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/*
* Fernflower - The Analytical Java Decompiler
* http://www.reversed-java.com
*
* (C) 2008 - 2010, Stiver
*
* This software is NEITHER public domain NOR free software
* as per GNU License. See license.txt for more details.
*
* This software is distributed WITHOUT ANY WARRANTY; without
* even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE.
*/
package de.fernflower.modules.decompiler;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Set;
import de.fernflower.modules.decompiler.stats.DoStatement;
import de.fernflower.modules.decompiler.stats.IfStatement;
import de.fernflower.modules.decompiler.stats.SequenceStatement;
import de.fernflower.modules.decompiler.stats.Statement;
public class LoopExtractHelper {
public static boolean extractLoops(Statement root) {
boolean res = (extractLoopsRec(root) != 0);
if(res) {
SequenceHelper.condenseSequences(root);
}
return res;
}
private static int extractLoopsRec(Statement stat) {
boolean res = false;
for(;;) {
boolean updated = false;
for(Statement st: stat.getStats()) {
int extr = extractLoopsRec(st);
res |= (extr != 0);
if(extr == 2) {
updated = true;
break;
}
}
if(!updated) {
break;
}
}
if(stat.type == Statement.TYPE_DO) {
if(extractLoop((DoStatement)stat)) {
return 2;
}
}
return res?1:0;
}
private static boolean extractLoop(DoStatement stat) {
if(stat.getLooptype() != DoStatement.LOOP_DO) {
return false;
}
for(StatEdge edge: stat.getLabelEdges()) {
if(edge.getType() != StatEdge.TYPE_CONTINUE && edge.getDestination().type != Statement.TYPE_DUMMYEXIT) {
return false;
}
}
if(!extractLastIf(stat)) {
return extractFirstIf(stat);
} else {
return true;
}
}
private static boolean extractLastIf(DoStatement stat) {
// search for an if condition at the end of the loop
Statement last = stat.getFirst();
while(last.type == Statement.TYPE_SEQUENCE) {
last = last.getStats().getLast();
}
if(last.type == Statement.TYPE_IF) {
IfStatement lastif = (IfStatement)last;
if(lastif.iftype == IfStatement.IFTYPE_IF && lastif.getIfstat() != null) {
Statement ifstat = lastif.getIfstat();
StatEdge elseedge = lastif.getAllSuccessorEdges().get(0);
if(elseedge.getType() == StatEdge.TYPE_CONTINUE && elseedge.closure == stat) {
Set<Statement> set = stat.getNeighboursSet(StatEdge.TYPE_CONTINUE, Statement.DIRECTION_BACKWARD);
set.remove(last);
if(set.isEmpty()) { // no direct continues in a do{}while loop
if(isExternStatement(stat, ifstat, ifstat)) {
extractIfBlock(stat, lastif);
return true;
}
}
}
}
}
return false;
}
private static boolean extractFirstIf(DoStatement stat) {
// search for an if condition at the entrance of the loop
Statement first = stat.getFirst();
while(first.type == Statement.TYPE_SEQUENCE) {
first = first.getFirst();
}
// found an if statement
if(first.type == Statement.TYPE_IF) {
IfStatement firstif = (IfStatement)first;
if(firstif.getFirst().getExprents().isEmpty()) {
if(firstif.iftype == IfStatement.IFTYPE_IF && firstif.getIfstat()!=null) {
Statement ifstat = firstif.getIfstat();
if(isExternStatement(stat, ifstat, ifstat)) {
extractIfBlock(stat, firstif);
return true;
}
}
}
}
return false;
}
private static boolean isExternStatement(DoStatement loop, Statement block, Statement stat) {
for(StatEdge edge: stat.getAllSuccessorEdges()) {
if(loop.containsStatement(edge.getDestination()) &&
!block.containsStatement(edge.getDestination())) {
return false;
}
}
for(Statement st: stat.getStats()) {
if(!isExternStatement(loop, block, st)) {
return false;
}
}
return true;
}
private static void extractIfBlock(DoStatement loop, IfStatement ifstat) {
Statement target = ifstat.getIfstat();
StatEdge ifedge = ifstat.getIfEdge();
ifstat.setIfstat(null);
ifedge.getSource().changeEdgeType(Statement.DIRECTION_FORWARD, ifedge, StatEdge.TYPE_BREAK);
ifedge.closure = loop;
ifstat.getStats().removeWithKey(target.id);
loop.addLabeledEdge(ifedge);
SequenceStatement block = new SequenceStatement(Arrays.asList(new Statement[] {loop, target}));
loop.getParent().replaceStatement(loop, block);
block.setAllParent();
loop.addSuccessor(new StatEdge(StatEdge.TYPE_REGULAR, loop, target));
for(StatEdge edge: new ArrayList<StatEdge>(block.getLabelEdges())) {
if(edge.getType() == StatEdge.TYPE_CONTINUE || edge == ifedge) {
loop.addLabeledEdge(edge);
}
}
for(StatEdge edge: block.getPredecessorEdges(StatEdge.TYPE_CONTINUE)) {
if(loop.containsStatementStrict(edge.getSource())) {
block.removePredecessor(edge);
edge.getSource().changeEdgeNode(Statement.DIRECTION_FORWARD, edge, loop);
loop.addPredecessor(edge);
}
}
}
}
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