/*
 * $RCSfile$
 *
 * Copyright (c) 2007 Sun Microsystems, Inc. All rights reserved.
 *
 * Use is subject to license terms.
 *
 * $Revision$
 * $Date$
 * $State$
 */

package javax.vecmath;

/**
 * Utility vecmath class used when computing the hash code for vecmath
 * objects containing float or double values. This fixes Issue 36.
 */
class VecMathUtil {
    /**
     * 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 each vecmath class does a pair-wise "=="
     * test on each floating-point field in the class (e.g., x, y, and
     * z for a Tuple3f). 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
     */
    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 each vecmath class does a pair-wise "=="
     * test on each floating-point field in the class (e.g., x, y, and
     * z for a Tuple3d). 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
     */
    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 VecMathUtil() {
    }
}