jode/jode/src/net/sf/jode/flow/CatchBlock.java

/* CatchBlock Copyright (C) 1998-2002 Jochen Hoenicke.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; see the file COPYING.LESSER.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id$
 */

package net.sf.jode.flow;
import net.sf.jode.type.Type;
import net.sf.jode.decompiler.LocalInfo;
import net.sf.jode.decompiler.Declarable;
import net.sf.jode.expr.Expression;
import net.sf.jode.expr.LocalLoadOperator;
import net.sf.jode.expr.LocalStoreOperator;
import net.sf.jode.expr.NopOperator;
import net.sf.jode.expr.Operator;
import net.sf.jode.expr.StoreInstruction;

///#def COLLECTIONS java.util
import java.util.Collections;
import java.util.Iterator;
import java.util.Set;
///#enddef


/**
 * 
 * @author Jochen Hoenicke
 */
public class CatchBlock extends StructuredBlock {
    
    /**
     * The catch block.
     */
    StructuredBlock catchBlock;

    /**
     * The type of the exception.
     */
    Type exceptionType;
    
    /**
     * The local containing the exception. May be null.
     */
    LocalInfo exceptionLocal;

    public CatchBlock(Type type) {
        exceptionType = type;
    }

    public Type getExceptionType() {
	return exceptionType;
    }

    public LocalInfo getLocal() {
	return exceptionLocal;
    }

    /** 
     * Sets the catch block.
     * @param catchBlock the catch block.
     */
    public void setCatchBlock(StructuredBlock catchBlock) {
        this.catchBlock = catchBlock;
        catchBlock.outer = this;
        catchBlock.setFlowBlock(flowBlock);
	if (exceptionLocal == null)
	    combineLocal();
    }

    /* The implementation of getNext[Flow]Block is the standard
     * implementation */

    /**
     * Replaces the given sub block with a new block.
     * @param oldBlock the old sub block.
     * @param newBlock the new sub block.
     * @return false, if oldBlock wasn't a direct sub block.
     */
    public boolean replaceSubBlock(StructuredBlock oldBlock, 
                                   StructuredBlock newBlock) {
        if (catchBlock == oldBlock)
            catchBlock = newBlock;
        else
            return false;
        return true;
    }

    /**
     * Returns all sub block of this structured block.
     */
    public StructuredBlock[] getSubBlocks() {        
        return new StructuredBlock[] { catchBlock };
    }

    LocalInfo pushedLocal;

    /**
     * A catch block pushes the exception on the stack, iff a local
     * doesn't exists.
     * @param stack the stack before the instruction is called
     * @return stack the stack afterwards.
     */
    public VariableStack mapStackToLocal(VariableStack stack) {
	VariableStack newStack;
	if (exceptionLocal == null) {
	    pushedLocal = new LocalInfo();
	    pushedLocal.setType(exceptionType);
	    newStack = stack.push(pushedLocal);
	} else
	    newStack = stack;
	return super.mapStackToLocal(newStack);
    }

    public void removePush() {
	if (pushedLocal != null)
	    exceptionLocal = pushedLocal;
	super.removePush();
    }

    public Set getDeclarables() {
	if (exceptionLocal != null)
	    return Collections.singleton(exceptionLocal);
	return Collections.EMPTY_SET;
    }
    
    /**
     * Make the declarations, i.e. initialize the declare variable
     * to correct values.  This will declare every variable that
     * is marked as used, but not done.
     * @param done The set of the already declare variables.
     */
    public void makeDeclaration(Set done) {
	super.makeDeclaration(done);
	/* Normally we have to declare our exceptionLocal.  This
	 * is automatically done in dumpSource.
	 *
	 * If we are unlucky the exceptionLocal is used outside of 
	 * this block.  In that case we do a transformation.
	 */
	if (exceptionLocal != null) {
	    if (declare.contains(exceptionLocal))
		declare.remove(exceptionLocal);
	    else {
		LocalInfo dummyLocal = new LocalInfo();
		Expression store = new StoreInstruction
		    (new LocalStoreOperator
		     (exceptionLocal.getType(), exceptionLocal)).addOperand
		    (new LocalLoadOperator(dummyLocal.getType(), 
					   null, dummyLocal));
		InstructionBlock ib = new InstructionBlock(store);
		ib.setFlowBlock(flowBlock);
		ib.appendBlock(catchBlock);
		catchBlock = ib;
		exceptionLocal = dummyLocal;
		String localName = dummyLocal.guessName();
		Iterator doneIter = done.iterator();
		while (doneIter.hasNext()) {
		    Declarable previous = (Declarable) doneIter.next();
		    if (localName.equals(previous.getName())) {
			/* A name conflict happened. */
			dummyLocal.makeNameUnique();
			break;
		    }
		}
	    }
	}
    }

    public void dumpInstruction(net.sf.jode.decompiler.TabbedPrintWriter writer) 
        throws java.io.IOException {
	writer.closeBraceContinue();
        writer.print("catch (");
	writer.printType(exceptionType);
	writer.print(" " + (exceptionLocal != null
			    ? exceptionLocal.getName() : "PUSH") + ")");
	writer.openBrace();
        writer.tab();
        catchBlock.dumpSource(writer);
        writer.untab();
    }

    /**
     * Determines if there is a sub block, that flows through to the end
     * of this block.  If this returns true, you know that jump is null.
     * @return true, if the jump may be safely changed.
     */
    public boolean jumpMayBeChanged() {
        return (catchBlock.jump != null || catchBlock.jumpMayBeChanged());
    }

    /**
     * Check if this is an local store instruction to a not yet declared
     * variable.  In that case mark this as declaration and return the 
     * variable.
     */
    public boolean combineLocal() {
	StructuredBlock firstInstr = (catchBlock instanceof SequentialBlock)
            ? catchBlock.getSubBlocks()[0] : catchBlock;

	if (firstInstr instanceof SpecialBlock
	    && ((SpecialBlock) firstInstr).type == SpecialBlock.POP
	    && ((SpecialBlock) firstInstr).count == 1) {
	    /* The exception is ignored.  Create a dummy local for it */
	    exceptionLocal = new LocalInfo();
	    exceptionLocal.setType(exceptionType);
	    firstInstr.removeBlock();
	    return true;
	} else if (firstInstr instanceof InstructionBlock) {
            Expression instr = 
                ((InstructionBlock) firstInstr).getInstruction();
            if (instr instanceof StoreInstruction) {
		StoreInstruction store = (StoreInstruction) instr;
		if (store.getOperatorIndex() == Operator.OPASSIGN_OP
		    && store.getSubExpressions()[1] instanceof NopOperator
		    && store.getLValue() instanceof LocalStoreOperator) {
		    /* The exception is stored in a local variable */
		    exceptionLocal = ((LocalStoreOperator) store.getLValue())
			.getLocalInfo();
		    exceptionLocal.setType(exceptionType);
		    firstInstr.removeBlock();
		    return true;
		}
	    }
        }
	return false;
    }
}