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/*
* Copyright 2005 The Apache Software Foundation.
*
* Licensed 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.
*/
/* $Id$ */
package org.apache.fop.util;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* This class is a FilterInputStream descendant that reads from an underlying InputStream
* up to a defined number of bytes or the end of the underlying stream. Closing this InputStream
* will not result in the underlying InputStream to be closed, too.
* <p>
* This InputStream can be used to read chunks from a larger file of which the length is
* known in advance.
*/
public class SubInputStream extends FilterInputStream {
/** Indicates the number of bytes remaning to be read from the underlying InputStream. */
private long bytesToRead;
/**
* Creates a new SubInputStream.
* @param in the InputStream to read from
* @param maxLen the maximum number of bytes to read from the underlying InputStream until
* the end-of-file is signalled.
*/
public SubInputStream(InputStream in, long maxLen) {
super(in);
this.bytesToRead = maxLen;
}
/** @see java.io.InputStream#read() */
public int read() throws IOException {
if (bytesToRead > 0) {
int result = super.read();
if (result <= 0) {
bytesToRead--;
return result;
} else {
return -1;
}
} else {
return -1;
}
}
/** @see java.io.InputStream#read(byte[], int, int) */
public int read(byte[] b, int off, int len) throws IOException {
if (bytesToRead == 0) {
return -1;
}
int effRead = (int)Math.min(bytesToRead, len);
//cast to int is safe because len can never be bigger than Integer.MAX_VALUE
int result = super.read(b, off, effRead);
if (result >= 0) {
bytesToRead -= result;
}
return result;
}
/** @see java.io.InputStream#skip(long) */
public long skip(long n) throws IOException {
long effRead = Math.min(bytesToRead, n);
long result = super.skip(effRead);
bytesToRead -= result;
return result;
}
/** @see java.io.InputStream#close() */
public void close() throws IOException {
//Don't close the underlying InputStream!!!
this.bytesToRead = 0;
}
}
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