/// <summary>
/// Based on: http://www.goldparser.org/doc/engine-pseudo/parse-token.htm
/// </summary>
/// <param name="tokenIterator">Token iterator which will be owned by the caller</param>
/// <param name="debugger">Enables debugging support</param>
/// <param name="trimReductions">If true (default), trim reductions of the form L -> R, where R is a non-terminal</param>
/// <param name="allowRewriting">Apply rewriting functions</param>
/// <returns>The reduced program tree on acceptance or the erroneous token</returns>
public async Task<Token> ParseInputAsync(IAsyncLAIterator<Token> tokenIterator, Debug debugger,
bool trimReductions = true,
bool allowRewriting = true)
{
const int initState = 0;
var tokenStack = new Stack<Token>();
var state = initState;
while (true)
{
var token = await tokenIterator.LookAheadAsync();
var action = ParseTable.Actions[state, token.ID + 1];
debugger.DumpParsingState(state, tokenStack, token, action);
switch (action.ActionType)
{
case ActionType.Shift:
state = action.ActionParameter;
token.State = state;
tokenStack.Push(token);
await tokenIterator.MoveNextAsync();
break;
case ActionType.Reduce:
var nProduction = action.ActionParameter;
var production = Productions[nProduction];
var nChildren = production.Right.Length;
Token reduction;
if (trimReductions && nChildren == 1 && _nonterminals.Contains(production.Right[0]))
{
reduction = new Token(production.Left, tokenStack.Pop().Content);
}
else
{
var children = new Token[nChildren];
for (var i = 0; i < nChildren; i++)
{
children[nChildren - i - 1] = tokenStack.Pop();
}
var rewrite = (allowRewriting ? production.Rewrite(children) : null) ??
new Reduction(nProduction, children);
reduction = new Token(production.Left, rewrite);
}
var lastState = tokenStack.Count > 0 ? tokenStack.Peek().State : initState;
state = ParseTable.Actions[lastState, production.Left + 1].ActionParameter;
reduction.State = production.Left;
tokenStack.Push(reduction);
if (tokenStack.Count == 1 && tokenStack.Peek().ID == 0)
{
return tokenStack.Pop();
}
break;
case ActionType.Error:
return token;
case ActionType.ErrorRR:
throw new InvalidOperationException("Reduce-Reduce conflict in grammar: " + token);
case ActionType.ErrorSR:
throw new InvalidOperationException("Shift-Reduce conflict in grammar: " + token);
}
debugger.Flush();
}
}
/// <summary>
/// Based on: http://www.goldparser.org/doc/engine-pseudo/parse-Item.htm
/// </summary>
/// <param name="tokenIterator">Item iterator which will be owned by the caller</param>
/// <param name="debugger">Enables debugging support</param>
/// <param name="trimReductions">If true (default), trim reductions of the form L -> R, where R is a non-terminal</param>
/// <param name="allowRewriting">Apply rewriting functions</param>
/// <returns>The reduced program tree on acceptance or the erroneous Item</returns>
public async Task <Item> ParseInputAsync(IAsyncLAIterator <Item> tokenIterator, Debug debugger,
bool trimReductions = true,
bool allowRewriting = true)
{
const int initState = 0;
var tokenStack = new Stack <Item>();
var state = initState;
while (true)
{
var token = await tokenIterator.LookAheadAsync();
var action = ParseTable.Actions[state, token.ID + 1];
debugger.DumpParsingState(state, tokenStack, token, action);
switch (action.ActionType)
{
case ActionType.Shift:
state = action.ActionParameter;
token.State = state;
tokenStack.Push(token);
await tokenIterator.MoveNextAsync();
break;
case ActionType.Reduce:
var nProduction = action.ActionParameter;
var production = Productions[nProduction];
var nChildren = production.Right.Length;
Item reduction;
if (trimReductions && nChildren == 1 && _nonterminals.Contains(production.Right[0]))
{
reduction = new Item(production.Left, tokenStack.Pop().Content);
}
else
{
var children = new Item[nChildren];
for (var i = 0; i < nChildren; i++)
{
children[nChildren - i - 1] = tokenStack.Pop();
}
var rewrite = (allowRewriting ? production.Rewrite(children) : null) ??
new Reduction(nProduction, children);
reduction = new Item(production.Left, rewrite);
}
var lastState = tokenStack.Count > 0 ? tokenStack.Peek().State : initState;
state = ParseTable.Actions[lastState, production.Left + 1].ActionParameter;
reduction.State = production.Left;
tokenStack.Push(reduction);
if (tokenStack.Count == 1 && tokenStack.Peek().ID == 0)
{
return(tokenStack.Pop());
}
break;
case ActionType.Error:
token.State = state < 0 ? state : -state;
return(token);
case ActionType.ErrorRR:
throw new InvalidOperationException("Reduce-Reduce conflict in grammar: " + token);
case ActionType.ErrorSR:
throw new InvalidOperationException("Shift-Reduce conflict in grammar: " + token);
}
debugger.Flush();
}
}
public async Task <bool> MoveNextAsync()
{
var buffer = new StringBuilder(4);
var statePatterns = _patternTable[_states.Peek()];
var matchingPatterns = new List <RegexTuple>(statePatterns);
do
{
if (!await _charSource.MoveNextAsync())
{
return(false);
}
var textWithLA = await FillBufferAsync(buffer);
for (var i = 0; i < matchingPatterns.Count; i++)
{
var pattern = matchingPatterns[i];
var match = pattern.Item2.Match(textWithLA);
if (!match.Success || match.Length == 0)
{
matchingPatterns.RemoveAt(i--);
}
}
} while (matchingPatterns.Count > 1);
if (matchingPatterns.Count == 0)
{
return(false);
}
var matchingPattern = matchingPatterns[0];
do
{
var lookAhead = await FillLookAheadAsync(buffer, true);
if (lookAhead == null)
{
break;
}
var textWithLA = buffer.ToString();
var match = matchingPattern.Item2.Match(textWithLA);
if (!match.Success || match.Length < textWithLA.Length)
{
RemoveLookAhead(buffer, lookAhead);
break;
}
if (!await _charSource.MoveNextAsync())
{
break;
}
} while (true);
_currentItem = new Item(matchingPattern.Item1, buffer.ToString());
var instructionList = matchingPattern.Item3;
if (!string.IsNullOrEmpty(instructionList))
{
foreach (var instruction in instructionList.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
{
switch (instruction)
{
case PopState:
_states.Pop();
break;
case Ignore:
return(await MoveNextAsync());
default:
_states.Push(matchingPattern.Item3);
break;
}
}
}
return(true);
}
