/*
* 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 java.util.zip;
import java.io.IOException;
import java.io.OutputStream;
/**
* The {@code CheckedOutputStream} class is used to maintain a running checksum
* of all data written to a stream. The purpose of this checksum is to establish
* data integrity, by publishing the checksum to other parties wanting to read
* the non corrupted data.
*/
public class CheckedOutputStream extends java.io.FilterOutputStream {
private final Checksum check;
/**
* Constructs a new {@code CheckedOutputStream} on {@code OutputStream}
* {@code os}. The checksum is calculated using the algorithm implemented
* by {@code csum}.
*
* @param os
* the output stream to calculate checksum for.
* @param cs
* an entity implementing the checksum algorithm.
*/
public CheckedOutputStream(OutputStream os, Checksum cs) {
super(os);
check = cs;
}
/**
* Returns the checksum calculated on the stream read so far.
*
* @return the updated checksum.
*/
public Checksum getChecksum() {
return check;
}
/**
* Writes the specified byte to the underlying stream. The checksum is
* updated with {@code val}.
*
* @param val
* the data value to written to the output stream.
* @throws IOException
* if an IO error has occurred.
*/
@Override
public void write(int val) throws IOException {
out.write(val);
check.update(val);
}
/**
* Writes n bytes of data from {@code buf} starting at offset {@code off} to
* the underlying stream. The checksum is updated with the bytes written.
*
* @param buf
* data written to the output stream.
* @param off
* the offset to start reading the data from {@code buf} written
* to the output stream.
* @param nbytes
* number of bytes to write to the output stream.
* @throws IOException
* if an IO error has occurred.
*/
@Override
public void write(byte[] buf, int off, int nbytes) throws IOException {
out.write(buf, off, nbytes);
check.update(buf, off, nbytes);
}
}