/*

 * Copyright (c) 1999, 2008, 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

 * or visit www.oracle.com if you need additional information or have any

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 */

package com.sun.tools.javac.util;

import java.lang.ref.SoftReference;

/**

 * Implementation of Name.Table that stores all names in a single shared

 * byte array, expanding it as needed. This avoids the overhead incurred

 * by using an array of bytes for each name.

 *

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class SharedNameTable extends Name.Table {

    // maintain a freelist of recently used name tables for reuse.

    private static List<SoftReference<SharedNameTable>> freelist = List.nil();

    static public synchronized SharedNameTable create(Names names) {

        while (freelist.nonEmpty()) {

            SharedNameTable t = freelist.head.get();

            freelist = freelist.tail;

            if (t != null) {

                return t;

            }

        }

        return new SharedNameTable(names);

    }

    static private synchronized void dispose(SharedNameTable t) {

        freelist = freelist.prepend(new SoftReference<SharedNameTable>(t));

    }

    /** The hash table for names.

     */

    private NameImpl[] hashes;

    /** The shared byte array holding all encountered names.

     */

    public byte[] bytes;

    /** The mask to be used for hashing

     */

    private int hashMask;

    /** The number of filled bytes in `names'.

     */

    private int nc = 0;

    /** Allocator

     *  @param names The main name table

     *  @param hashSize the (constant) size to be used for the hash table

     *                  needs to be a power of two.

     *  @param nameSize the initial size of the name table.

     */

    public SharedNameTable(Names names, int hashSize, int nameSize) {

        super(names);

        hashMask = hashSize - 1;

        hashes = new NameImpl[hashSize];

        bytes = new byte[nameSize];

    }

    public SharedNameTable(Names names) {

        this(names, 0x8000, 0x20000);

    }

    @Override

    public Name fromChars(char[] cs, int start, int len) {

        int nc = this.nc;

        byte[] bytes = this.bytes;

        while (nc + len * 3 >= bytes.length) {

            //          System.err.println("doubling name buffer of length " + names.length + " to fit " + len + " chars");//DEBUG

            byte[] newnames = new byte[bytes.length * 2];

            System.arraycopy(bytes, 0, newnames, 0, bytes.length);

            bytes = this.bytes = newnames;

        }

        int nbytes = Convert.chars2utf(cs, start, bytes, nc, len) - nc;

        int h = hashValue(bytes, nc, nbytes) & hashMask;

        NameImpl n = hashes[h];

        while (n != null &&

                (n.getByteLength() != nbytes ||

                !equals(bytes, n.index, bytes, nc, nbytes))) {

            n = n.next;

        }

        if (n == null) {

            n = new NameImpl(this);

            n.index = nc;

            n.length = nbytes;

            n.next = hashes[h];

            hashes[h] = n;

            this.nc = nc + nbytes;

            if (nbytes == 0) {

                this.nc++;

            }

        }

        return n;

    }

    @Override

    public Name fromUtf(byte[] cs, int start, int len) {

        int h = hashValue(cs, start, len) & hashMask;

        NameImpl n = hashes[h];

        byte[] names = this.bytes;

        while (n != null &&

                (n.getByteLength() != len || !equals(names, n.index, cs, start, len))) {

            n = n.next;

        }

        if (n == null) {

            int nc = this.nc;

            while (nc + len > names.length) {

                //              System.err.println("doubling name buffer of length + " + names.length + " to fit " + len + " bytes");//DEBUG

                byte[] newnames = new byte[names.length * 2];

                System.arraycopy(names, 0, newnames, 0, names.length);

                names = this.bytes = newnames;

            }

            System.arraycopy(cs, start, names, nc, len);

            n = new NameImpl(this);

            n.index = nc;

            n.length = len;

            n.next = hashes[h];

            hashes[h] = n;

            this.nc = nc + len;

            if (len == 0) {

                this.nc++;

            }

        }

        return n;

    }

    @Override

    public void dispose() {

        dispose(this);

    }

    static class NameImpl extends Name {

        /** The next name occupying the same hash bucket.

         */

        NameImpl next;

        /** The index where the bytes of this name are stored in the global name

         *  buffer `byte'.

         */

        int index;

        /** The number of bytes in this name.

         */

        int length;

        NameImpl(SharedNameTable table) {

            super(table);

        }

        @Override

        public int getIndex() {

            return index;

        }

        @Override

        public int getByteLength() {

            return length;

        }

        @Override

        public byte getByteAt(int i) {

            return getByteArray()[index + i];

        }

        @Override

        public byte[] getByteArray() {

            return ((SharedNameTable) table).bytes;

        }

        @Override

        public int getByteOffset() {

            return index;

        }

        /** Return the hash value of this name.

         */

        public int hashCode() {

            return index;

        }

        /** Is this name equal to other?

         */

        public boolean equals(Object other) {

            if (other instanceof Name)

                return

                    table == ((Name)other).table && index == ((Name) other).getIndex();

            else return false;

        }

    }

}