bytebufferinputstream.java

来自「MG4J (Managing Gigabytes for Java) is a 」· Java 代码 · 共 116 行

package it.unimi.dsi.mg4j.io;

/*		 
 * MG4J: Managing Gigabytes for Java
 *
 * Copyright (C) 2007 Sebastiano Vigna 
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 2.1 of the License, or (at your option)
 *  any later version.
 *
 *  This library 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 Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */

import it.unimi.dsi.fastutil.io.MeasurableInputStream;
import it.unimi.dsi.fastutil.io.RepositionableStream;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;


/** A bridge between byte {@linkplain ByteBuffer buffers} and {@linkplain InputStream input streams}.
 * 
 * <p>The main usefulness of this class is that of making it possible creating input streams
 * that are really based on a {@link MappedByteBuffer}.
 * 
 * @author Sebastiano Vigna
 * @since 1.2
 * @deprecated Moved to <code>dsiutils</code>.
 */

@Deprecated
public class ByteBufferInputStream extends MeasurableInputStream implements RepositionableStream {

	/** The underlying byte buffer. */
	private final ByteBuffer byteBuffer;

	/** The current mark as a position, or -1 if no mark exists. */
	private int mark = -1;

	/** Creates a new byte-buffer input stream.
	 * 
	 * @param byteBuffer the underlying byte buffer.
	 */
	
	public ByteBufferInputStream( final ByteBuffer byteBuffer ) {
		this.byteBuffer = byteBuffer;
	}

	public int available() {
		return byteBuffer.remaining();
	}

	@Override
	public boolean markSupported() {
		return true;
	}

	@Override
	public synchronized void mark( final int unused ) {
		this.mark = byteBuffer.position();
	}

	@Override
	public synchronized void reset() throws IOException {
		if ( mark == -1 ) throw new IOException();
		position( mark );
	}

	@Override
	public long skip( final long n ) throws IOException {
		final int toSkip = (int)Math.min( byteBuffer.remaining(), n );
		position( position() + toSkip );
		return toSkip;
	}

	@Override
	public int read() {
		if ( ! byteBuffer.hasRemaining() ) return -1;
		return byteBuffer.get() & 0xFF;
	}

	public int read( final byte[] b, final int offset, final int length ) {
		if ( length == 0 ) return 0;
		if ( ! byteBuffer.hasRemaining() ) return -1;
		final int realLength = Math.min( byteBuffer.remaining(), length );
		byteBuffer.get( b, offset, realLength );
		return realLength;
	}

	@Override
	public long length() throws IOException {
		return byteBuffer.capacity();
	}

	@Override
	public long position() throws IOException {
		return byteBuffer.position();
	}
	
	public void position( final long newPosition ) throws IOException {
		byteBuffer.position( (int)Math.min( newPosition, length() ) );
	}
	
}