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// Copyright 2016 Google Inc. All rights reserved.
//
// 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.
package com.google.archivepatcher.applier;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* A stream that simulates EOF after a specified numToRead of bytes has been reached.
*/
public class LimitedInputStream extends FilterInputStream {
/**
* Current numToRead.
*/
private long numToRead;
/**
* Buffer used for one-byte reads to keep all code on the same path.
*/
private byte[] ONE_BYTE = new byte[1];
/**
* Creates a new limited stream that delegates operations to the specified stream.
* @param in the stream to limit
* @param numToRead the number of reads to allow before returning EOF
*/
public LimitedInputStream(InputStream in, long numToRead) {
super(in);
if (numToRead < 0) {
throw new IllegalArgumentException("numToRead must be >= 0: " + numToRead);
}
this.numToRead = numToRead;
}
@Override
public int read() throws IOException {
if (read(ONE_BYTE, 0, 1) == 1) {
return ONE_BYTE[0];
}
return -1;
}
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (numToRead == 0) {
return -1; // Simulate EOF
}
int maxRead = (int) Math.min(len, numToRead);
int numRead = in.read(b, off, maxRead);
if (numRead > 0) {
numToRead -= numRead;
}
return numRead;
}
}