentTimeMillis();
setNumSmoothingSamples(samples.length);
}
public void update() {
long tmpTime = System.currentTimeMillis();
long diffSinceBase = tmpTime - baseTime;
samples[curSmoothingSample] = diffSinceBase;
curSmoothingSample = (curSmoothingSample + 1) % samples.length;
numSmoothingSamples = Math.min(1 + numSmoothingSamples, samples.length);
// Average of samples is current time
double newCurTime = 0.0;
for (int i = 0; i < numSmoothingSamples; i++) {
newCurTime += samples[i];
}
newCurTime /= (1000.0f * numSmoothingSamples);
double lastTime = curTime;
if (!hasCurTime) {
lastTime = newCurTime;
hasCurTime = true;
}
deltaT = newCurTime - lastTime;
curTime = newCurTime;
}
public double time() {
return curTime;
}
public double deltaT() {
return deltaT;
}
}
|
