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

/* CaseBlock 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.expr.ConstOperator;
import net.sf.jode.type.Type;

/** 
 * This block represents a case instruction.  A case instruction is a
 * part of a switch construction and may have a subpart or not (for
 * multiple case directly after each other.
 *
 * @author Jochen Hoenicke */
public class CaseBlock extends StructuredBlock {
    /**
     * The inner block that jumps to the subroutine, or null
     * if this is a value only.
     */
    StructuredBlock subBlock;

    /**
     * The value of this case.
     */
    int value;

    /**
     * True, if this is the default case
     */
    boolean isDefault = false;

    /**
     * True, if the previous case falls through to this case
     */
    boolean isFallThrough = false;

    /**
     * True, if this is the last case in a switch
     */
    boolean isLastBlock = false;

    public CaseBlock(int value) {
	this(false);
	this.value = value;
    }

    public CaseBlock(boolean isDef) {
	isDefault = isDef;
	subBlock = new EmptyBlock();
	subBlock.outer = this;
    }

    public void checkConsistent() {
        if (!(outer instanceof SwitchBlock))
            throw new InternalError("Inconsistency");
        super.checkConsistent();
    }

    /**
     * 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 (subBlock == oldBlock)
            subBlock = newBlock;
        else
            return false;
        return true;
    }

    /**
     * Tells if we want braces around this case.  We only need braces
     * if there is a declaration on the first level (list of
     * sequential blocks).
     */
    protected boolean wantBraces() {
	StructuredBlock block = subBlock;
	if (block instanceof EmptyBlock)
	    return false;
	for (;;) {
	    if (block.declare != null && !block.declare.isEmpty()) {
		/* A declaration; we need braces. */
		return true;
	    }

	    if (!(block instanceof SequentialBlock)) {
		/* This was the last block on the first level. 
		 * Finally check if that is an declaring InstructionBlock.
		 */
		if (block instanceof InstructionBlock 
		    && ((InstructionBlock)block).isDeclaration)
		    return true;


		/* If we get here, we need no braces.
		 */
		return false;
	    }
	    
	    StructuredBlock[] subBlocks = block.getSubBlocks();
	    if (subBlocks[0] instanceof InstructionBlock
		&& ((InstructionBlock)subBlocks[0]).isDeclaration) {
		/* An instruction block declares on the same level as
		 * the surrounding SequentialBlock.
		 */
		return true;
	    }

	    /* continue with the second sub block. */
	    block = subBlocks[1];
	}
    }

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

    public void dumpInstruction(net.sf.jode.decompiler.TabbedPrintWriter writer) 
        throws java.io.IOException 
    {
	if (isDefault) {
	    /* If this is the default case and does nothing, we can
	     * skip this.  
	     * We have to make sure, that nothing flows into the default
	     * block though. XXX remove if sure.
	     */
	    if (isLastBlock
		&& subBlock instanceof EmptyBlock
		&& subBlock.jump == null)
		return;
	    if (subBlock instanceof BreakBlock
		&& ((BreakBlock) subBlock).breaksBlock == this) {
		/* make sure that the previous block is correctly breaked */
		if (isFallThrough) {
		    writer.tab();
		    subBlock.dumpSource(writer);
		    writer.untab();
		}
		return;
	    }
	    if (isFallThrough) {
		writer.tab();
		writer.println("/* fall through */");
		writer.untab();
	    }
	    writer.print("default:");
	} else {
	    if (isFallThrough) {
		writer.tab();
		writer.println("/* fall through */");
		writer.untab();
	    }
            ConstOperator constOp = new ConstOperator(new Integer(value));
	    Type type = ((SwitchBlock)outer).getInstruction().getType();
	    constOp.setType(type);
            constOp.makeInitializer(type);
	    writer.print("case " + constOp.toString() + ":");
        }
	if (subBlock instanceof EmptyBlock
	    && subBlock.jump == null) {
	    writer.println();
	} else {
	    boolean needBraces = wantBraces();
	    if (needBraces)
		writer.openBrace();
	    else
		writer.println();
	    if (subBlock != null) {
		writer.tab();
		subBlock.dumpSource(writer);
		writer.untab();
	    }
	    if (needBraces)
		writer.closeBrace();
	}
    }

    /**
     * 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 subBlock.jump != null || subBlock.jumpMayBeChanged();
    }
}