Issue number: 36

Submitted by:  kcr
Fixed Issue 36 -- Vector3d hashCode() method distinguishes between -0.0 and 0.0


git-svn-id: https://svn.java.net/svn/j3d-core-utils~svn/trunk@23 9497e636-51bd-65ba-982d-a4982e1767a5

1 files changed, 116 insertions, 0 deletions

diff --git a/src/classes/share/com/sun/j3d/internal/HashCodeUtil.java b/src/classes/share/com/sun/j3d/internal/HashCodeUtil.java
new file mode 100644
index 0000000..7d14b60
--- /dev/null
+++ b/src/classes/share/com/sun/j3d/internal/HashCodeUtil.java
@@ -0,0 +1,116 @@
+/*
+ * $RCSfile$
+ *
+ * Copyright (c) 2004 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, licensed or
+ * intended for use in the design, construction, operation or
+ * maintenance of any nuclear facility.
+ *
+ * $Revision$
+ * $Date$
+ * $State$
+ */
+
+package com.sun.j3d.internal;
+
+/**
+ * Utility class used when computing the hash code for
+ * objects containing float or double values. This fixes Issue 36.
+ */
+public class HashCodeUtil {
+    /**
+     * Returns the representation of the specified floating-point
+     * value according to the IEEE 754 floating-point "single format"
+     * bit layout, after first mapping -0.0 to 0.0. This method is
+     * identical to Float.floatToIntBits(float) except that an integer
+     * value of 0 is returned for a floating-point value of
+     * -0.0f. This is done for the purpose of computing a hash code
+     * that satisfies the contract of hashCode() and equals(). The
+     * equals() method in some Java 3D classes does a pair-wise
+     * "==" test on each floating-point field in the class. Since
+     * 0.0f == -0.0f returns true, we must also return the
+     * same hash code for two objects, one of which has a field with a
+     * value of -0.0f and the other of which has a cooresponding field
+     * with a value of 0.0f.
+     *
+     * @param f an input floating-point number
+     * @return the integer bits representing that floating-point
+     * number, after first mapping -0.0f to 0.0f
+     */
+    public static int floatToIntBits(float f) {
+	// Check for +0 or -0
+	if (f == 0.0f) {
+	    return 0;
+	}
+	else {
+	    return Float.floatToIntBits(f);
+	}
+    }
+
+    /**
+     * Returns the representation of the specified floating-point
+     * value according to the IEEE 754 floating-point "double format"
+     * bit layout, after first mapping -0.0 to 0.0. This method is
+     * identical to Double.doubleToLongBits(double) except that an
+     * integer value of 0L is returned for a floating-point value of
+     * -0.0. This is done for the purpose of computing a hash code
+     * that satisfies the contract of hashCode() and equals(). The
+     * equals() method in some Java 3D classes does a pair-wise
+     * "==" test on each floating-point field in the class. Since
+     * 0.0 == -0.0 returns true, we must also return the
+     * same hash code for two objects, one of which has a field with a
+     * value of -0.0 and the other of which has a cooresponding field
+     * with a value of 0.0.
+     *
+     * @param d an input double precision floating-point number
+     * @return the integer bits representing that floating-point
+     * number, after first mapping -0.0f to 0.0f
+     */
+    public static long doubleToLongBits(double d) {
+	// Check for +0 or -0
+	if (d == 0.0) {
+	    return 0L;
+	}
+	else {
+	    return Double.doubleToLongBits(d);
+	}
+    }
+
+
+    /**
+     * Do not construct an instance of this class.
+     */
+    private HashCodeUtil() {
+    }
+}