| /* Copyright (C) 2003 Vladimir Roubtsov. All rights reserved. |
| * |
| * This program and the accompanying materials are made available under |
| * the terms of the Common Public License v1.0 which accompanies this distribution, |
| * and is available at http://www.eclipse.org/legal/cpl-v10.html |
| * |
| * $Id: IntObjectMap.java,v 1.1.1.1 2004/05/09 16:57:53 vlad_r Exp $ |
| */ |
| package com.vladium.util; |
| |
| import java.io.Serializable; |
| |
| // ---------------------------------------------------------------------------- |
| /** |
| * |
| * MT-safety: an instance of this class is <I>not</I> safe for access from |
| * multiple concurrent threads [even if access is done by a single thread at a |
| * time]. The caller is expected to synchronize externally on an instance [the |
| * implementation does not do internal synchronization for the sake of efficiency]. |
| * java.util.ConcurrentModificationException is not supported either. |
| * |
| * @author Vlad Roubtsov, (C) 2001 |
| */ |
| public |
| final class IntObjectMap implements Serializable |
| { |
| // public: ................................................................ |
| |
| /** |
| * Equivalent to <CODE>IntObjectMap(11, 0.75F)</CODE>. |
| */ |
| public IntObjectMap () |
| { |
| this (11, 0.75F); |
| } |
| |
| /** |
| * Equivalent to <CODE>IntObjectMap(capacity, 0.75F)</CODE>. |
| */ |
| public IntObjectMap (final int initialCapacity) |
| { |
| this (initialCapacity, 0.75F); |
| } |
| |
| /** |
| * Constructs an IntObjectMap with specified initial capacity and load factor. |
| * |
| * @param initialCapacity initial number of hash buckets in the table [may not be negative, 0 is equivalent to 1]. |
| * @param loadFactor the load factor to use to determine rehashing points [must be in (0.0, 1.0] range]. |
| */ |
| public IntObjectMap (int initialCapacity, final float loadFactor) |
| { |
| if (initialCapacity < 0) throw new IllegalArgumentException ("negative input: initialCapacity [" + initialCapacity + "]"); |
| if ((loadFactor <= 0.0) || (loadFactor >= 1.0 + 1.0E-6)) |
| throw new IllegalArgumentException ("loadFactor not in (0.0, 1.0] range: " + loadFactor); |
| |
| if (initialCapacity == 0) initialCapacity = 1; |
| |
| m_loadFactor = loadFactor > 1.0 ? 1.0F : loadFactor; |
| m_sizeThreshold = (int) (initialCapacity * loadFactor); |
| m_buckets = new Entry [initialCapacity]; |
| } |
| |
| |
| /** |
| * Overrides Object.toString() for debug purposes. |
| */ |
| public String toString () |
| { |
| final StringBuffer s = new StringBuffer (); |
| debugDump (s); |
| |
| return s.toString (); |
| } |
| |
| /** |
| * Returns the number of key-value mappings in this map. |
| */ |
| public int size () |
| { |
| return m_size; |
| } |
| |
| public boolean contains (final int key) |
| { |
| // index into the corresponding hash bucket: |
| final Entry [] buckets = m_buckets; |
| final int bucketIndex = (key & 0x7FFFFFFF) % buckets.length; |
| |
| // traverse the singly-linked list of entries in the bucket: |
| for (Entry entry = buckets [bucketIndex]; entry != null; entry = entry.m_next) |
| { |
| if (key == entry.m_key) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /** |
| * Returns the value that is mapped to a given 'key'. Returns |
| * null if (a) this key has never been mapped or (b) it has been |
| * mapped to a null value. |
| * |
| * @param key mapping key |
| * |
| * @return Object value mapping for 'key' [can be null]. |
| */ |
| public Object get (final int key) |
| { |
| // index into the corresponding hash bucket: |
| final Entry [] buckets = m_buckets; |
| final int bucketIndex = (key & 0x7FFFFFFF) % buckets.length; |
| |
| // traverse the singly-linked list of entries in the bucket: |
| for (Entry entry = buckets [bucketIndex]; entry != null; entry = entry.m_next) |
| { |
| if (key == entry.m_key) |
| return entry.m_value; |
| } |
| |
| return null; |
| } |
| |
| public int [] keys () |
| { |
| if (m_size == 0) |
| return IConstants.EMPTY_INT_ARRAY; |
| else |
| { |
| final int [] result = new int [m_size]; |
| int scan = 0; |
| |
| for (int b = 0; b < m_buckets.length; ++ b) |
| { |
| for (Entry entry = m_buckets [b]; entry != null; entry = entry.m_next) |
| { |
| result [scan ++] = entry.m_key; |
| } |
| } |
| |
