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EqualityExpr.javaAPI DocJava SE 5 API11463Fri Aug 26 14:55:34 BST 2005com.sun.org.apache.xalan.internal.xsltc.compiler

EqualityExpr

public final class EqualityExpr extends Expression implements Operators
author
Jacek Ambroziak
author
Santiago Pericas-Geertsen
author
Morten Jorgensen
author
Erwin Bolwidt

Fields Summary
private final int
_op
private Expression
_left
private Expression
_right
Constructors Summary
public EqualityExpr(int op, Expression left, Expression right)

	_op = op;
	(_left = left).setParent(this);
	(_right = right).setParent(this);
Methods Summary
public com.sun.org.apache.xalan.internal.xsltc.compiler.ExpressiongetLeft()

	return _left;
public booleangetOp()

	return (_op != Operators.NE);
public com.sun.org.apache.xalan.internal.xsltc.compiler.ExpressiongetRight()

	return _right;
public booleanhasLastCall()

	if (_left.hasLastCall()) return true;
	if (_right.hasLastCall()) return true;
	return false;
public booleanhasPositionCall()
Returns true if this expressions contains a call to position(). This is needed for context changes in node steps containing multiple predicates.

	if (_left.hasPositionCall()) return true;
	if (_right.hasPositionCall()) return true;
	return false;
public voidsetParser(com.sun.org.apache.xalan.internal.xsltc.compiler.Parser parser)

	super.setParser(parser);
	_left.setParser(parser);
	_right.setParser(parser);
private voidswapArguments()

	final Expression temp = _left;
	_left = _right;
	_right = temp;
public java.lang.StringtoString()

	return Operators.names[_op] + '(" + _left + ", " + _right + ')";
public voidtranslate(com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator classGen, com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator methodGen)

	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();

	final Type tleft = _left.getType();
	Type tright = _right.getType();

	if (tleft instanceof BooleanType || tleft instanceof NumberType) {
	    translateDesynthesized(classGen, methodGen);
	    synthesize(classGen, methodGen);
	    return;
	}

	if (tleft instanceof StringType) {
	    final int equals = cpg.addMethodref(STRING_CLASS,
						"equals",
						"(" + OBJECT_SIG +")Z");
	    _left.translate(classGen, methodGen);
	    _right.translate(classGen, methodGen);
	    il.append(new INVOKEVIRTUAL(equals));

	    if (_op == Operators.NE) {
		il.append(ICONST_1);
		il.append(IXOR);			// not x <-> x xor 1
	    }
	    return;
	}

	BranchHandle truec, falsec;
	
	if (tleft instanceof ResultTreeType) {
	    if (tright instanceof BooleanType) {
		_right.translate(classGen, methodGen);
		if (_op == Operators.NE) {
		    il.append(ICONST_1);
		    il.append(IXOR); // not x <-> x xor 1
		}
		return;
	    }

	    if (tright instanceof RealType) {
		_left.translate(classGen, methodGen);
		tleft.translateTo(classGen, methodGen, Type.Real);
		_right.translate(classGen, methodGen);

		il.append(DCMPG);
		falsec = il.append(_op == Operators.EQ ? 
				   (BranchInstruction) new IFNE(null) : 
				   (BranchInstruction) new IFEQ(null));
		il.append(ICONST_1);
		truec = il.append(new GOTO(null));
		falsec.setTarget(il.append(ICONST_0));
		truec.setTarget(il.append(NOP));
		return;
	    }

	    // Next, result-tree/string and result-tree/result-tree comparisons

	    _left.translate(classGen, methodGen);
	    tleft.translateTo(classGen, methodGen, Type.String);
	    _right.translate(classGen, methodGen);

	    if (tright instanceof ResultTreeType) {
		tright.translateTo(classGen, methodGen, Type.String);
	    }

	    final int equals = cpg.addMethodref(STRING_CLASS,
						"equals",
						"(" +OBJECT_SIG+ ")Z");
	    il.append(new INVOKEVIRTUAL(equals));

	    if (_op == Operators.NE) {
		il.append(ICONST_1);
		il.append(IXOR);			// not x <-> x xor 1
	    }
	    return;
	}

	if (tleft instanceof NodeSetType && tright instanceof BooleanType) {
	    _left.translate(classGen, methodGen);
	    _left.startIterator(classGen, methodGen);
	    Type.NodeSet.translateTo(classGen, methodGen, Type.Boolean);
	    _right.translate(classGen, methodGen);

	    il.append(IXOR); // x != y <-> x xor y
	    if (_op == EQ) {
		il.append(ICONST_1);
		il.append(IXOR); // not x <-> x xor 1
	    }
	    return;
	}

	if (tleft instanceof NodeSetType && tright instanceof StringType) {
	    _left.translate(classGen, methodGen);
	    _left.startIterator(classGen, methodGen); // needed ?
	    _right.translate(classGen, methodGen);
	    il.append(new PUSH(cpg, _op));
	    il.append(methodGen.loadDOM());
	    final int cmp = cpg.addMethodref(BASIS_LIBRARY_CLASS,
					     "compare",
					     "("
					     + tleft.toSignature() 
					     + tright.toSignature()
					     + "I"
					     + DOM_INTF_SIG
					     + ")Z");
	    il.append(new INVOKESTATIC(cmp));
	    return;
	}

