ChecksumCalculatingInputStream.java
/*
* 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.commons.compress.utils;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Objects;
import java.util.zip.Checksum;
/**
* Calculates the checksum of the data read.
*
* @NotThreadSafe
* @since 1.14
*/
public class ChecksumCalculatingInputStream extends FilterInputStream {
private final Checksum checksum;
public ChecksumCalculatingInputStream(final Checksum checksum, final InputStream inputStream) {
super(Objects.requireNonNull(inputStream, "inputStream"));
this.checksum = Objects.requireNonNull(checksum, "checksum");
}
/**
* Returns the calculated checksum.
*
* @return the calculated checksum.
*/
public long getValue() {
return checksum.getValue();
}
/**
* Reads a single byte from the stream
*
* @throws IOException if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
*/
@Override
public int read() throws IOException {
final int ret = in.read();
if (ret >= 0) {
checksum.update(ret);
}
return ret;
}
/**
* Reads from the stream into a byte array.
*
* @throws IOException if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
*/
@Override
public int read(final byte[] b, final int off, final int len) throws IOException {
if (len == 0) {
return 0;
}
final int ret = in.read(b, off, len);
if (ret >= 0) {
checksum.update(b, off, ret);
}
return ret;
}
@Override
public long skip(final long n) throws IOException {
// Can't really skip, we have to hash everything to verify the checksum
if (read() >= 0) {
return 1;
}
return 0;
}
}