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package org.eclipse.cdt.internal.core.parser;
import java.util.EmptyStackException;
import java.util.Stack;
/**
* @author jcamelon
*
* To change this generated comment edit the template variable
"typecomment":
* Window>Preferences>Java>Templates.
* To enable and disable the creation of type comments go to
* Window>Preferences>Java>Code Generation.
*/
public class BranchTracker {
private static final int IGNORE_SENTINEL = -1;
/**
* Default constructor.
*
* @see java.lang.Object#Object()
*/
public BranchTracker()
{
}
private Stack branches = new Stack();
private int ignore = IGNORE_SENTINEL;
private static final Boolean FALSE = new Boolean( false );
private static final Boolean TRUE = new Boolean( true );
/**
* Method poundif.
*
* This method is called whenever one encounters a #if, #ifndef
* or #ifdef preprocessor directive.
*
* @param taken - boolean indicates whether or not the condition
* evaluates to true or false
* @return boolean - are we set to continue scanning or not?
*/
public boolean poundif( boolean taken )
{
if( ignore == IGNORE_SENTINEL )
{
// we are entering an if
// push the taken value onto the stack
branches.push( new Boolean( taken ) );
if( taken == false )
{
ignore = branches.size();
}
return taken;
}
else
{
branches.push( FALSE );
return false;
}
}
public boolean poundelif( boolean taken ) throws EmptyStackException
{
if( ignore != IGNORE_SENTINEL && ignore < branches.size() )
{
branches.pop();
branches.push( FALSE );
return false;
}
// so at this point we are either
// --> ignore == IGNORE_SENTINEL
// --> ignore >= branches.size()
// check the branch queue to see whether or not the branch has already been taken
Boolean branchAlreadyTaken;
branchAlreadyTaken = (Boolean) branches.peek();
if( ignore == IGNORE_SENTINEL )
{
if( ! branchAlreadyTaken.booleanValue() )
{
branches.pop();
branches.push( new Boolean( taken ) );
if( ! taken )
ignore = branches.size();
return taken;
}
// otherwise this section is to be ignored as well
ignore = branches.size();
return false;
}
// if we have gotten this far then ignore == branches.size()
if( ! branchAlreadyTaken.booleanValue() )
{
branches.pop();
branches.push( new Boolean( taken ) );
if( taken )
ignore = IGNORE_SENTINEL;
return taken;
}
ignore = branches.size();
return false;
}
public boolean poundelse() throws EmptyStackException
{
if( ignore != IGNORE_SENTINEL && ignore < branches.size() )
{
branches.pop();
branches.push( FALSE );
return false;
}
Boolean branchAlreadyTaken;
branchAlreadyTaken = (Boolean) branches.peek();
if( ignore == IGNORE_SENTINEL )
{
if( branchAlreadyTaken.booleanValue() )
{
ignore = branches.size();
return false;
}
branches.pop();
branches.push( TRUE );
return true;
}
// now ignore >= branches.size()
if( branchAlreadyTaken.booleanValue() )
{
ignore = branches.size();
return false;
}
branches.pop();
branches.push( TRUE );
ignore = IGNORE_SENTINEL;
return true;
}
// taken only on an #endif
public boolean poundendif( )
{
if( ignore == branches.size() )
ignore = IGNORE_SENTINEL;
branches.pop();
return ( ignore == IGNORE_SENTINEL );
}
public int getDepth()
{
return branches.size();
}
}
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