JDK8/Java8源码在线阅读

/*
 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package com.sun.media.sound;

/**
 * A standard transformer used in connection blocks.
 * It expects input values to be between 0 and 1.
 *
 * The result of the transform is
 *   between 0 and 1 if polarity = unipolar and
 *   between -1 and 1 if polarity = bipolar.
 *
 * These constraints only applies to Concave, Convex and Switch transforms.
 *
 * @author Karl Helgason
 */
public final class ModelStandardTransform implements ModelTransform {

    public static final boolean DIRECTION_MIN2MAX = false;
    public static final boolean DIRECTION_MAX2MIN = true;
    public static final boolean POLARITY_UNIPOLAR = false;
    public static final boolean POLARITY_BIPOLAR = true;
    public static final int TRANSFORM_LINEAR = 0;
    // concave: output = (20*log10(127^2/value^2)) / 96
    public static final int TRANSFORM_CONCAVE = 1;
    // convex: same as concave except that start and end point are reversed.
    public static final int TRANSFORM_CONVEX = 2;
    // switch: if value > avg(max,min) then max else min
    public static final int TRANSFORM_SWITCH = 3;
    public static final int TRANSFORM_ABSOLUTE = 4;
    private boolean direction = DIRECTION_MIN2MAX;
    private boolean polarity = POLARITY_UNIPOLAR;
    private int transform = TRANSFORM_LINEAR;

    public ModelStandardTransform() {
    }

    public ModelStandardTransform(boolean direction) {
        this.direction = direction;
    }

    public ModelStandardTransform(boolean direction, boolean polarity) {
        this.direction = direction;
        this.polarity = polarity;
    }

    public ModelStandardTransform(boolean direction, boolean polarity,
            int transform) {
        this.direction = direction;
        this.polarity = polarity;
        this.transform = transform;
    }

    public double transform(double value) {
        double s;
        double a;
        if (direction == DIRECTION_MAX2MIN)
            value = 1.0 - value;
        if (polarity == POLARITY_BIPOLAR)
            value = value * 2.0 - 1.0;
        switch (transform) {
            case TRANSFORM_CONCAVE:
                s = Math.signum(value);
                a = Math.abs(value);
                a = -((5.0 / 12.0) / Math.log(10)) * Math.log(1.0 - a);
                if (a < 0)
                    a = 0;
                else if (a > 1)
                    a = 1;
                return s * a;
            case TRANSFORM_CONVEX:
                s = Math.signum(value);
                a = Math.abs(value);
                a = 1.0 + ((5.0 / 12.0) / Math.log(10)) * Math.log(a);
                if (a < 0)
                    a = 0;
                else if (a > 1)
                    a = 1;
                return s * a;
            case TRANSFORM_SWITCH:
                if (polarity == POLARITY_BIPOLAR)
                    return (value > 0) ? 1 : -1;
                else
                    return (value > 0.5) ? 1 : 0;
            case TRANSFORM_ABSOLUTE:
                return Math.abs(value);
            default:
                break;
        }

        return value;
    }


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