private T Parse(ILexerInstance <T> lexerInstance)
{
var valueStack = new Stack <T>();
var parseStack = new Stack <int>();
// Push default state onto the parse stack. Default state is always 0
parseStack.Push(0);
var input = lexerInstance.Next();
// This holds the last exception we found when parsing, since we
// will need to pass this to an error handler once the proper handler has been found
ParseException exception = null;
while (true)
{
int state = parseStack.Peek();
int action = parseTable.Action[state, input.Item1];
if (action >= 0)
{
if (action == short.MaxValue)
{
// Accept!
return(valueStack.Pop());
}
// Shift
parseStack.Push(input.Item1); // Push token unto stack
parseStack.Push(action); // Push state unto stack
// Shift token value unto value stack
valueStack.Push(input.Item2);
// Lex next token
input = lexerInstance.Next();
}
else
{
if (action == short.MinValue)
{
// Get the expected tokens
string[] expectedTokens = GetExpectedTokenNames(state).ToArray();
// Create an exception that either might be thrown or may be handed to the error handling routine.
exception = new ParseException(string.Format("Illegal token {0}. Expected {1}",
terminalDebugNames[input.Item1], string.Join(",", expectedTokens)))
{
LexerState = lexerInstance,
FoundToken = terminalDebugNames[input.Item1],
ExpectedTokens = expectedTokens,
FoundTokenId = input.Item1,
ParserState = state
};
// Go for error recovery!
while (parseTable.Action[parseStack.Peek(), errorTokenNumber] == short.MinValue)
{
// If we run out of stack while searching for the error handler, throw the exception
// This is what happens when there is no error handler defined at all.
if (parseStack.Count <= 2)
{
throw exception;
}
parseStack.Pop(); // Pop state
parseStack.Pop(); // Pop token
valueStack.Pop(); // Pop whatever value
}
// Shift the error token unto the stack
state = parseStack.Peek();
parseStack.Push(errorTokenNumber);
parseStack.Push(parseTable.Action[state, errorTokenNumber]);
valueStack.Push(default(T));
state = parseStack.Peek();
// We have now found a state where error recovery is enabled. This means that we
// continue to scan the input stream looking for something which is accepted.
// End of input will cause the exception to be thrown
for (; parseTable.Action[state, input.Item1] == short.MinValue &&
input.Item1 != endOfInputTokenNumber; input = lexerInstance.Next())
{
; // nom nom nom
}
// Ran out of file looking for the end of the error rule
if (input.Item1 == endOfInputTokenNumber)
{
throw exception;
}
// If we get here we are pretty cool, continue running the parser. The actual error recovery routine will be
// called as soon as the error rule itself is reduced.
}
else
{
// Get the right reduction rule to apply
var reductionRule = parseTable.ReductionRules[-(action + 1)];
for (int i = 0; i < reductionRule.NumTokensToPop * 2; ++i)
{
parseStack.Pop();
}
// Transfer to state found in goto table
int stateOnTopOfStack = parseStack.Peek();
parseStack.Push(reductionRule.TokenToPush);
parseStack.Push(parseTable.Goto[stateOnTopOfStack, reductionRule.TokenToPush]);
// Get tokens off the value stack for the OnReduce function to run on
var onReduceParams = new T[reductionRule.NumTokensToPop];
// Need to do it in reverse since thats how the stack is organized
for (int i = reductionRule.NumTokensToPop - 1; i >= 0; --i)
{
onReduceParams[i] = valueStack.Pop();
}
// This calls the reduction function with the possible exception set. The exception could be cleared here, but
// there is no real reason to do so, since all the normal rules will ignore it, and all the error rules are guaranteed
// to have the exception set prior to entering the reduction function.
var reduceFunc = reductionRule.OnReduce;
valueStack.Push(reduceFunc == null ? default(T) : reduceFunc(exception, onReduceParams));
}
}
}
}
private T Parse(ILexerInstance <T> lexerInstance)
{
Stack <T> valueStack = new Stack <T>();
Stack <int> parseStack = new Stack <int>();
// This holds the last exception we found when parsing, since we will need to pass this to an error handler once the proper handler has been found
ParseException exception = null;
// Push default state onto the parse stack. Default state is always 0
parseStack.Push(0);
Tuple <int, T> input = lexerInstance.Next();
while (true)
{
int state = parseStack.Peek();
int action = ParseTable.Action[state, input.Item1];
if (action >= 0)
{
if (action == short.MaxValue)
{
return(valueStack.Pop()); // Accept!
}
// Shift
parseStack.Push(input.Item1); // Push token unto stack
parseStack.Push(action); // Push state unto stack
// Shift token value unto value stack
valueStack.Push(input.Item2);
// Lex next token
input = lexerInstance.Next();
}
else if (action == short.MinValue)
{
// Get the expected tokens
string[] expectedTokens = GetExpectedTokenNames(state).ToArray();
// Create an exception that either might be thrown or may be handed to the error handling routine.
exception = new ParseException($"Illegal token '{terminalDebugNames[input.Item1]}', Expected '{string.Join(",", expectedTokens)}'.")
{
LexerState = lexerInstance,
FoundToken = terminalDebugNames[input.Item1],
ExpectedTokens = expectedTokens,
FoundTokenId = input.Item1,
ParserState = state
};
// Go for error recovery!
while (ParseTable.Action[parseStack.Peek(), errorTokenNumber] == short.MinValue)
{
if (parseStack.Count <= 2)
{
throw exception; // If we run out of stack while searching for the error handler, throw the exception. This is what happens when there is no error handler defined at all.
}
else
{
parseStack.Pop(); // Pop state
parseStack.Pop(); // Pop token
valueStack.Pop(); // Pop whatever value
}
}
// Shift the error token unto the stack
state = parseStack.Peek();
parseStack.Push(errorTokenNumber);
parseStack.Push(ParseTable.Action[state, errorTokenNumber]);
valueStack.Push(default);