| return result; |
| } |
| } |
| |
| /** |
| * Updates the table to map 'key' to 'value'. Any existing mapping is overwritten. |
| * |
| * @param key mapping key |
| * @param value mapping value [can be null]. |
| * |
| * @return Object previous value mapping for 'key' [can be null] |
| */ |
| public Object put (final int key, final Object value) |
| { |
| Entry currentKeyEntry = null; |
| |
| // detect if 'key' is already in the table [in which case, set 'currentKeyEntry' to point to its entry]: |
| |
| // index into the corresponding hash bucket: |
| int bucketIndex = (key & 0x7FFFFFFF) % m_buckets.length; |
| |
| // traverse the singly-linked list of entries in the bucket: |
| Entry [] buckets = m_buckets; |
| for (Entry entry = buckets [bucketIndex]; entry != null; entry = entry.m_next) |
| { |
| if (key == entry.m_key) |
| { |
| currentKeyEntry = entry; |
| break; |
| } |
| } |
| |
| if (currentKeyEntry != null) |
| { |
| // replace the current value: |
| |
| final Object currentKeyValue = currentKeyEntry.m_value; |
| currentKeyEntry.m_value = value; |
| |
| return currentKeyValue; |
| } |
| else |
| { |
| // add a new entry: |
| |
| if (m_size >= m_sizeThreshold) rehash (); |
| |
| buckets = m_buckets; |
| bucketIndex = (key & 0x7FFFFFFF) % buckets.length; |
| final Entry bucketListHead = buckets [bucketIndex]; |
| final Entry newEntry = new Entry (key, value, bucketListHead); |
| buckets [bucketIndex] = newEntry; |
| |
| ++ m_size; |
| |
| return null; |
| } |
| } |
| |
| // protected: ............................................................. |
| |
| // package: ............................................................... |
| |
| |
| void debugDump (final StringBuffer out) |
| { |
| if (out != null) |
| { |
| out.append (super.toString ()); out.append (EOL); |
| out.append ("size = " + m_size + ", bucket table size = " + m_buckets.length + ", load factor = " + m_loadFactor + EOL); |
| out.append ("size threshold = " + m_sizeThreshold + EOL); |
| } |
| } |
| |
| // private: ............................................................... |
| |
| |
| /** |
| * The structure used for chaining colliding keys. |
| */ |
| private static final class Entry implements Serializable |
| { |
| Entry (final int key, final Object value, final Entry next) |
| { |
| m_key = key; |
| m_value = value; |
| m_next = next; |
| } |
| |
| Object m_value; // reference to the value [never null] |
| final int m_key; |
| |
| Entry m_next; // singly-linked list link |
| |
| } // end of nested class |
| |
| |
| /** |
| * Re-hashes the table into a new array of buckets. |
| */ |
| private void rehash () |
| { |
| // TODO: it is possible to run this method twice, first time using the 2*k+1 prime sequencer for newBucketCount |
| // and then with that value reduced to actually shrink capacity. As it is right now, the bucket table can |
| // only grow in size |
| |
| final Entry [] buckets = m_buckets; |
| |
| final int newBucketCount = (m_buckets.length << 1) + 1; |
| final Entry [] newBuckets = new Entry [newBucketCount]; |
| |
| // rehash all entry chains in every bucket: |
| for (int b = 0; b < buckets.length; ++ b) |
| { |
| for (Entry entry = buckets [b]; entry != null; ) |
| { |
| final Entry next = entry.m_next; // remember next pointer because we are going to reuse this entry |
| final int entryKey = entry.m_key; |
| |
| // index into the corresponding new hash bucket: |
| final int newBucketIndex = (entryKey & 0x7FFFFFFF) % newBucketCount; |
| |
| final Entry bucketListHead = newBuckets [newBucketIndex]; |
| entry.m_next = bucketListHead; |
| newBuckets [newBucketIndex] = entry; |
| |
| entry = next; |
| } |
| } |
| |
| |
| m_sizeThreshold = (int) (newBucketCount * m_loadFactor); |
| m_buckets = newBuckets; |
| } |
| |
| |
| private final float m_loadFactor; // determines the setting of m_sizeThreshold |
| |
| private Entry [] m_buckets; // table of buckets |
| private int m_size; // number of keys in the table, not cleared as of last check |
| private int m_sizeThreshold; // size threshold for rehashing |
| |
| private static final String EOL = System.getProperty ("line.separator", "\n"); |
| |
| } // end of class |
| // ---------------------------------------------------------------------------- |
| |