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Java B+Tree Key-Value Store Library
/**
* Copyright © 2005-2012 Akiban Technologies, Inc. All rights reserved.
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Public License v1.0 which
* accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* This program may also be available under different license terms.
* For more information, see www.akiban.com or contact [email protected].
*
* Contributors:
* Akiban Technologies, Inc.
*/
package com.persistit;
import java.io.Serializable;
/**
* Contains an immutable copy of the state from a {@link Value} object suitable
* for use as the key of a Map.
*
* @version 1.0
*/
public class ValueState implements Serializable {
public static final long serialVersionUID = -3715600225940676772L;
private final byte[] _bytes;
private final boolean _longRecordMode;
private int _hashCode = -1;
/**
* Construct an immutable ValueState by copying the relevant
* state information from a Value. The hashCode
* and equals methods of Value and
* ValueState are compatible so that either a
* Value or a ValueState may be used as a map key.
*
* @param value
* The Value from which the state is copied.
*/
public ValueState(final Value value) {
_longRecordMode = value.isLongRecordMode();
final int length = value.getEncodedSize();
_bytes = new byte[length];
System.arraycopy(value.getEncodedBytes(), 0, _bytes, 0, length);
}
/**
* Construct an immutable ValueState by copying the relevant
* state information from a Value. The hashCode
* and equals methods of Value and
* ValueState are compatible so that either a
* Value or a ValueState may be used as a map key.
* If the encoded size of the original value is larger than
* truncateSize, the result is truncated the that size.
*
* @param value
* The Value from which the state is copied.
*
* @param truncateSize
* Size at which the the copied encoded byte array is truncated.
*/
public ValueState(final Value value, final int truncateSize) {
_longRecordMode = value.isLongRecordMode();
int length = value.getEncodedSize();
if (length > truncateSize)
length = truncateSize;
_bytes = new byte[length];
System.arraycopy(value.getEncodedBytes(), 0, _bytes, 0, length);
}
/**
* Copies the content of this ValueState to the supplied
* Value.
*
* @param value
* The Value to which content should be copied.
*/
public void copyTo(final Value value) {
if (value.getMaximumSize() < _bytes.length) {
throw new IllegalArgumentException("Too small");
}
value.clear();
value.ensureFit(_bytes.length);
System.arraycopy(_bytes, 0, value.getEncodedBytes(), 0, _bytes.length);
value.setEncodedSize(_bytes.length);
value.setLongRecordMode(_longRecordMode);
}
/**
* The hash code for this ValueState. The hashCode is the same
* as for the equivalent Value, that is the Value
* from which this ValueState was constructed prior to any
* subsequent modifications.
*
* @return The hashCode.
*/
@Override
public int hashCode() {
if (_hashCode < 0) {
int hashCode = 0;
for (int index = 0; index < _bytes.length; index++) {
hashCode = (hashCode * 17) ^ (_bytes[index] & 0xFF);
}
_hashCode = hashCode & 0x7FFFFFFF;
}
return _hashCode;
}
/**
* Implements equals in such a way that Value and
* ValueState can be used interchangeably as map keys.
*
* @return true if the specified object is either a
* Value or a ValueState whose state
* represents an identical object or primitive value.
*/
@Override
public boolean equals(final Object obj) {
if (obj instanceof Value) {
final Value value = (Value) obj;
if (value.getEncodedSize() != _bytes.length)
return false;
final byte[] valueBytes = value.getEncodedBytes();
for (int i = 0; i < _bytes.length; i++) {
if (valueBytes[i] != _bytes[i])
return false;
}
return true;
} else if (obj instanceof ValueState) {
final ValueState valueState = (ValueState) obj;
if (valueState._bytes.length != _bytes.length)
return false;
for (int i = 0; i < _bytes.length; i++) {
if (valueState._bytes[i] != _bytes[i])
return false;
}
return true;
}
return false;
}
/**
* @return the encoded byte array. See
* {@link com.persistit.Value#getEncodedBytes()}.
*/
public byte[] getEncodedBytes() {
return _bytes;
}
/**
* @return the size of the encoded byte array. See
* {@link com.persistit.Value#getEncodedSize()}.
*/
public int getEncodedSize() {
return _bytes.length;
}
boolean isLongRecordMode() {
return _longRecordMode;
}
}