java.security.DigestInputStream Maven / Gradle / Ivy
/*
* 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.security;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* {@code DigestInputStream} is a {@code FilterInputStream} which maintains an
* associated message digest.
*/
public class DigestInputStream extends FilterInputStream {
/**
* The message digest for this stream.
*/
protected MessageDigest digest;
// Indicates whether digest functionality is on or off
private boolean isOn = true;
/**
* Constructs a new instance of this {@code DigestInputStream}, using the
* given {@code stream} and the {@code digest}.
*
* Warning: passing a null source creates an invalid
* {@code DigestInputStream}. All operations on such a stream will fail.
*
* @param stream
* the input stream.
* @param digest
* the message digest.
*/
public DigestInputStream(InputStream stream, MessageDigest digest) {
super(stream);
this.digest = digest;
}
/**
* Returns the message digest for this stream.
*
* @return the message digest for this stream.
*/
public MessageDigest getMessageDigest() {
return digest;
}
/**
* Sets the message digest which this stream will use.
*
* @param digest
* the message digest which this stream will use.
*/
public void setMessageDigest(MessageDigest digest) {
this.digest = digest;
}
/**
* Reads the next byte and returns it as an {@code int}. Updates the digest
* for the byte if this function is {@link #on(boolean)}.
*
* This operation is blocking.
*
* @return the byte which was read or -1 at end of stream.
* @throws IOException
* if reading the source stream causes an {@code IOException}.
*/
@Override
public int read() throws IOException {
// read the next byte
int byteRead = in.read();
// update digest only if
// - digest functionality is on
// - eos has not been reached
if (isOn && (byteRead != -1)) {
digest.update((byte)byteRead);
}
// return byte read
return byteRead;
}
/**
* Reads up to {@code byteCount} bytes into {@code buffer}, starting at
* {@code byteOffset}. Updates the digest if this function is
* {@link #on(boolean)}.
*
*
This operation is blocking.
*
*
Returns the number of bytes actually read or -1 if the end of the
* filtered stream has been reached while reading.
*
* @throws IOException
* if reading the source stream causes an {@code IOException}
*/
@Override
public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
int bytesRead = in.read(buffer, byteOffset, byteCount);
// update digest only if
// - digest functionality is on
// - eos has not been reached
if (isOn && (bytesRead != -1)) {
digest.update(buffer, byteOffset, bytesRead);
}
// return number of bytes read
return bytesRead;
}
/**
* Enables or disables the digest function (default is on).
*
* @param on
* {@code true} if the digest should be computed, {@code false}
* otherwise.
* @see MessageDigest
*/
public void on(boolean on) {
isOn = on;
}
/**
* Returns a string containing a concise, human-readable description of this
* {@code DigestInputStream} including the digest.
*
* @return a printable representation for this {@code DigestInputStream}.
*/
@Override
public String toString() {
return super.toString() + ", " + digest.toString() +
(isOn ? ", is on" : ", is off");
}
}