	// Next, node-set/t for t in {real, string, node-set, result-tree}
	_left.translate(classGen, methodGen);
	_left.startIterator(classGen, methodGen);
	_right.translate(classGen, methodGen);
	_right.startIterator(classGen, methodGen);

	// Cast a result tree to a string to use an existing compare
	if (tright instanceof ResultTreeType) {
	    tright.translateTo(classGen, methodGen, Type.String);	
	    tright = Type.String;
	}

	// Call the appropriate compare() from the BasisLibrary
	il.append(new PUSH(cpg, _op));
	il.append(methodGen.loadDOM());

	final int compare = cpg.addMethodref(BASIS_LIBRARY_CLASS,
					     "compare",
					     "("
					     + tleft.toSignature() 
					     + tright.toSignature()
					     + "I"
					     + DOM_INTF_SIG
					     + ")Z");
	il.append(new INVOKESTATIC(compare));
public voidtranslateDesynthesized(com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator classGen, com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator methodGen)

	final Type tleft = _left.getType();
	final InstructionList il = methodGen.getInstructionList();

	if (tleft instanceof BooleanType) {
	    _left.translate(classGen, methodGen);
	    _right.translate(classGen, methodGen);
	    _falseList.add(il.append(_op == Operators.EQ ? 
				     (BranchInstruction)new IF_ICMPNE(null) :
				     (BranchInstruction)new IF_ICMPEQ(null)));
	}
	else if (tleft instanceof NumberType) {
	    _left.translate(classGen, methodGen);
	    _right.translate(classGen, methodGen);

	    if (tleft instanceof RealType) {
		il.append(DCMPG);
		_falseList.add(il.append(_op == Operators.EQ ? 
					 (BranchInstruction)new IFNE(null) : 
					 (BranchInstruction)new IFEQ(null)));
	    }
	    else {
		_falseList.add(il.append(_op == Operators.EQ ? 
					 (BranchInstruction)new IF_ICMPNE(null) :
					 (BranchInstruction)new IF_ICMPEQ(null)));
	    }
	}
	else {
	    translate(classGen, methodGen);
	    desynthesize(classGen, methodGen);
	}
public com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypetypeCheck(com.sun.org.apache.xalan.internal.xsltc.compiler.SymbolTable stable)
Typing rules: see XSLT Reference by M. Kay page 345.

	final Type tleft = _left.typeCheck(stable); 
	final Type tright = _right.typeCheck(stable);

	if (tleft.isSimple() && tright.isSimple()) {
	    if (tleft != tright) {
		if (tleft instanceof BooleanType) {
		    _right = new CastExpr(_right, Type.Boolean);
		}
		else if (tright instanceof BooleanType) {
		    _left = new CastExpr(_left, Type.Boolean);
		}
		else if (tleft instanceof NumberType || 
			 tright instanceof NumberType) {
		    _left = new CastExpr(_left, Type.Real);
		    _right = new CastExpr(_right, Type.Real);
		}
		else {		// both compared as strings
		    _left = new CastExpr(_left,   Type.String);
		    _right = new CastExpr(_right, Type.String);
		}
	    }
	}
	else if (tleft instanceof ReferenceType) {
	    _right = new CastExpr(_right, Type.Reference);
	}
	else if (tright instanceof ReferenceType) {
	    _left = new CastExpr(_left, Type.Reference);
	}
	// the following 2 cases optimize @attr|.|.. = 'string'
	else if (tleft instanceof NodeType && tright == Type.String) {
	    _left = new CastExpr(_left, Type.String);
	}
	else if (tleft == Type.String && tright instanceof NodeType) {
	    _right = new CastExpr(_right, Type.String);
	}
	// optimize node/node
	else if (tleft instanceof NodeType && tright instanceof NodeType) {
	    _left = new CastExpr(_left, Type.String);
	    _right = new CastExpr(_right, Type.String);
	}
	else if (tleft instanceof NodeType && tright instanceof NodeSetType) {
	    // compare(Node, NodeSet) will be invoked
	}
	else if (tleft instanceof NodeSetType && tright instanceof NodeType) {
	    swapArguments();	// for compare(Node, NodeSet)
	}
	else {	
	    // At least one argument is of type node, node-set or result-tree

	    // Promote an expression of type node to node-set
	    if (tleft instanceof NodeType) {
		_left = new CastExpr(_left, Type.NodeSet);
	    }
	    if (tright instanceof NodeType) {
		_right = new CastExpr(_right, Type.NodeSet);
	    }

	    // If one arg is a node-set then make it the left one
	    if (tleft.isSimple() ||
		tleft instanceof ResultTreeType &&
		tright instanceof NodeSetType) {
		swapArguments();
	    }

	    // Promote integers to doubles to have fewer compares
	    if (_right.getType() instanceof IntType) {
		_right = new CastExpr(_right, Type.Real);
	    }
	}
	return _type = Type.Boolean;