001: /*
002: * $RCSfile: HashCodeUtil.java,v $
003: *
004: * Copyright (c) 2007 Sun Microsystems, Inc. All rights reserved.
005: *
006: * Redistribution and use in source and binary forms, with or without
007: * modification, are permitted provided that the following conditions
008: * are met:
009: *
010: * - Redistribution of source code must retain the above copyright
011: * notice, this list of conditions and the following disclaimer.
012: *
013: * - Redistribution in binary form must reproduce the above copyright
014: * notice, this list of conditions and the following disclaimer in
015: * the documentation and/or other materials provided with the
016: * distribution.
017: *
018: * Neither the name of Sun Microsystems, Inc. or the names of
019: * contributors may be used to endorse or promote products derived
020: * from this software without specific prior written permission.
021: *
022: * This software is provided "AS IS," without a warranty of any
023: * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
024: * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
025: * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
026: * EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
027: * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
028: * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
029: * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
030: * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
031: * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
032: * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
033: * INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
034: * POSSIBILITY OF SUCH DAMAGES.
035: *
036: * You acknowledge that this software is not designed, licensed or
037: * intended for use in the design, construction, operation or
038: * maintenance of any nuclear facility.
039: *
040: * $Revision: 1.4 $
041: * $Date: 2007/02/09 17:20:05 $
042: * $State: Exp $
043: */
044:
045: package com.sun.j3d.internal;
046:
047: /**
048: * Utility class used when computing the hash code for
049: * objects containing float or double values. This fixes Issue 36.
050: */
051: public class HashCodeUtil {
052: /**
053: * Returns the representation of the specified floating-point
054: * value according to the IEEE 754 floating-point "single format"
055: * bit layout, after first mapping -0.0 to 0.0. This method is
056: * identical to Float.floatToIntBits(float) except that an integer
057: * value of 0 is returned for a floating-point value of
058: * -0.0f. This is done for the purpose of computing a hash code
059: * that satisfies the contract of hashCode() and equals(). The
060: * equals() method in some Java 3D classes does a pair-wise
061: * "==" test on each floating-point field in the class. Since
062: * 0.0f == -0.0f returns true, we must also return the
063: * same hash code for two objects, one of which has a field with a
064: * value of -0.0f and the other of which has a cooresponding field
065: * with a value of 0.0f.
066: *
067: * @param f an input floating-point number
068: * @return the integer bits representing that floating-point
069: * number, after first mapping -0.0f to 0.0f
070: */
071: public static int floatToIntBits(float f) {
072: // Check for +0 or -0
073: if (f == 0.0f) {
074: return 0;
075: } else {
076: return Float.floatToIntBits(f);
077: }
078: }
079:
080: /**
081: * Returns the representation of the specified floating-point
082: * value according to the IEEE 754 floating-point "double format"
083: * bit layout, after first mapping -0.0 to 0.0. This method is
084: * identical to Double.doubleToLongBits(double) except that an
085: * integer value of 0L is returned for a floating-point value of
086: * -0.0. This is done for the purpose of computing a hash code
087: * that satisfies the contract of hashCode() and equals(). The
088: * equals() method in some Java 3D classes does a pair-wise
089: * "==" test on each floating-point field in the class. Since
090: * 0.0 == -0.0 returns true, we must also return the
091: * same hash code for two objects, one of which has a field with a
092: * value of -0.0 and the other of which has a cooresponding field
093: * with a value of 0.0.
094: *
095: * @param d an input double precision floating-point number
096: * @return the integer bits representing that floating-point
097: * number, after first mapping -0.0f to 0.0f
098: */
099: public static long doubleToLongBits(double d) {
100: // Check for +0 or -0
101: if (d == 0.0) {
102: return 0L;
103: } else {
104: return Double.doubleToLongBits(d);
105: }
106: }
107:
108: /**
109: * Do not construct an instance of this class.
110: */
111: private HashCodeUtil() {
112: }
113: }
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