com.sun.tools.javac.util.SharedNameTable Maven / Gradle / Ivy
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/*
* Copyright (c) 1999, 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
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 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.
*/
public class SharedNameTable extends Name.Table {
// maintain a freelist of recently used name tables for reuse.
private static List> 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.
*/
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 = 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.
*/
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;
}
}
}