predicate.java

java1.6众多例子参考

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: Predicate.java,v 1.2.4.1 2005/09/12 11:02:18 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.ArrayList;

import com.sun.org.apache.bcel.internal.classfile.Field;
import com.sun.org.apache.bcel.internal.generic.ASTORE;
import com.sun.org.apache.bcel.internal.generic.CHECKCAST;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.GETFIELD;
import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.LocalVariableGen;
import com.sun.org.apache.bcel.internal.generic.NEW;
import com.sun.org.apache.bcel.internal.generic.PUSH;
import com.sun.org.apache.bcel.internal.generic.PUTFIELD;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.BooleanType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.FilterGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.IntType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NumberType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ReferenceType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ResultTreeType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TestGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;
import com.sun.org.apache.xalan.internal.xsltc.runtime.Operators;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 */
final class Predicate extends Expression implements Closure {

    /**
     * The predicate's expression.
     */
    private Expression _exp = null; 
    
    /**
     * This flag indicates if optimizations are turned on. The 
     * method <code>dontOptimize()</code> can be called to turn
     * optimizations off.
     */
    private boolean _canOptimize = true;
    
    /**
     * Flag indicatig if the nth position optimization is on. It
     * is set in <code>typeCheck()</code>.
     */
    private boolean _nthPositionFilter = false;
        
    /**
     * Flag indicatig if the nth position descendant is on. It
     * is set in <code>typeCheck()</code>.
     */
    private boolean _nthDescendant = false;

    /**
     * Cached node type of the expression that owns this predicate.
     */
    int _ptype = -1;

    /**
     * Name of the inner class.
     */
    private String _className = null;
    
    /**
     * List of variables in closure.
     */
    private ArrayList _closureVars = null;
    
    /**
     * Reference to parent closure.
     */
    private Closure _parentClosure = null;

    /**
     * Cached value of method <code>getCompareValue()</code>.
     */
    private Expression _value = null;
    
    /**
     * Cached value of method <code>getCompareValue()</code>.
     */
    private Step _step = null;

    /**
     * Initializes a predicate. 
     */
    public Predicate(Expression exp) {
        _exp = exp;
        _exp.setParent(this);

    }

    /** 
     * Set the parser for this expression.
     */
    public void setParser(Parser parser) {
	super.setParser(parser);
	_exp.setParser(parser);
    }

    /**
     * Returns a boolean value indicating if the nth position optimization
     * is on. Must be call after type checking!
     */
    public boolean isNthPositionFilter() {
	return _nthPositionFilter;
    }

    /**
     * Returns a boolean value indicating if the nth descendant optimization
     * is on. Must be call after type checking!
     */
    public boolean isNthDescendant() {
	return _nthDescendant;
    }

    /**
     * Turns off all optimizations for this predicate.
     */
    public void dontOptimize() {
	_canOptimize = false;
    }
    
    /**
     * Returns true if the expression in this predicate contains a call 
     * to position().
     */
    public boolean hasPositionCall() {
	return _exp.hasPositionCall();
    }

    /**
     * Returns true if the expression in this predicate contains a call 
     * to last().
     */
    public boolean hasLastCall() {
	return _exp.hasLastCall();
    }

    // -- Begin Closure interface --------------------

    /**
     * Returns true if this closure is compiled in an inner class (i.e.
     * if this is a real closure).
     */
    public boolean inInnerClass() {
	return (_className != null);
    }

    /**
     * Returns a reference to its parent closure or null if outermost.
     */
    public Closure getParentClosure() {
	if (_parentClosure == null) {
	    SyntaxTreeNode node = getParent();
	    do {
		if (node instanceof Closure) {
		    _parentClosure = (Closure) node;
		    break;
		}
		if (node instanceof TopLevelElement) {
		    break;	// way up in the tree
		}
		node = node.getParent();
	    } while (node != null);
	}
	return _parentClosure;
    }

    /**
     * Returns the name of the auxiliary class or null if this predicate 
     * is compiled inside the Translet.
     */
    public String getInnerClassName() {
	return _className;
    }

    /**
     * Add new variable to the closure.
     */
    public void addVariable(VariableRefBase variableRef) {
	if (_closureVars == null) {
	    _closureVars = new ArrayList();
	}

	// Only one reference per variable
	if (!_closureVars.contains(variableRef)) {
	    _closureVars.add(variableRef);

	    // Add variable to parent closure as well
	    Closure parentClosure = getParentClosure();
	    if (parentClosure != null) {
		parentClosure.addVariable(variableRef);
	    }
	}
    }

    // -- End Closure interface ----------------------

    /**
     * Returns the node type of the expression owning this predicate. The
     * return value is cached in <code>_ptype</code>.
     */
    public int getPosType() {
	if (_ptype == -1) {
	    SyntaxTreeNode parent = getParent();
	    if (parent instanceof StepPattern) {
		_ptype = ((StepPattern)parent).getNodeType();
	    }
	    else if (parent instanceof AbsoluteLocationPath) {
		AbsoluteLocationPath path = (AbsoluteLocationPath)parent;
		Expression exp = path.getPath();
		if (exp instanceof Step) {
		    _ptype = ((Step)exp).getNodeType();
		}
	    }
	    else if (parent instanceof VariableRefBase) {
		final VariableRefBase ref = (VariableRefBase)parent;
		final VariableBase var = ref.getVariable();
		final Expression exp = var.getExpression();
		if (exp instanceof Step) {
		    _ptype = ((Step)exp).getNodeType();
		}
	    }
	    else if (parent instanceof Step) {
		_ptype = ((Step)parent).getNodeType();
	    }
	}
	return _ptype;
    }

    public boolean parentIsPattern() {
	return (getParent() instanceof Pattern);
    }

    public Expression getExpr() {
	return _exp;
    }

    public String toString() {
        return "pred(" + _exp + ')';
    }
	
    /**
     * Type check a predicate expression. If the type of the expression is 
     * number convert it to boolean by adding a comparison with position().
     * Note that if the expression is a parameter, we cannot distinguish
     * at compile time if its type is number or not. Hence, expressions of 
     * reference type are always converted to booleans.
     *
     * This method may be called twice, before and after calling
     * <code>dontOptimize()</code>. If so, the second time it should honor
     * the new value of <code>_canOptimize</code>.
     */
    public Type typeCheck(SymbolTable stable) throws TypeCheckError {        
	Type texp = _exp.typeCheck(stable);

	// We need explicit type information for reference types - no good!
	if (texp instanceof ReferenceType) {
	    _exp = new CastExpr(_exp, texp = Type.Real);
	}

	// A result tree fragment should not be cast directly to a number type,
	// but rather to a boolean value, and then to a numer (0 or 1).
	// Ref. section 11.2 of the XSLT 1.0 spec
	if (texp instanceof ResultTreeType) {
	    _exp = new CastExpr(_exp, Type.Boolean);
	    _exp = new CastExpr(_exp, Type.Real);
	    texp = _exp.typeCheck(stable);
	}

	// Numerical types will be converted to a position filter
	if (texp instanceof NumberType) {
	    // Cast any numerical types to an integer
	    if (texp instanceof IntType == false) {
		_exp = new CastExpr(_exp, Type.Int);
	    }
                    
            if (_canOptimize) {
                // Nth position optimization. Expression must not depend on context
                _nthPositionFilter = 
                    !_exp.hasLastCall() && !_exp.hasPositionCall();
                
                // _nthDescendant optimization - only if _nthPositionFilter is on