01: //
02: // Copyright (C) 2005 United States Government as represented by the
03: // Administrator of the National Aeronautics and Space Administration
04: // (NASA). All Rights Reserved.
05: //
06: // This software is distributed under the NASA Open Source Agreement
07: // (NOSA), version 1.3. The NOSA has been approved by the Open Source
08: // Initiative. See the file NOSA-1.3-JPF at the top of the distribution
09: // directory tree for the complete NOSA document.
10: //
11: // THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
12: // KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
13: // LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
14: // SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
15: // A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
16: // THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
17: // DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
18: //
19: package gov.nasa.jpf.util;
20:
21: /**
22: * object to compute complex hash values that can be accumulated and
23: * delegated (to aggregates etc.)
24: * used to obtain hashcodes for states
25: */
26: public class HashData {
27: private int poly = 0x88888EEF;
28: private int m = -1;
29:
30: public int getValue() {
31: return (m >>> 4) ^ (m & 15);
32: }
33:
34: public void add(int value) {
35: if (m < 0) {
36: m += m;
37: m ^= poly;
38: } else {
39: m += m;
40: }
41:
42: m ^= value;
43: }
44:
45: public void add(String s) {
46: // probably a bit too simplistic (the Java String hashing isn't stellar)
47: if (s != null) {
48: add(s.hashCode());
49: }
50: }
51:
52: public void add(boolean b) {
53: // a clear case of '42', but that's the "official" boolean hashing
54: add(b ? 1231 : 1237);
55: }
56: }
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