| /* |
| |
| Derby - Class org.apache.derby.iapi.store.raw.ContainerLock |
| |
| 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.derby.iapi.store.raw; |
| |
| /** |
| A ContainerLock represents a qualifier that is to be used when |
| locking a container through a ContainerHandle. |
| |
| <BR> |
| MT - Immutable |
| |
| @see ContainerHandle |
| @see LockingPolicy |
| */ |
| |
| public final class ContainerLock { |
| |
| /** Integer representation of the type of the lock. */ |
| private final int type; |
| /** Bit mask with one bit set. The position of the bit tells the type of |
| * the lock. */ |
| private final int typeBit; |
| /** Bit mask which represents the lock types that are compatible with this |
| * lock type. */ |
| private final int compat; |
| |
| /** Number of types of container locks. */ |
| public static final int C_NUMBER = 5; |
| |
| /** Container lock compatibility table. */ |
| private static final boolean[][] C_COMPAT = { |
| |
| // Granted |
| // Request \ CIS CIX CS CU CX |
| // |
| /* CIS */ { true, true, true, false, false }, |
| /* CIX */ { true, true, false, false, false }, |
| /* CS */ { true, false, true, false, false }, |
| /* CU */ { false, false, true, false, false }, |
| /* CX */ { false, false, false, false, false } |
| |
| }; |
| |
| private ContainerLock(int type) { |
| this.type = type; |
| typeBit = (1 << type); |
| int bitmask = 0; |
| for (int i = 0; i < C_NUMBER; i++) { |
| // set a bit in bitmask for each compatible lock type |
| if (C_COMPAT[type][i]) { |
| bitmask |= (1 << i); |
| } |
| } |
| compat = bitmask; |
| } |
| |
| // Names of locks for virtual lock table print out |
| private static String[] shortnames = {"IS", "IX", "S", "U", "X" }; |
| |
| /** Container Intent Shared lock */ |
| public static final ContainerLock CIS = new ContainerLock(0); |
| /** Container Intent Exclusive lock */ |
| public static final ContainerLock CIX = new ContainerLock(1); |
| /** Container Shared lock */ |
| public static final ContainerLock CS = new ContainerLock(2); |
| /** Container Update lock */ |
| public static final ContainerLock CU = new ContainerLock(3); |
| /** Container Exclusive lock */ |
| public static final ContainerLock CX = new ContainerLock(4); |
| |
| /** |
| Get an integer representation of the type of the lock. This method is guaranteed |
| to return an integer >= 0 and &t; C_NUMBER. No correlation between the value |
| and one of the static variables (CIS etc.) is guaranteed, except that |
| the values returned do not change. |
| */ |
| public int getType() { |
| return type; |
| } |
| |
| public boolean isCompatible(ContainerLock granted) { |
| return (granted.typeBit & compat) != 0; |
| } |
| |
| public String toString() { |
| |
| return shortnames[getType()]; |
| } |
| } |