author | sherman |
Thu, 15 Aug 2013 10:41:59 -0700 | |
changeset 19415 | af60b1abf237 |
parent 14342 | 8435a30053c1 |
child 23010 | 6dadb192ad81 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 1996, 2011, 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.util.zip; |
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import java.nio.ByteBuffer; |
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import sun.nio.ch.DirectBuffer; |
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/** |
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* A class that can be used to compute the CRC-32 of a data stream. |
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* |
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* <p> Passing a {@code null} argument to a method in this class will cause |
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* a {@link NullPointerException} to be thrown. |
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* |
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* @see Checksum |
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* @author David Connelly |
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*/ |
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public |
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class CRC32 implements Checksum { |
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private int crc; |
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/** |
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* Creates a new CRC32 object. |
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*/ |
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public CRC32() { |
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} |
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/** |
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* Updates the CRC-32 checksum with the specified byte (the low |
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* eight bits of the argument b). |
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* |
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* @param b the byte to update the checksum with |
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*/ |
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public void update(int b) { |
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crc = update(crc, b); |
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} |
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/** |
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* Updates the CRC-32 checksum with the specified array of bytes. |
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* |
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* @throws ArrayIndexOutOfBoundsException |
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* if {@code off} is negative, or {@code len} is negative, |
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* or {@code off+len} is greater than the length of the |
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* array {@code b} |
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*/ |
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public void update(byte[] b, int off, int len) { |
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if (b == null) { |
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throw new NullPointerException(); |
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} |
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if (off < 0 || len < 0 || off > b.length - len) { |
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throw new ArrayIndexOutOfBoundsException(); |
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} |
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crc = updateBytes(crc, b, off, len); |
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} |
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/** |
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* Updates the CRC-32 checksum with the specified array of bytes. |
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* |
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* @param b the array of bytes to update the checksum with |
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*/ |
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public void update(byte[] b) { |
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crc = updateBytes(crc, b, 0, b.length); |
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} |
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/** |
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* Updates the checksum with the bytes from the specified buffer. |
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* |
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* The checksum is updated using |
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* buffer.{@link java.nio.Buffer#remaining() remaining()} |
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* bytes starting at |
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* buffer.{@link java.nio.Buffer#position() position()} |
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* Upon return, the buffer's position will |
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* be updated to its limit; its limit will not have been changed. |
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* |
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* @param buffer the ByteBuffer to update the checksum with |
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* @since 1.8 |
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*/ |
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public void update(ByteBuffer buffer) { |
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int pos = buffer.position(); |
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int limit = buffer.limit(); |
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assert (pos <= limit); |
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int rem = limit - pos; |
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if (rem <= 0) |
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return; |
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if (buffer instanceof DirectBuffer) { |
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crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem); |
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} else if (buffer.hasArray()) { |
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crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem); |
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} else { |
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byte[] b = new byte[rem]; |
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buffer.get(b); |
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crc = updateBytes(crc, b, 0, b.length); |
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} |
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buffer.position(limit); |
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} |
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/** |
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* Resets CRC-32 to initial value. |
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*/ |
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public void reset() { |
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crc = 0; |
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} |
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/** |
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* Returns CRC-32 value. |
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*/ |
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public long getValue() { |
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return (long)crc & 0xffffffffL; |
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} |
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private native static int update(int crc, int b); |
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private native static int updateBytes(int crc, byte[] b, int off, int len); |
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private native static int updateByteBuffer(int adler, long addr, |
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int off, int len); |
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} |