/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.pdfbox.io; import java.io.InputStream; import java.io.IOException; /** * This class allows a section of a RandomAccessFile to be accessed as an * input stream. * * @author <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a> * @version $Revision: 1.5 $ */ public class RandomAccessFileInputStream extends InputStream { private RandomAccess file; private long currentPosition; private long endPosition; /** * Constructor. * * @param raFile The file to read the data from. * @param startPosition The position in the file that this stream starts. * @param length The length of the input stream. */ public RandomAccessFileInputStream( RandomAccess raFile, long startPosition, long length ) { file = raFile; currentPosition = startPosition; endPosition = currentPosition+length; } /** * {@inheritDoc} */ public int available() { return (int)(endPosition - currentPosition); } /** * {@inheritDoc} */ public void close() { //do nothing because we want to leave the random access file open. } /** * {@inheritDoc} */ public int read() throws IOException { synchronized(file) { int retval = -1; if( currentPosition < endPosition ) { file.seek( currentPosition ); currentPosition++; retval = file.read(); } return retval; } } /** * {@inheritDoc} */ public int read( byte[] b, int offset, int length ) throws IOException { //only allow a read of the amount available. if( length > available() ) { length = available(); } int amountRead = -1; //only read if there are bytes actually available, otherwise //return -1 if the EOF has been reached. if( available() > 0 ) { synchronized(file) { file.seek( currentPosition ); amountRead = file.read( b, offset, length ); } } //update the current cursor position. if( amountRead > 0 ) { currentPosition += amountRead; } return amountRead; } /** * {@inheritDoc} */ public long skip( long amountToSkip ) { long amountSkipped = Math.min( amountToSkip, available() ); currentPosition+= amountSkipped; return amountSkipped; } }