190 lines
6.4 KiB
Java
190 lines
6.4 KiB
Java
/*
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* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.security;
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import java.io.IOException;
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import java.io.EOFException;
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import java.io.InputStream;
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import java.io.FilterInputStream;
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import java.io.PrintStream;
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import java.io.ByteArrayInputStream;
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/**
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* A transparent stream that updates the associated message digest using
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* the bits going through the stream.
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*
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* <p>To complete the message digest computation, call one of the
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* {@code digest} methods on the associated message
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* digest after your calls to one of this digest input stream's
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* {@link #read() read} methods.
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*
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* <p>It is possible to turn this stream on or off (see
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* {@link #on(boolean) on}). When it is on, a call to one of the
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* {@code read} methods
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* results in an update on the message digest. But when it is off,
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* the message digest is not updated. The default is for the stream
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* to be on.
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*
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* <p>Note that digest objects can compute only one digest (see
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* {@link MessageDigest}),
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* so that in order to compute intermediate digests, a caller should
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* retain a handle onto the digest object, and clone it for each
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* digest to be computed, leaving the original digest untouched.
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*
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* @see MessageDigest
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*
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* @see DigestOutputStream
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*
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* @author Benjamin Renaud
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* @since 1.2
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*/
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public class DigestInputStream extends FilterInputStream {
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/* NOTE: This should be made a generic UpdaterInputStream */
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/* Are we on or off? */
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private boolean on = true;
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/**
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* The message digest associated with this stream.
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*/
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protected MessageDigest digest;
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/**
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* Creates a digest input stream, using the specified input stream
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* and message digest.
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*
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* @param stream the input stream.
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*
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* @param digest the message digest to associate with this stream.
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*/
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public DigestInputStream(InputStream stream, MessageDigest digest) {
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super(stream);
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setMessageDigest(digest);
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}
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/**
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* Returns the message digest associated with this stream.
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*
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* @return the message digest associated with this stream.
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* @see #setMessageDigest(java.security.MessageDigest)
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*/
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public MessageDigest getMessageDigest() {
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return digest;
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}
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/**
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* Associates the specified message digest with this stream.
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*
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* @param digest the message digest to be associated with this stream.
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* @see #getMessageDigest()
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*/
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public void setMessageDigest(MessageDigest digest) {
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this.digest = digest;
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}
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/**
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* Reads a byte, and updates the message digest (if the digest
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* function is on). That is, this method reads a byte from the
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* input stream, blocking until the byte is actually read. If the
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* digest function is on (see {@link #on(boolean) on}), this method
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* will then call {@code update} on the message digest associated
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* with this stream, passing it the byte read.
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*
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* @return the byte read.
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*
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* @exception IOException if an I/O error occurs.
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*
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* @see MessageDigest#update(byte)
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*/
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public int read() throws IOException {
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int ch = in.read();
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if (on && ch != -1) {
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digest.update((byte)ch);
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}
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return ch;
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}
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/**
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* Reads into a byte array, and updates the message digest (if the
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* digest function is on). That is, this method reads up to
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* {@code len} bytes from the input stream into the array
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* {@code b}, starting at offset {@code off}. This method
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* blocks until the data is actually
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* read. If the digest function is on (see
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* {@link #on(boolean) on}), this method will then call {@code update}
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* on the message digest associated with this stream, passing it
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* the data.
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*
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* @param b the array into which the data is read.
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*
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* @param off the starting offset into {@code b} of where the
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* data should be placed.
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*
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* @param len the maximum number of bytes to be read from the input
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* stream into b, starting at offset {@code off}.
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*
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* @return the actual number of bytes read. This is less than
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* {@code len} if the end of the stream is reached prior to
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* reading {@code len} bytes. -1 is returned if no bytes were
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* read because the end of the stream had already been reached when
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* the call was made.
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*
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* @exception IOException if an I/O error occurs.
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*
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* @see MessageDigest#update(byte[], int, int)
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*/
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public int read(byte[] b, int off, int len) throws IOException {
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int result = in.read(b, off, len);
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if (on && result != -1) {
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digest.update(b, off, result);
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}
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return result;
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}
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/**
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* Turns the digest function on or off. The default is on. When
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* it is on, a call to one of the {@code read} methods results in an
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* update on the message digest. But when it is off, the message
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* digest is not updated.
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*
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* @param on true to turn the digest function on, false to turn
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* it off.
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*/
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public void on(boolean on) {
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this.on = on;
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}
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/**
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* Prints a string representation of this digest input stream and
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* its associated message digest object.
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*/
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public String toString() {
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return "[Digest Input Stream] " + digest.toString();
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}
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}
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