/*

 * Copyright (c) 2004, 2012, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package sun.util;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.AbstractMap;

import java.util.AbstractSet;

import java.util.NoSuchElementException;

/**

 * A precomputed hash map.

 *

 * <p> Subclasses of this class are of the following form:

 *

 * <blockquote><pre>

 * class FooMap

 *     extends sun.util.PreHashedMap<String>

 * {

 *

 *     private FooMap() {

 *         super(ROWS, SIZE, SHIFT, MASK);

 *     }

 *

 *     protected void init(Object[] ht) {

 *         ht[0] = new Object[] { "key-1", value_1 };

 *         ht[1] = new Object[] { "key-2", value_2,

 *                      new Object { "key-3", value_3 } };

 *         ...

 *     }

 *

 * }</pre></blockquote>

 *

 * <p> The {@code init} method is invoked by the {@code PreHashedMap}

 * constructor with an object array long enough for the map's rows.  The method

 * must construct the hash chain for each row and store it in the appropriate

 * element of the array.

 *

 * <p> Each entry in the map is represented by a unique hash-chain node.  The

 * final node of a hash chain is a two-element object array whose first element

 * is the entry's key and whose second element is the entry's value.  A

 * non-final node of a hash chain is a three-element object array whose first

 * two elements are the entry's key and value and whose third element is the

 * next node in the chain.

 *

 * <p> Instances of this class are mutable and are not safe for concurrent

 * access.  They may be made immutable and thread-safe via the appropriate

 * methods in the {@link java.util.Collections} utility class.

 *

 * <p> In the JDK build, subclasses of this class are typically created via the

 * {@code Hasher} program in the {@code make/tools/Hasher} directory.

 *

 * @author Mark Reinhold

 * @since 1.5

 *

 * @see java.util.AbstractMap

 */

public abstract class PreHashedMap<V>

    extends AbstractMap<String,V>

{

    private final int rows;

    private final int size;

    private final int shift;

    private final int mask;

    private final Object[] ht;

    /**

     * Creates a new map.

     *

     * <p> This constructor invokes the {@link #init init} method, passing it a

     * newly-constructed row array that is {@code rows} elements long.

     *

     * @param rows

     *        The number of rows in the map

     * @param size

     *        The number of entries in the map

     * @param shift

     *        The value by which hash codes are right-shifted

     * @param mask

     *        The value with which hash codes are masked after being shifted

     */

    protected PreHashedMap(int rows, int size, int shift, int mask) {

        this.rows = rows;

        this.size = size;

        this.shift = shift;

        this.mask = mask;

        this.ht = new Object[rows];

        init(ht);

    }

    /**

     * Initializes this map.

     *

     * <p> This method must construct the map's hash chains and store them into

     * the appropriate elements of the given hash-table row array.

     *

     * @param ht The row array to be initialized

     */

    protected abstract void init(Object[] ht);

    @SuppressWarnings("unchecked")

    private V toV(Object x) {

        return (V)x;

    }

    public V get(Object k) {

        int h = (k.hashCode() >> shift) & mask;

        Object[] a = (Object[])ht[h];

        if (a == null) return null;

        for (;;) {

            if (a[0].equals(k))

                return toV(a[1]);

            if (a.length < 3)

                return null;

            a = (Object[])a[2];

        }

    }

    /**

     * @throws UnsupportedOperationException

     *         If the given key is not part of this map's initial key set

     */

    public V put(String k, V v) {

        int h = (k.hashCode() >> shift) & mask;

        Object[] a = (Object[])ht[h];

        if (a == null)

            throw new UnsupportedOperationException(k);

        for (;;) {

            if (a[0].equals(k)) {

                V ov = toV(a[1]);

                a[1] = v;

                return ov;

            }

            if (a.length < 3)

                throw new UnsupportedOperationException(k);

            a = (Object[])a[2];

        }

    }

    public Set<String> keySet() {

        return new AbstractSet<> () {

            public int size() {

                return size;

            }

            public Iterator<String> iterator() {

                return new Iterator<>() {

                    private int i = -1;

                    Object[] a = null;

                    String cur = null;

                    private boolean findNext() {

                        if (a != null) {

                            if (a.length == 3) {

                                a = (Object[])a[2];

                                cur = (String)a[0];

                                return true;

                            }

                            i++;

                            a = null;

                        }

                        cur = null;

                        if (i >= rows)

                            return false;

                        if (i < 0 || ht[i] == null) {

                            do {

                                if (++i >= rows)

                                    return false;

                            } while (ht[i] == null);

                        }

                        a = (Object[])ht[i];

                        cur = (String)a[0];

                        return true;

                    }

                    public boolean hasNext() {

                        if (cur != null)

                            return true;

                        return findNext();

                    }

                    public String next() {

                        if (cur == null) {

                            if (!findNext())

                                throw new NoSuchElementException();

                        }

                        String s = cur;

                        cur = null;

                        return s;

                    }

                    public void remove() {

                        throw new UnsupportedOperationException();

                    }

                };

            }

        };

    }

    public Set<Map.Entry<String,V>> entrySet() {

        return new AbstractSet<Map.Entry<String,V>> () {

            public int size() {

                return size;

            }

            public Iterator<Map.Entry<String,V>> iterator() {

                return new Iterator<Map.Entry<String,V>>() {

                    final Iterator<String> i = keySet().iterator();

                    public boolean hasNext() {

                        return i.hasNext();

                    }

                    public Map.Entry<String,V> next() {

                        return new Map.Entry<String,V>() {

                            String k = i.next();

                            public String getKey() { return k; }

                            public V getValue() { return get(k); }

                            public int hashCode() {

                                V v = get(k);

                                return (k.hashCode()

                                        + (v == null

                                           ? 0

                                           : v.hashCode()));

                            }

                            public boolean equals(Object ob) {

                                if (ob == this)

                                    return true;

                                if (!(ob instanceof Map.Entry))

                                    return false;

                                Map.Entry<?,?> that = (Map.Entry<?,?>)ob;

                                return ((this.getKey() == null

                                         ? that.getKey() == null

                                         : this.getKey()

                                               .equals(that.getKey()))

                                        &&

                                        (this.getValue() == null

                                         ? that.getValue() == null

                                         : this.getValue()

                                               .equals(that.getValue())));

                            }

                            public V setValue(V v) {

                                throw new UnsupportedOperationException();

                            }

                        };

                    }

                    public void remove() {

                        throw new UnsupportedOperationException();

                    }

                };

            }

        };

    }

}