//******************************************************************
#region [CurrentBranchMatchesPattern() Method]
//******************************************************************
/// <summary>
/// Compares the trees dominated by the CurrentParseTreeNode and the
/// FindPatternRoot. If these trees match, true is returned and the
/// MatchingNodes stack contains the list of matching node pairs.
/// Otherwise, false is returned.
/// </summary>
public bool CurrentBranchMatchesPattern()
{
Debug.WriteLineIf(VerboseDebugging,
"MatchAlgorithm.CurrentBranchMatchesPattern() called.");
//**************************************************************
// Validate the current state.
if (FindPatternRoot == null)
{
string sMessage = "CurrentBranchMatchesPattern() "
+ "called with an invalid state: "
+ "FindPatternRoot is null.";
throw new Exception(sMessage);
}
if (CurrentParseTreeNode == null)
{
string sMessage = "CurrentBranchMatchesPattern() "
+ "called with an invalid state: "
+ "CurrentParseTreeNode is null.";
throw new Exception(sMessage);
}
//**************************************************************
// Clear the stack of matching node pairs.
MatchingNodes.Clear();
//**************************************************************
// Call FeaturesAndChildrenMatch() to check if the current
// parse-tree branch matches the find-pattern tree. If so,
// return true.
SyntaxNodePair oNodePair = new SyntaxNodePair();
oNodePair.ParseTreeNode = CurrentParseTreeNode;
oNodePair.FindPatternNode = FindPatternRoot;
if (FeaturesAndChildrenMatch(oNodePair))
{
Debug.Assert(MatchingNodes.Count > 0);
Debug.WriteLineIf(VerboseDebugging,
"MatchAlgorithm.CurrentBranchMatchesPattern() returns "
+ "true.");
return(true);
}
//**************************************************************
// The current parse-tree branch does not match the find-pattern
// tree, so return false.
//
// Note: The matching procedure should have cleared all node
// pairs from the MatchingNodes stack if the match failed.
Debug.Assert(MatchingNodes.Count == 0);
MatchingNodes.Clear();
Debug.WriteLineIf(VerboseDebugging,
"MatchAlgorithm.CurrentBranchMatchesPattern() returns "
+ "false.");
return(false);
}
//******************************************************************
#region [FindNextMatchingBranch() Method]
//******************************************************************
/// <summary>
/// Moves the CurrentParseTreeNode forward in the parse tree, until
/// the sub-tree dominated by this node matches the pattern
/// dominated by FindPatternRoot. If CurrentParseTreeNode is null
/// when this method is called, the search starts with the first
/// node in the parse tree. Otherwise, the search continues with the
/// next node in the tree. If a matching sub-tree is found, true is
/// returned and the MatchingNodes stack contains the list of
/// matching node pairs. If no match is found, CurrentParseTreeNode
/// is set to null and false is returned.
/// </summary>
public bool FindNextMatchingBranch()
{
Debug.WriteLineIf(VerboseDebugging,
"FindAlgorithm.FindNextMatchingBranch() called.");
//**************************************************************
// Validate the current state.
if (CurrentParseTreeNode != null)
{
SyntaxNode oNode = CurrentParseTreeNode;
while (oNode != ParseTreeRoot)
{
if (oNode.ParentNode == null)
{
string sMessage = "FindNextMatchingBranch() "
+ "called with an invalid state: "
+ "the ParseTreeRoot tree does not contain "
+ "the CurrentParseTreeNode.";
throw new Exception(sMessage);
}
oNode = oNode.ParentNode;
}
}
//**************************************************************
// Clear the lists of MatchingNodes and ReplacedNodes.
MatchingNodes.Clear();
ReplacedNodes.Clear();
//**************************************************************
// Save the previous value of the CurrentParseTreeNode.
SyntaxNode oPreviousParseTreeNode = CurrentParseTreeNode;
//**************************************************************
// Move the CurrentParseTreeNode to the next branch to compare:
//
// If CurrentParseTreeNode is null, start with the first
// parse-tree node in post order.
//
// Otherwise, move to the next node in post order.
//
// Note: The parse tree is traversed in post-order (parent after
// its children) to prevent infinite recursion that could occur
// if an XP node was replaced by a node with XP children, and
// then the rule was applied recursively to these children.
if (CurrentParseTreeNode == null)
{
CurrentParseTreeNode
= GetFirstNodeInPostOrder(ParseTreeRoot);
}
else
{
CurrentParseTreeNode
= GetNextNodeInPostOrder(CurrentParseTreeNode);
}
//**************************************************************
// Check if the previous branch should be deleted.
//
// When the ReplaceCurrentMatchingBranch() method needs to
// delete the current parse-tree node, it sets it to an empty
// node (one with no features and no children) instead. This is
// so we can use the current parse-tree node to determine where
// to find the next node to compare.
//
// If the previous branch is an empty node (with no features and
// no children), delete it.
if (oPreviousParseTreeNode != null)
{
if ((oPreviousParseTreeNode.Features.Count == 0) &&
(oPreviousParseTreeNode.ChildNodes.Count == 0))
{
//******************************************************
// Remove the empty node from its parent's ChildNodes
// collection. If the empty node is the same as the
// ParseTreeRoot, set the ParseTreeRoot to null.
SyntaxNode oParent = oPreviousParseTreeNode.ParentNode;
if (oParent != null)
{
oParent.ChildNodes.Remove(oPreviousParseTreeNode);
}
if (oPreviousParseTreeNode == ParseTreeRoot)
{
ParseTreeRoot = null;
}
}
}
//**************************************************************
// If FindPatternRoot is null, nothing can match this pattern.
// In this case, set CurrentParseTreeNode to null so there will
// be no comparisons and false will be returned.
if (FindPatternRoot == null)
{
CurrentParseTreeNode = null;
}
//**************************************************************
// Traverse the parse tree (in post order), looking for a match,
// until there are no more nodes to traverse. Return true if a
// match is found.
while (CurrentParseTreeNode != null)
{
//**********************************************************
// Return true if the current branch matches the pattern.
if (CurrentBranchMatchesPattern())
{
Debug.Assert(MatchingNodes.Count > 0);
Debug.Assert(ReplacedNodes.Count == 0);
Debug.Assert(CurrentParseTreeNode != null);
Debug.WriteLineIf(VerboseDebugging,
"FindAlgorithm.FindNextMatchingBranch() returns "
+ "true.");
return(true);
}
//**********************************************************
// Move to the next node in post order.
CurrentParseTreeNode
= GetNextNodeInPostOrder(CurrentParseTreeNode);
}
//**************************************************************
// A matching branch was not found, so return false.
Debug.Assert(MatchingNodes.Count == 0);
Debug.Assert(ReplacedNodes.Count == 0);
Debug.Assert(CurrentParseTreeNode == null);
Debug.WriteLineIf(VerboseDebugging,
"FindAlgorithm.FindNextMatchingBranch() returns false.");
return(false);
}