| /* Copyright 2004 The Apache Software Foundation |
| * |
| * Licensed 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.xmlbeans; |
| |
| import javax.xml.namespace.QName; |
| |
| /** |
| * A cache that can be used to pool QName instances. Each thread has one. |
| */ |
| public final class QNameCache |
| { |
| private static final float DEFAULT_LOAD = 0.70f; |
| private final float loadFactor; |
| private int numEntries = 0; |
| private int threshold; |
| private int hashmask; |
| private QName[] table; |
| |
| /** |
| * Creates a QNameCache with the given initialCapacity and loadFactor. |
| * |
| * @param initialCapacity the number of entries to initially make space for |
| * @param loadFactor a number to control the density of the hashtable |
| */ |
| public QNameCache(int initialCapacity, float loadFactor) |
| { |
| assert initialCapacity > 0; |
| assert loadFactor > 0 && loadFactor < 1; |
| |
| // Find a power of 2 >= initialCapacity |
| int capacity = 16; |
| while (capacity < initialCapacity) |
| capacity <<= 1; |
| |
| this.loadFactor = loadFactor; |
| this.hashmask = capacity - 1; |
| threshold = (int)(capacity * loadFactor); |
| table = new QName[capacity]; |
| } |
| |
| /** |
| * Creates a QNameCache with the given initialCapacity. |
| * |
| * @param initialCapacity the number of entries to initially make space for |
| */ |
| public QNameCache(int initialCapacity) |
| { |
| this(initialCapacity, DEFAULT_LOAD); |
| } |
| |
| public QName getName(String uri, String localName) |
| { |
| return getName( uri, localName, "" ); |
| } |
| |
| /** |
| * Fetches a QName with the given namespace and localname. |
| * Creates one if one is not found in the cache. |
| * |
| * @param uri the namespace |
| * @param localName the localname |
| * @param prefix the prefix |
| * @return the cached QName |
| */ |
| public QName getName(String uri, String localName, String prefix) |
| { |
| /* |
| return new QName(uri, localName, prefix); |
| */ |
| assert localName != null; |
| |
| if (uri == null) uri = ""; |
| if (prefix == null) prefix = ""; |
| |
| int index = hash(uri, localName, prefix) & hashmask; |
| while (true) { |
| QName q = table[index]; |
| if (q == null) |
| { |
| numEntries++; |
| if (numEntries >= threshold) |
| rehash(); |
| |
| return table[index] = new QName(uri, localName, prefix); |
| } |
| else if (equals(q, uri, localName, prefix)) |
| return q; |
| else |
| index = (index-1) & hashmask; |
| } |
| } |
| |
| private void rehash() |
| { |
| int newLength = table.length * 2; |
| QName[] newTable = new QName[newLength]; |
| int newHashmask = newLength - 1; |
| |
| for (int i = 0 ; i < table.length ; i++) |
| { |
| QName q = table[i]; |
| if (q != null) |
| { |
| int newIndex = |
| hash( q.getNamespaceURI(), q.getLocalPart(), q.getPrefix() ) & newHashmask; |
| |
| while (newTable[newIndex] != null) |
| newIndex = (newIndex - 1) & newHashmask; |
| |
| newTable[newIndex] = q; |
| } |
| } |
| |
| table = newTable; |
| hashmask = newHashmask; |
| threshold = (int) (newLength * loadFactor); |
| } |
| |
| private static int hash(String uri, String localName, String prefix) |
| { |
| int h = 0; |
| |
| h += prefix.hashCode() << 10; |
| h += uri.hashCode() << 5; |
| h += localName.hashCode(); |
| |
| return h; |
| } |
| |
| private static boolean equals(QName q, String uri, String localName, String prefix) |
| { |
| return |
| q.getLocalPart().equals(localName) && |
| q.getNamespaceURI().equals(uri) && |
| q.getPrefix().equals(prefix); |
| } |
| } |