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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package com.sun.tools.javac.util;

import java.lang.ref.SoftReference;

import com.sun.tools.javac.util.DefinedBy.Api;

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 is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.
/**
 * 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.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  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<>(t));
    }

    
The hash table for names.
/** The hash table for names.
     */
    private NameImpl[] hashes;

    
The shared byte array holding all encountered names.
/** The shared byte array holding all encountered names.
     */
    public byte[] bytes;

    
The mask to be used for hashing
/** The mask to be used for hashing
     */
    private int hashMask;

    
The number of filled bytes in `names'.
/** 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.
/** 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 = ArrayUtils.ensureCapacity(this.bytes, nc + len * 3);
        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;
            names = this.bytes = ArrayUtils.ensureCapacity(names, nc + len);
            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.
/** 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'.
/** 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.
/** 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.
/** Return the hash value of this name.
         */
        @DefinedBy(Api.LANGUAGE_MODEL)
        public int hashCode() {
            return index;
        }

        
Is this name equal to other?
/** Is this name equal to other?
         */
        @DefinedBy(Api.LANGUAGE_MODEL)
        public boolean equals(Object other) {
            if (other instanceof Name)
                return
                    table == ((Name)other).table && index == ((Name) other).getIndex();
            else return false;
        }

    }

}