org.apache.openjpa.util.ArrayStateImage Maven / Gradle / Ivy
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* 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 org.apache.openjpa.util;
import java.util.BitSet;
import java.util.Objects;
/**
* Utilities for dealing with a simple state image consisting of an
* Object[] of field values with one extra index containing a
* {@link BitSet} of loaded fields. This simplistic state image might be used
* for optimistic versioning.
*
* @author Abe White
*/
public class ArrayStateImage {
/**
* Create a new state image for the given number of fields.
*/
public static Object[] newImage(int numFields) {
Object[] state = new Object[numFields + 1];
state[numFields] = new BitSet(numFields);
return state;
}
/**
* Return true if the given version object appears to be an array state
* image.
*/
public static boolean isImage(Object obj) {
if (!(obj instanceof Object[]))
return false;
Object[] arr = (Object[]) obj;
return arr.length > 0 && arr[arr.length - 1] instanceof BitSet;
}
/**
* Get the loaded mask from a state image.
*/
public static BitSet getLoaded(Object[] state) {
return (BitSet) state[state.length - 1];
}
/**
* Set the loaded mask into a state image.
*/
public static void setLoaded(Object[] state, BitSet loaded) {
state[state.length - 1] = loaded;
}
/**
* Clone a state array.
*/
public static Object[] clone(Object[] state) {
Object[] copy = new Object[state.length];
System.arraycopy(state, 0, copy, 0, state.length - 1);
BitSet loaded = (BitSet) state[state.length - 1];
copy[copy.length - 1] = loaded.clone();
return copy;
}
/**
* Return whether the given images are equivalent from an optimistic
* locking perspective.
*/
public static boolean sameVersion(Object[] state1, Object[] state2) {
if (state1 == state2)
return true;
// if either state is null, then we report that it is the
// same: this is because a null version will indicate that
// there are no loaded fields in the version at all, which
// indicates that there is nothing to compare
if (state1 == null || state2 == null)
return true;
// check only the fields that are in the loaded set for the
// first version
BitSet loaded1 = getLoaded(state1);
BitSet loaded2 = getLoaded(state2);
for (int i = 0, max = loaded1.length(); i < max; i++) {
if (loaded1.get(i) && loaded2.get(i)
&& !Objects.equals(state1[i], state2[i]))
return false;
}
return true;
}
}