public void Clear(bool all = true)
{
if (all)
{
ProdStartLoc = 0;
Prod = null;
TermIndex = 0;
AstProd = null;
}
OptionalState = OptionalTermState.Start;
OptionalStartLoc = 0;
OrState = OrTermState.Start;
OrProdIndex = 0;
OrStartLoc = 0;
ProdMatched = false;
ListState = ListTermState.Start;
ListCount = 0;
ListSeparatorStartLoc = 0;
SubResult.ErrorMessage = "Uninitialized result";
SubResult.IsMatch = false;
}
public static MatchResult Match(string rootProdName, TokenQueue q, out Ast.SqliteSyntaxProduction ast)
{
// we use an explicit stack rather than function call recursion because our BNF grammar is deeply nested,
// particularly the productions for 'expr'.
var stack = new MatchStack {
Queue = q
};
stack.Push(SqliteGrammar.Prods[rootProdName]);
MatchResult?rootResult = null;
Ast.SqliteSyntaxProduction rootAst = null;
Action <MatchResult, Ast.SqliteSyntaxProduction> finishFrame = (frameResult, frameAstProd) => {
stack.Pop();
var parentFrame = stack.Peek();
if (parentFrame == null)
{
rootResult = frameResult;
rootAst = frameAstProd;
}
else
{
parentFrame.SubResult = frameResult;
if (frameResult.IsMatch)
{
parentFrame.AstProd.Items.Add(frameAstProd);
}
}
};
#if MATCHER_LOG
var matcherLogWriter = File.CreateText(@"C:\temp\matcher.log");
int matcherLogPreviousDepth = 0;
#endif
// trampoline loop
while (!rootResult.HasValue && stack.Any())
{
#if MATCHER_LOG
stack.DebugDump(matcherLogWriter, q.GetLocation(), q.Substring(q.GetLocation(), 1),
matcherLogPreviousDepth > stack.Count);
matcherLogPreviousDepth = stack.Count;
#endif
var frame = stack.Peek();
var result = frame.Prod.Terms[frame.TermIndex].MatchStep(stack, frame, q);
if (result.HasValue)
{
// we are done matching this term
if (result.Value.IsMatch)
{
// move to the next term in the production.
frame.Clear(all: false);
frame.TermIndex++;
if (frame.TermIndex >= frame.Prod.Terms.Length)
{
// we have matched this full production
var prodEndLoc = q.GetLocation();
frame.AstProd.StartToken = frame.ProdStartLoc;
frame.AstProd.NumTokens = prodEndLoc - frame.ProdStartLoc;
frame.AstProd.Text = q.Substring(frame.ProdStartLoc, prodEndLoc - frame.ProdStartLoc);
finishFrame(MatchResult.Matched, frame.AstProd);
}
}
else
{
// we needed a match and didn't find one. we have to abandon this production.
finishFrame(result.Value, null);
}
}
}
#if MATCHER_LOG
matcherLogWriter.Close();
#endif
if (!rootResult.HasValue && !stack.Any()) // detect bugs
{
throw new Exception("Expected a MatchResult but one was not set.");
}
ast = rootAst;
return(rootResult.Value);
}