aoqi@0: /*
aoqi@0:  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.  Oracle designates this
aoqi@0:  * particular file as subject to the "Classpath" exception as provided
aoqi@0:  * by Oracle in the LICENSE file that accompanied this code.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  */
aoqi@0: 
aoqi@0: package com.sun.tools.javac.util;
aoqi@0: 
aoqi@0: /**
aoqi@0:  * A hash table that maps Object to int.
aoqi@0:  *
aoqi@0:  * This is a custom hash table optimised for the Object -> int
aoqi@0:  * maps. This is done to avoid unnecessary object allocation in the image set.
aoqi@0:  *
aoqi@0:  * @author Charles Turner
aoqi@0:  * @author Per Bothner
aoqi@0:  */
aoqi@0: public class IntHashTable {
aoqi@0:     private static final int DEFAULT_INITIAL_SIZE = 64;
aoqi@0:     protected Object[] objs; // the domain set
aoqi@0:     protected int[] ints; // the image set
aoqi@0:     protected int mask; // used to clip int's into the domain
aoqi@0:     protected int num_bindings; // the number of mappings (including DELETED)
aoqi@0:     private final static Object DELETED = new Object();
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Construct an Object -> int hash table.
aoqi@0:      *
aoqi@0:      * The default size of the hash table is 64 mappings.
aoqi@0:      */
aoqi@0:     public IntHashTable() {
aoqi@0:         objs = new Object[DEFAULT_INITIAL_SIZE];
aoqi@0:         ints = new int[DEFAULT_INITIAL_SIZE];
aoqi@0:         mask = DEFAULT_INITIAL_SIZE - 1;
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Construct an Object -> int hash table with a specified amount of mappings.
aoqi@0:      * @param capacity The number of default mappings in this hash table.
aoqi@0:      */
aoqi@0:     public IntHashTable(int capacity) {
aoqi@0:         int log2Size = 4;
aoqi@0:         while (capacity > (1 << log2Size)) {
aoqi@0:             log2Size++;
aoqi@0:         }
aoqi@0:         capacity = 1 << log2Size;
aoqi@0:         objs = new Object[capacity];
aoqi@0:         ints = new int[capacity];
aoqi@0:         mask = capacity - 1;
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Compute the hash code of a given object.
aoqi@0:      *
aoqi@0:      * @param key The object whose hash code is to be computed.
aoqi@0:      * @return zero if the object is null, otherwise the identityHashCode
aoqi@0:      */
aoqi@0:     public int hash(Object key) {
aoqi@0:         return System.identityHashCode(key);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Find either the index of a key's value, or the index of an available space.
aoqi@0:      *
aoqi@0:      * @param key The key to whose value you want to find.
aoqi@0:      * @param hash The hash code of this key.
aoqi@0:      * @return Either the index of the key's value, or an index pointing to
aoqi@0:      * unoccupied space.
aoqi@0:      */
aoqi@0:     public int lookup(Object key, int hash) {
aoqi@0:         Object node;
aoqi@0:         int hash1 = hash ^ (hash >>> 15);
aoqi@0:         int hash2 = (hash ^ (hash << 6)) | 1; //ensure coprimeness
aoqi@0:         int deleted = -1;
aoqi@0:         for (int i = hash1 & mask;; i = (i + hash2) & mask) {
aoqi@0:             node = objs[i];
aoqi@0:             if (node == key)
aoqi@0:                 return i;
aoqi@0:             if (node == null)
aoqi@0:                 return deleted >= 0 ? deleted : i;
aoqi@0:             if (node == DELETED && deleted < 0)
aoqi@0:                 deleted = i;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Lookup a given key's value in the hash table.
aoqi@0:      *
aoqi@0:      * @param key The key whose value you want to find.
aoqi@0:      * @return Either the index of the key's value, or an index pointing to
aoqi@0:      * unoccupied space.
aoqi@0:      */
aoqi@0:     public int lookup(Object key) {
aoqi@0:         return lookup(key, hash(key));
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Return the value stored at the specified index in the table.
aoqi@0:      *
aoqi@0:      * @param index The index to inspect, as returned from {@link #lookup}
aoqi@0:      * @return A non-negative integer if the index contains a non-null
aoqi@0:      *         value, or -1 if it does.
aoqi@0:      */
aoqi@0:     public int getFromIndex(int index) {
aoqi@0:         Object node = objs[index];
aoqi@0:         return node == null || node == DELETED ? -1 : ints[index];
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Associates the specified key with the specified value in this map.
aoqi@0:      *
aoqi@0:      * @param key key with which the specified value is to be associated.
aoqi@0:      * @param value value to be associated with the specified key.
aoqi@0:      * @param index the index at which to place this binding, as returned
aoqi@0:      *              from {@link #lookup}.
aoqi@0:      * @return previous value associated with specified key, or -1 if there was
aoqi@0:      * no mapping for key.
aoqi@0:      */
aoqi@0:     public int putAtIndex(Object key, int value, int index) {
aoqi@0:         Object old = objs[index];
aoqi@0:         if (old == null || old == DELETED) {
aoqi@0:             objs[index] = key;
aoqi@0:             ints[index] = value;
aoqi@0:             if (old != DELETED)
aoqi@0:                 num_bindings++;
aoqi@0:             if (3 * num_bindings >= 2 * objs.length)
aoqi@0:                 rehash();
aoqi@0:             return -1;
aoqi@0:         } else { // update existing mapping
aoqi@0:             int oldValue = ints[index];
aoqi@0:             ints[index] = value;
aoqi@0:             return oldValue;
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     public int remove(Object key) {
aoqi@0:         int index = lookup(key);
aoqi@0:         Object old = objs[index];
aoqi@0:         if (old == null || old == DELETED)
aoqi@0:             return -1;
aoqi@0:         objs[index] = DELETED;
aoqi@0:         return ints[index];
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Expand the hash table when it exceeds the load factor.
aoqi@0:      *
aoqi@0:      * Rehash the existing objects.
aoqi@0:      */
aoqi@0:     protected void rehash() {
aoqi@0:         Object[] oldObjsTable = objs;
aoqi@0:         int[] oldIntsTable = ints;
aoqi@0:         int oldCapacity = oldObjsTable.length;
aoqi@0:         int newCapacity = oldCapacity << 1;
aoqi@0:         Object[] newObjTable = new Object[newCapacity];
aoqi@0:         int[] newIntTable = new int[newCapacity];
aoqi@0:         int newMask = newCapacity - 1;
aoqi@0:         objs = newObjTable;
aoqi@0:         ints = newIntTable;
aoqi@0:         mask = newMask;
aoqi@0:         num_bindings = 0; // this is recomputed below
aoqi@0:         Object key;
aoqi@0:         for (int i = oldIntsTable.length; --i >= 0;) {
aoqi@0:             key = oldObjsTable[i];
aoqi@0:             if (key != null && key != DELETED)
aoqi@0:                 putAtIndex(key, oldIntsTable[i], lookup(key, hash(key)));
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Removes all mappings from this map.
aoqi@0:      */
aoqi@0:     public void clear() {
aoqi@0:         for (int i = objs.length; --i >= 0;) {
aoqi@0:             objs[i] = null;
aoqi@0:         }
aoqi@0:         num_bindings = 0;
aoqi@0:     }
aoqi@0: }