it.unimi.dsi.io.MultipleInputStream Maven / Gradle / Ivy
Show all versions of dsi-utils Show documentation
package it.unimi.dsi.io;
/*
* DSI utilities
*
* Copyright (C) 2003-2009 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.objects.ObjectArrays;
import java.io.IOException;
import java.io.InputStream;
/** A multiple input stream.
*
* Instances of this class encapsulate a sequence of input streams.
* When one of the streams is exhausted, the multiple stream behaves as if on an end of file.
* However, after calling {@link #reset()} the stream is again readable, and positioned
* at the start of the following stream.
*/
public class MultipleInputStream extends InputStream {
/** The sequence of input streams that will be returned. */
private final InputStream[] inputStream;
/** The first output stream in {@link #inputStream} to be used. */
private final int from;
/** The last element of {@link #inputStream} to be used plus one. */
private final int to;
/** The index of the current input stream in {@link #inputStream}. */
private int curr;
/** The current input stream. */
private InputStream currStream;
/** Creates a new multiple input stream by encapsulating a nonempty fragment of an array of input streams.
*
* @param inputStream an array of input streams, that will be encapsulated.
* @param offset the first input stream that will be encapsulated.
* @param length the number of input streams to be encapsulated; it must be positive.
*/
private MultipleInputStream( final InputStream[] inputStream, final int offset, final int length ) {
ObjectArrays.ensureOffsetLength( inputStream, offset, length );
this.inputStream = inputStream;
this.from = offset;
this.to = offset + length;
curr = offset;
currStream = inputStream[ curr ];
}
/** Returns an input stream encapsulating a nonempty fragment of an array of input streams.
*
* @param inputStream an array of input streams, that will be encapsulated.
* @param offset the first input stream that will be encapsulated.
* @param length the number of input streams to be encapsulated.
* @return an input stream encapsulating the argument streams (the only argument, if length is 1).
*/
public static InputStream getStream( final InputStream[] inputStream, final int offset, final int length ) {
if ( length == 0 ) return NullInputStream.getInstance();
if ( length == 1 ) return inputStream[ offset ];
return new MultipleInputStream( inputStream, offset ,length );
}
/** Returns an input stream encapsulating a nonempty array of input streams.
*
*
Note that if inputStream.length is 1 this method will return the only stream
* that should be encapsulated.
*
* @param inputStream an array of input streams, that will be encapsulated.
* @return an input stream encapsulating the argument streams (the only argument, if the length is 1).
*/
public static InputStream getStream( final InputStream[] inputStream ) {
return getStream( inputStream, 0, inputStream.length );
}
public int available() throws IOException {
return currStream.available();
}
public void close() throws IOException {
for( int i = from; i < to; i++ ) inputStream[ i ].close();
}
public boolean markSupported() {
return false;
}
public int read() throws IOException {
return currStream.read();
}
public int read( final byte[] b, final int off, final int len ) throws IOException {
return currStream.read( b, off, len );
}
public int read( final byte[] b ) throws IOException {
return currStream.read( b );
}
public synchronized void reset() throws IOException {
if ( curr == to - 1 ) throw new IOException( "The streams in this multiple input stream have been exhausted" );
currStream = inputStream[ ++curr ];
}
public long skip( final long n ) throws IOException {
return currStream.skip( n );
}
}