compiler/org/eclipse/jdt/internal/compiler/ast/WhileStatement.java

package org.eclipse.jdt.internal.compiler.ast;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */
import org.eclipse.jdt.internal.compiler.IAbstractSyntaxTreeVisitor;
import org.eclipse.jdt.internal.compiler.impl.*;
import org.eclipse.jdt.internal.compiler.codegen.*;
import org.eclipse.jdt.internal.compiler.flow.*;
import org.eclipse.jdt.internal.compiler.lookup.*;

public class WhileStatement extends Statement {
	public Expression condition;
	public Statement action;

	private Label breakLabel, continueLabel;

	int preCondInitStateIndex = -1;
	int condIfTrueInitStateIndex = -1;
	int mergedInitStateIndex = -1;	
public WhileStatement(Expression condition, Statement action,int s,int e) {
	this.condition = condition;
	this.action = action;
	sourceStart = s;
	sourceEnd = e;
}
public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
	breakLabel = new Label();
	continueLabel = new Label();

	preCondInitStateIndex = currentScope.methodScope().recordInitializationStates(flowInfo);
	LoopingFlowContext condLoopContext;
	FlowInfo postCondInfo = condition.analyseCode(
		currentScope,
		(condLoopContext = new LoopingFlowContext(flowContext, this, null, null, currentScope)),
		flowInfo);

	LoopingFlowContext loopingContext;
	if ((action == null) || action.isEmptyBlock()) {
		condLoopContext.complainOnFinalAssignmentsInLoop(currentScope, postCondInfo);
		if ((condition.constant != NotAConstant) && (condition.constant.booleanValue() == true)) {
			return FlowInfo.DeadEnd;
		} else {
			FlowInfo mergedInfo = postCondInfo.initsWhenFalse().unconditionalInits();
			mergedInitStateIndex = currentScope.methodScope().recordInitializationStates(mergedInfo);
			return mergedInfo;
		}
	} else {
		// in case the condition was inlined to false, record the fact that there is no way to reach any 
		// statement inside the looping action
		loopingContext = new LoopingFlowContext(flowContext, this, breakLabel, continueLabel, currentScope);
		FlowInfo actionInfo =
			((condition.constant != Constant.NotAConstant) && (condition.constant.booleanValue() == false)) ?
				FlowInfo.DeadEnd :
				postCondInfo.initsWhenTrue().copy();
				
		// for computing local var attributes
		condIfTrueInitStateIndex = currentScope.methodScope().recordInitializationStates(postCondInfo.initsWhenTrue());
		
		if (!actionInfo.complainIfUnreachable(action, currentScope)){
			actionInfo = action.analyseCode(currentScope, loopingContext, actionInfo);
		}

		// code generation can be optimized when no need to continue in the loop
		if (((actionInfo == FlowInfo.DeadEnd) || actionInfo.isFakeReachable())
			&& ((loopingContext.initsOnContinue == FlowInfo.DeadEnd) || loopingContext.initsOnContinue.isFakeReachable())){
				continueLabel = null;
		} else {
			condLoopContext.complainOnFinalAssignmentsInLoop(currentScope, postCondInfo);
			loopingContext.complainOnFinalAssignmentsInLoop(currentScope, actionInfo);
		}
	}

	// infinite loop
	FlowInfo mergedInfo;
	if ((condition.constant != Constant.NotAConstant) && (condition.constant.booleanValue() == true)) {
		mergedInitStateIndex = currentScope.methodScope().recordInitializationStates(mergedInfo = loopingContext.initsOnBreak);
		return mergedInfo;
	}

	// end of loop: either condition false or break
	mergedInfo = postCondInfo.initsWhenFalse().unconditionalInits().mergedWith(loopingContext.initsOnBreak);
	mergedInitStateIndex = currentScope.methodScope().recordInitializationStates(mergedInfo);
	return mergedInfo;
}
/**
 * While code generation
 *
 * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 */ 
public void generateCode(BlockScope currentScope, CodeStream codeStream) {
	if ((bits & IsReachableMASK) == 0) {
		return;
	}
	int pc = codeStream.position;
	breakLabel.codeStream = codeStream;

	// generate condition
	if (continueLabel == null){
		// no need to reverse condition
		if (condition.constant == NotAConstant){
			condition.generateOptimizedBoolean(currentScope, codeStream, null, breakLabel, true);
		}
	} else {
		continueLabel.codeStream = codeStream;
		if (!(((condition.constant != NotAConstant) && (condition.constant.booleanValue() == true)) || (action == null) || action.isEmptyBlock())){
			int jumpPC = codeStream.position;
			codeStream.goto_(continueLabel);
			codeStream.recordPositionsFrom(jumpPC, condition);
		}
	}
	// generate the action
	Label actionLabel;
	(actionLabel = new Label(codeStream)).place();
	if (action != null){
		// Required to fix 1PR0XVS: LFRE:WINNT - Compiler: variable table for method appears incorrect
		if (condIfTrueInitStateIndex != -1){ // insert all locals initialized inside the condition into the action generated prior to the condition
			codeStream.addDefinitelyAssignedVariables(currentScope, condIfTrueInitStateIndex);
		}
		action.generateCode(currentScope, codeStream);
		// May loose some local variable initializations : affecting the local variable attributes
		if (preCondInitStateIndex != -1) {
			codeStream.removeNotDefinitelyAssignedVariables(currentScope, preCondInitStateIndex);
		}	
		
	}
	// output condition and branch back to the beginning of the repeated action
	if (continueLabel != null){
		continueLabel.place();
		condition.generateOptimizedBoolean(currentScope, codeStream, actionLabel, null, true);
	}
	breakLabel.place();

	// May loose some local variable initializations : affecting the local variable attributes
	if (mergedInitStateIndex != -1) {
		codeStream.removeNotDefinitelyAssignedVariables(currentScope, mergedInitStateIndex);
	}
	codeStream.recordPositionsFrom(pc, this);
}
public void resolve(BlockScope scope) {
	TypeBinding type = condition.resolveTypeExpecting(scope, BooleanBinding);
	condition.implicitWidening(type, type);
	if (action != null)
		action.resolve(scope);
}
public String toString(int tab){
	/* slow code */

	String s = tabString(tab) ;
	s = s + "while ("/*nonNLS*/ + condition.toStringExpression() + ")"/*nonNLS*/;
	if (action == null)
		s = s + " {} ;"/*nonNLS*/;
	else
		if (action instanceof Block)
			s = s + "\n"/*nonNLS*/ + action.toString(tab+1) ;
		else
			s = s + " {\n"/*nonNLS*/ + action.toString(tab+1) + "}"/*nonNLS*/ ;
	return s;}
public void traverse(IAbstractSyntaxTreeVisitor visitor, BlockScope blockScope) {
	if (visitor.visit(this, blockScope)) {
		condition.traverse(visitor, blockScope);
		if (action != null)
			action.traverse(visitor, blockScope);
	}
	visitor.endVisit(this, blockScope);
}
}