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CRC32.java
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139 lines (126 loc) · 3.39 KB
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/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.util.zip;
import java.nio.ByteBuffer;
import sun.nio.ch.DirectBuffer;
/**
* A class that can be used to compute the CRC-32 of a data stream.
*
* <p> Passing a {@code null} argument to a method in this class will cause
* a {@link NullPointerException} to be thrown.
*
* @see Checksum
* @author David Connelly
*/
public
class CRC32 implements Checksum {
private int crc;
/**
* Creates a new CRC32 object.
*/
public CRC32() {
}
/**
* Updates the CRC-32 checksum with the specified byte (the low
* eight bits of the argument b).
*
* @param b the byte to update the checksum with
*/
public void update(int b) {
crc = update(crc, b);
}
/**
* Updates the CRC-32 checksum with the specified array of bytes.
*
* @throws ArrayIndexOutOfBoundsException
* if {@code off} is negative, or {@code len} is negative,
* or {@code off+len} is greater than the length of the
* array {@code b}
*/
public void update(byte[] b, int off, int len) {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
crc = updateBytes(crc, b, off, len);
}
/**
* Updates the CRC-32 checksum with the specified array of bytes.
*
* @param b the array of bytes to update the checksum with
*/
public void update(byte[] b) {
crc = updateBytes(crc, b, 0, b.length);
}
/**
* Updates the checksum with the bytes from the specified buffer.
*
* The checksum is updated using
* buffer.{@link java.nio.Buffer#remaining() remaining()}
* bytes starting at
* buffer.{@link java.nio.Buffer#position() position()}
* Upon return, the buffer's position will
* be updated to its limit; its limit will not have been changed.
*
* @param buffer the ByteBuffer to update the checksum with
* @since 1.8
*/
public void update(ByteBuffer buffer) {
int pos = buffer.position();
int limit = buffer.limit();
assert (pos <= limit);
int rem = limit - pos;
if (rem <= 0)
return;
if (buffer instanceof DirectBuffer) {
crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem);
} else if (buffer.hasArray()) {
crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem);
} else {
byte[] b = new byte[rem];
buffer.get(b);
crc = updateBytes(crc, b, 0, b.length);
}
buffer.position(limit);
}
/**
* Resets CRC-32 to initial value.
*/
public void reset() {
crc = 0;
}
/**
* Returns CRC-32 value.
*/
public long getValue() {
return (long)crc & 0xffffffffL;
}
private native static int update(int crc, int b);
private native static int updateBytes(int crc, byte[] b, int off, int len);
private native static int updateByteBuffer(int adler, long addr,
int off, int len);
}