/*
* 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: LogicalExpr.java,v 1.14 2004/02/16 22:24:28 minchau Exp $
*/
package org.apache.xalan.xsltc.compiler;
import org.apache.bcel.generic.GOTO;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InstructionList;
import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
import org.apache.xalan.xsltc.compiler.util.MethodType;
import org.apache.xalan.xsltc.compiler.util.Type;
import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
/**
* @author Jacek Ambroziak
* @author Santiago Pericas-Geertsen
* @author Morten Jorgensen
*/
final class LogicalExpr extends Expression {
public static final int OR = 0;
public static final int AND = 1;
private final int _op; // operator
private Expression _left; // first operand
private Expression _right; // second operand
private static final String[] Ops = { "or", "and" };
/**
* Creates a new logical expression - either OR or AND. Note that the
* left- and right-hand side expressions can also be logical expressions,
* thus creating logical trees representing structures such as
* (a and (b or c) and d), etc...
*/
public LogicalExpr(int op, Expression left, Expression right) {
_op = op;
(_left = left).setParent(this);
(_right = right).setParent(this);
}
/**
* Returns true if this expressions contains a call to position(). This is
* needed for context changes in node steps containing multiple predicates.
*/
public boolean hasPositionCall() {
return (_left.hasPositionCall() || _right.hasPositionCall());
}
/**
* Returns true if this expressions contains a call to last()
*/
public boolean hasLastCall() {
return (_left.hasLastCall() || _right.hasLastCall());
}
/**
* Returns an object representing the compile-time evaluation
* of an expression. We are only using this for function-available
* and element-available at this time.
*/
public Object evaluateAtCompileTime() {
final Object leftb = _left.evaluateAtCompileTime();
final Object rightb = _right.evaluateAtCompileTime();
// Return null if we can't evaluate at compile time
if (leftb == null || rightb == null) {
return null;
}
if (_op == AND) {
return (leftb == Boolean.TRUE && rightb == Boolean.TRUE) ?
Boolean.TRUE : Boolean.FALSE;
}
else {
return (leftb == Boolean.TRUE || rightb == Boolean.TRUE) ?
Boolean.TRUE : Boolean.FALSE;
}
}
/**
* Returns this logical expression's operator - OR or AND represented
* by 0 and 1 respectively.
*/
public int getOp() {
return(_op);
}
/**
* Override the SyntaxTreeNode.setParser() method to make sure that the
* parser is set for sub-expressions
*/
public void setParser(Parser parser) {
super.setParser(parser);
_left.setParser(parser);
_right.setParser(parser);
}
/**
* Returns a string describing this expression
*/
public String toString() {
return Ops[_op] + '(' + _left + ", " + _right + ')';
}
/**
* Type-check this expression, and possibly child expressions.
*/
public Type typeCheck(SymbolTable stable) throws TypeCheckError {
// Get the left and right operand types
Type tleft = _left.typeCheck(stable);
Type tright = _right.typeCheck(stable);
// Check if the operator supports the two operand types
MethodType wantType = new MethodType(Type.Void, tleft, tright);
MethodType haveType = lookupPrimop(stable, Ops[_op], wantType);
// Yes, the operation is supported
if (haveType != null) {
// Check if left-hand side operand must be type casted
Type arg1 = (Type)haveType.argsType().elementAt(0);
if (!arg1.identicalTo(tleft))
_left = new CastExpr(_left, arg1);
// Check if right-hand side operand must be type casted
Type arg2 = (Type) haveType.argsType().elementAt(1);
if (!arg2.identicalTo(tright))
_right = new CastExpr(_right, arg1);
// Return the result type for the operator we will use
return _type = haveType.resultType();
}
throw new TypeCheckError(this);
}
/**
* Compile the expression - leave boolean expression on stack
*/
public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
translateDesynthesized(classGen, methodGen);
synthesize(classGen, methodGen);
}
/**
* Compile expression and update true/false-lists
*/
public void translateDesynthesized(ClassGenerator classGen,
MethodGenerator methodGen) {
final InstructionList il = methodGen.getInstructionList();
final SyntaxTreeNode parent = getParent();
// Compile AND-expression
if (_op == AND) {
// Translate left hand side - must be true
_left.translateDesynthesized(classGen, methodGen);
// Need this for chaining any OR-expression children
InstructionHandle middle = il.append(NOP);
// Translate left right side - must be true
_right.translateDesynthesized(classGen, methodGen);
// Need this for chaining any OR-expression children
InstructionHandle after = il.append(NOP);
// Append child expression false-lists to our false-list
_falseList.append(_right._falseList.append(_left._falseList));
// Special case for OR-expression as a left child of AND.
// The true-list of OR must point to second clause of AND.
if ((_left instanceof LogicalExpr) &&
(((LogicalExpr)_left).getOp() == OR)) {
_left.backPatchTrueList(middle);
}
else if (_left instanceof NotCall) {
_left.backPatchTrueList(middle);
}
else {
_trueList.append(_left._trueList);
}
// Special case for OR-expression as a right child of AND
// The true-list of OR must point to true-list of AND.
if ((_right instanceof LogicalExpr) &&
(((LogicalExpr)_right).getOp() == OR)) {
_right.backPatchTrueList(after);
}
else if (_right instanceof NotCall) {
_right.backPatchTrueList(after);
}
else {
_trueList.append(_right._trueList);
}
}
// Compile OR-expression
else {
// Translate left-hand side expression and produce true/false list
_left.translateDesynthesized(classGen, methodGen);
// This GOTO is used to skip over the code for the last test
// in the case where the the first test succeeds
InstructionHandle ih = il.append(new GOTO(null));
// Translate right-hand side expression and produce true/false list
_right.translateDesynthesized(classGen, methodGen);
_left._trueList.backPatch(ih);
_left._falseList.backPatch(ih.getNext());
_falseList.append(_right._falseList);
_trueList.add(ih).append(_right._trueList);
}
}
}