JDK8/Java8源码在线阅读

/*
 * Copyright (c) 1999, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.media.sound;

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;

/**
 * Common conversions etc.
 *
 * @author Kara Kytle
 * @author Florian Bomers
 */
public final class Toolkit {

    /**
     * Suppresses default constructor, ensuring non-instantiability.
     */
    private Toolkit() {
    }

    /**
     * Converts bytes from signed to unsigned.
     */
    static void getUnsigned8(byte[] b, int off, int len) {
        for (int i = off; i < (off+len); i++) {
            b[i] += 128;
        }
    }


    /**
     * Swaps bytes.
     * @throws ArrayOutOfBoundsException if len is not a multiple of 2.
     */
    static void getByteSwapped(byte[] b, int off, int len) {

        byte tempByte;
        for (int i = off; i < (off+len); i+=2) {

            tempByte = b[i];
            b[i] = b[i+1];
            b[i+1] = tempByte;
        }
    }


    /**
     * Linear to DB scale conversion.
     */
    static float linearToDB(float linear) {

        float dB = (float) (Math.log((double)((linear==0.0)?0.0001:linear))/Math.log(10.0) * 20.0);
        return dB;
    }


    /**
     * DB to linear scale conversion.
     */
    static float dBToLinear(float dB) {

        float linear = (float) Math.pow(10.0, dB/20.0);
        return linear;
    }

    /*
     * returns bytes aligned to a multiple of blocksize
     * the return value will be in the range of (bytes-blocksize+1) ... bytes
     */
    static long align(long bytes, int blockSize) {
        // prevent null pointers
        if (blockSize <= 1) {
            return bytes;
        }
        return bytes - (bytes % blockSize);
    }

    static int align(int bytes, int blockSize) {
        // prevent null pointers
        if (blockSize <= 1) {
            return bytes;
        }
        return bytes - (bytes % blockSize);
    }


    /*
     * gets the number of bytes needed to play the specified number of milliseconds
     */
    static long millis2bytes(AudioFormat format, long millis) {
        long result = (long) (millis * format.getFrameRate() / 1000.0f * format.getFrameSize());
        return align(result, format.getFrameSize());
    }

    /*
     * gets the time in milliseconds for the given number of bytes
     */
    static long bytes2millis(AudioFormat format, long bytes) {
        return (long) (bytes / format.getFrameRate() * 1000.0f / format.getFrameSize());
    }

    /*
     * gets the number of bytes needed to play the specified number of microseconds
     */
    static long micros2bytes(AudioFormat format, long micros) {
        long result = (long) (micros * format.getFrameRate() / 1000000.0f * format.getFrameSize());
        return align(result, format.getFrameSize());
    }

    /*
     * gets the time in microseconds for the given number of bytes
     */
    static long bytes2micros(AudioFormat format, long bytes) {
        return (long) (bytes / format.getFrameRate() * 1000000.0f / format.getFrameSize());
    }

    /*
     * gets the number of frames needed to play the specified number of microseconds
     */
    static long micros2frames(AudioFormat format, long micros) {
        return (long) (micros * format.getFrameRate() / 1000000.0f);
    }

    /*
     * gets the time in microseconds for the given number of frames
     */
    static long frames2micros(AudioFormat format, long frames) {
        return (long) (((double) frames) / format.getFrameRate() * 1000000.0d);
    }

    static void isFullySpecifiedAudioFormat(AudioFormat format) {
        if (!format.getEncoding().equals(AudioFormat.Encoding.PCM_SIGNED)
            && !format.getEncoding().equals(AudioFormat.Encoding.PCM_UNSIGNED)
            && !format.getEncoding().equals(AudioFormat.Encoding.ULAW)
            && !format.getEncoding().equals(AudioFormat.Encoding.ALAW)) {
            // we don't know how to verify possibly non-linear encodings
            return;
        }
        if (format.getFrameRate() <= 0) {
            throw new IllegalArgumentException("invalid frame rate: "
                                               +((format.getFrameRate()==-1)?
                                                 "NOT_SPECIFIED":String.valueOf(format.getFrameRate())));
        }
        if (format.getSampleRate() <= 0) {
            throw new IllegalArgumentException("invalid sample rate: "
                                               +((format.getSampleRate()==-1)?
                                                 "NOT_SPECIFIED":String.valueOf(format.getSampleRate())));
        }
        if (format.getSampleSizeInBits() <= 0) {
            throw new IllegalArgumentException("invalid sample size in bits: "
                                               +((format.getSampleSizeInBits()==-1)?
                                                 "NOT_SPECIFIED":String.valueOf(format.getSampleSizeInBits())));
        }
        if (format.getFrameSize() <= 0) {
            throw new IllegalArgumentException("invalid frame size: "
                                               +((format.getFrameSize()==-1)?
                                                 "NOT_SPECIFIED":String.valueOf(format.getFrameSize())));
        }
        if (format.getChannels() <= 0) {
            throw new IllegalArgumentException("invalid number of channels: "
                                               +((format.getChannels()==-1)?
                                                 "NOT_SPECIFIED":String.valueOf(format.getChannels())));
        }
    }


    static boolean isFullySpecifiedPCMFormat(AudioFormat format) {
        if (!format.getEncoding().equals(AudioFormat.Encoding.PCM_SIGNED)
            && !format.getEncoding().equals(AudioFormat.Encoding.PCM_UNSIGNED)) {
            return false;
        }
        if ((format.getFrameRate() <= 0)
            || (format.getSampleRate() <= 0)
            || (format.getSampleSizeInBits() <= 0)
            || (format.getFrameSize() <= 0)
            || (format.getChannels() <= 0)) {
            return false;
        }
        return true;
    }


    public static AudioInputStream getPCMConvertedAudioInputStream(AudioInputStream ais) {
        // we can't open the device for non-PCM playback, so we have
        // convert any other encodings to PCM here (at least we try!)
        AudioFormat af = ais.getFormat();


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