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Jlayer version used in libgdx. Fixed some NPEs, changed how buffering happens, deleted most of the classes, everything not related to decoding and half of what was related to decoding but not needed. Added support for reading replay gain out of the mp3.

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/*
 * 11/19/04 1.0 moved to LGPL. 12/12/99 Added appendSamples() method for efficiency. MDM. 15/02/99 ,Java Conversion by E.B
 * ,[email protected], JavaLayer
 * 
 * Declarations for output buffer, includes operating system implementation of the virtual Obuffer. Optional routines enabling
 * seeks and stops added by Jeff Tsay.
 * 
 * @(#) obuffer.h 1.8, last edit: 6/15/94 16:51:56
 * 
 * @(#) Copyright (C) 1993, 1994 Tobias Bading ([email protected])
 * 
 * @(#) Berlin University of Technology
 * 
 * Idea and first implementation for u-law output with fast downsampling by Jim Boucher ([email protected])
 * 
 * LinuxObuffer class written by Louis P. Kruger ([email protected])
 * ----------------------------------------------------------------------- This program is free software; you can redistribute it
 * and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 * 
 * This program 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 Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * ----------------------------------------------------------------------
 */

package javazoom.jl.decoder;

/**
 * Base Class for audio output.
 */
public class OutputBuffer {
	public static final int BUFFERSIZE = 2 * 1152; // max. 2 * 1152 samples per frame
	private static final int MAXCHANNELS = 2; // max. number of channels

	private Float replayGainScale;
	private int channels;
	private byte[] buffer;
	private int[] channelPointer;
	private boolean isBigEndian;

	public OutputBuffer (int channels, boolean isBigEndian) {
		this.channels = channels;
		this.isBigEndian = isBigEndian;
		buffer = new byte[BUFFERSIZE * channels];
		channelPointer = new int[channels];
		reset();
	}

	/**
	 * Takes a 16 Bit PCM sample.
	 */
	private void append (int channel, short value) {
		byte firstByte;
		byte secondByte;
		if (isBigEndian) {
			firstByte = (byte)(value >>> 8 & 0xFF);
			secondByte = (byte)(value & 0xFF);
		} else {
			firstByte = (byte)(value & 0xFF);
			secondByte = (byte)(value >>> 8 & 0xFF);
		}
		buffer[channelPointer[channel]] = firstByte;
		buffer[channelPointer[channel] + 1] = secondByte;
		channelPointer[channel] += channels * 2;
	}

	/**
	 * Takes 32 PCM samples.
	 */
	public void appendSamples (int channel, float[] f) {
		short s;
		if (replayGainScale != null) {
			for (int i = 0; i < 32;) {
				s = clip(f[i++] * replayGainScale);
				append(channel, s);
			}
		} else {
			for (int i = 0; i < 32;) {
				s = clip(f[i++]);
				append(channel, s);
			}
		}
	}

	public byte[] getBuffer () {
		return buffer;
	}

	public int reset () {
		try {
			int index = channels - 1;
			return channelPointer[index] - index * 2;
		} finally {
			// Points to byte location, implicitely assuming 16 bit samples.
			for (int i = 0; i < channels; i++)
				channelPointer[i] = i * 2;
		}
	}

	public void setReplayGainScale (Float replayGainScale) {
		this.replayGainScale = replayGainScale;
	}

	public boolean isStereo () {
		return channelPointer[1] == 2;
	}

	// Clip to 16 bits.
	private final short clip (float sample) {
		return sample > 32767.0f ? 32767 : sample < -32768.0f ? -32768 : (short)sample;
	}

}