pool.java

是一款用JAVA 编写的编译器 具有很强的编译功能

/*
 * Copyright 1999-2005 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.tools.javac.jvm;

import java.util.*;

import com.sun.tools.javac.util.*;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.code.Type;

/** An internal structure that corresponds to the constant pool of a classfile.
 *
 *  <p><b>This is NOT part of any API supported by Sun Microsystems.  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 Pool {

    public static final int MAX_ENTRIES = 0xFFFF;
    public static final int MAX_STRING_LENGTH = 0xFFFF;

    /** Index of next constant to be entered.
     */
    int pp;

    /** The initial pool buffer.
     */
    Object[] pool;

    /** A hashtable containing all constants in the pool.
     */
    Map<Object,Integer> indices;

    /** Construct a pool with given number of elements and element array.
     */
    public Pool(int pp, Object[] pool) {
	this.pp = pp;
	this.pool = pool;
	this.indices = new HashMap<Object,Integer>(pool.length);
	for (int i = 1; i < pp; i++) {
	    if (pool[i] != null) indices.put(pool[i], i);
	}
    }

    /** Construct an empty pool.
     */
    public Pool() {
	this(1, new Object[64]);
    }

    /** Return the number of entries in the constant pool.
     */
    public int numEntries() {
	return pp;
    }

    /** Remove everything from this pool.
     */
    public void reset() {
        pp = 1;
	indices.clear();
    }

    /** Double pool buffer in size.
     */
    private void doublePool() {
        Object[] newpool = new Object[pool.length * 2];
        System.arraycopy(pool, 0, newpool, 0, pool.length);
        pool = newpool;
    }

    /** Place an object in the pool, unless it is already there.
     *  If object is a symbol also enter its owner unless the owner is a
     *  package.  Return the object's index in the pool.
     */
    public int put(Object value) {
	if (value instanceof MethodSymbol)
	    value = new Method((MethodSymbol)value);
	else if (value instanceof VarSymbol)
	    value = new Variable((VarSymbol)value);
//	assert !(value instanceof Type.TypeVar);
	Integer index = indices.get(value);
	if (index == null) {
//	    System.err.println("put " + value + " " + value.getClass());//DEBUG
	    index = pp;
	    indices.put(value, index);
            if (pp == pool.length) doublePool();
            pool[pp++] = value;
	    if (value instanceof Long || value instanceof Double) {
		if (pp == pool.length) doublePool();
		pool[pp++] = null;
	    }
	}
	return index.intValue();
    }

    /** Return the given object's index in the pool,
     *  or -1 if object is not in there.
     */
    public int get(Object o) {
	Integer n = indices.get(o);
	return n == null ? -1 : n.intValue();
    }

    static class Method extends DelegatedSymbol {
	MethodSymbol m;
	Method(MethodSymbol m) {
	    super(m);
	    this.m = m;
	}
	public boolean equals(Object other) {
	    if (!(other instanceof Method)) return false;
	    MethodSymbol o = ((Method)other).m;
	    return
		o.name == m.name &&
		o.owner == m.owner &&
		o.type.equals(m.type);
	}
	public int hashCode() {
	    return
		m.name.hashCode() * 33 +
		m.owner.hashCode() * 9 +
		m.type.hashCode();
	}
    }

    static class Variable extends DelegatedSymbol {
	VarSymbol v;
	Variable(VarSymbol v) {
	    super(v);
	    this.v = v;
	}
	public boolean equals(Object other) {
	    if (!(other instanceof Variable)) return false;
	    VarSymbol o = ((Variable)other).v;
	    return
		o.name == v.name &&
		o.owner == v.owner &&
		o.type.equals(v.type);
	}
	public int hashCode() {
	    return
		v.name.hashCode() * 33 +
		v.owner.hashCode() * 9 +
		v.type.hashCode();
	}
    }
}