private bool DoReduction(Stack <Token> tokenStack, LookAheadBuffer lookAheadBuffer, ref ushort lalrState, LRAction parseAction)
{
Token head = null;
//Produce a reduction - remove as many tokens as members in the rule & push a nonterminal token
Production prod = egtDataManager.GetProduction(parseAction.Value);
bool reductionSkipped = false;
//Skip reduction?
if ((TrimReductions && prod.ConsistsOfOneNonTerminal()) ||
(SkipEmptyProductions && prod.Handle.Count == 0))
{
head = tokenStack.Pop();
head.Symbol = prod.Head;
reductionSkipped = true;
}
//Build a Reduction
else
{
Reduction reduction = new Reduction(prod.Handle.Count, prod);
//If a production has no handles, it has no location.
//Set a would-be location instead.
if (prod.Handle.Count == 0)
{
reduction.StartPosition = reduction.EndPosition = lookAheadBuffer.Position;
}
else
{
for (int i = prod.Handle.Count - 1; i >= 0; i--)
{
reduction[i] = tokenStack.Pop();
}
}
head = reduction;
}
//If n is -1 here, then we have an Internal Table Error!!!
LRAction action = egtDataManager.GetLRActionList(tokenStack.Peek().State)[prod.Head];
if (action == null)
{
OnInternalError();
return(false);
}
lalrState = action.Value;
head.State = lalrState;
tokenStack.Push(head);
if (!reductionSkipped)
{
OnReduction((Reduction)tokenStack.Peek());
}
return(true);
}
public bool Parse(TextReader reader)
{
if (egtDataManager == null)
{
OnNotLoadedError();
return false;
}
TokenQueueStack inputTokens = new TokenQueueStack();
Stack<Token> tokenStack = new Stack<Token>();
tokenStack.Push(new Token());
Stack<Token> groupStack = new Stack<Token>();
LookAheadBuffer lookAheadBuffer = new LookAheadBuffer(reader);
ushort lalrState = 0;
while (true)
{
if (inputTokens.Count == 0)
{
inputTokens.Push(ProduceToken(groupStack, lookAheadBuffer));
OnTokenRead(inputTokens.Peek());
}
//Runaway group
else if (groupStack.Count != 0)
{
OnGroupError();
return false; //Error; abort
}
else
{
Token read = inputTokens.Peek();
switch (read.Type)
{
case SymbolType.Noise:
inputTokens.Pop();
break;
case SymbolType.Error:
OnLexicalError(read.EndPosition, read.Data);
return false; //Error; abort
default:
LRActionList actionList = egtDataManager.GetLRActionList(lalrState);
LRAction parseAction = actionList[read.Symbol];
if (parseAction == null)
{
HandleSyntaxError(actionList, read);
return false;
}
switch (parseAction.Type)
{
case LRActionType.Accept:
OnCompleted(tokenStack.Peek().Tag);
return true;
case LRActionType.Shift:
lalrState = parseAction.Value;
read.State = lalrState;
tokenStack.Push(read);
//It now exists on the Token-Stack and must be eliminated from the queue.
inputTokens.Dequeue();
break;
case LRActionType.Reduce:
if (!DoReduction(tokenStack, lookAheadBuffer, ref lalrState, parseAction))
{
return false;
}
break;
}
break;
}
}
}
}
private Token ProduceToken(Stack<Token> groupStack, LookAheadBuffer lookAheadBuffer)
{
while (true)
{
Token read = LookAheadDFA(lookAheadBuffer);
if (read.Type == SymbolType.GroupStart && (groupStack.Count == 0 || groupStack.Peek().Group.Nesting.Contains(read.Group.TableIndex)))
{
lookAheadBuffer.Consume(read.Data.Length);
read.EndPosition = lookAheadBuffer.Position;
groupStack.Push(read);
}
else if (groupStack.Count == 0)
{
//The token is ready to be analyzed.
lookAheadBuffer.Consume(read.Data.Length);
read.EndPosition = lookAheadBuffer.Position;
return read;
}
else if (Object.ReferenceEquals(groupStack.Peek().Group.End, read.Symbol))
{
//End the current group
Token pop = groupStack.Pop();
if (pop.Group.Ending == GroupEndingMode.Closed)
{
pop.Data += read.Data;
lookAheadBuffer.Consume(read.Data.Length);
read.EndPosition = lookAheadBuffer.Position;
}
//We are out of the group. Return pop'd token (which contains all the group text)
if (groupStack.Count == 0)
{
//Change symbol to parent
pop.Symbol = pop.Group.Container;
return pop;
}
else
{
groupStack.Peek().Data += pop.Data;
}
}
else if (read.Type == SymbolType.End)
{
return read;
}
else
{
//We are in a group, Append to the Token on the top of the stack.
//Take into account the Token group mode
Token top = groupStack.Peek();
if (top.Group.Advance == GroupAdvanceMode.Token)
{
// Append all text
top.Data += read.Data;
lookAheadBuffer.Consume(read.Data.Length);
}
else
{
// Append one character
top.Data += read.Data[0].ToString();
lookAheadBuffer.Consume(1);
}
read.EndPosition = lookAheadBuffer.Position;
}
}
}
//This function implements the DFA for th parser's lexer.
//It generates a token which is used by the LALR state
//machine.
private Token LookAheadDFA(LookAheadBuffer lookAheadBuffer)
{
string ch = lookAheadBuffer.LookAhead(1);
if (String.IsNullOrEmpty(ch) || ch[0] == Char.MaxValue)
{
return new Token(egtDataManager.GetFirstSymbolOfType(SymbolType.End), String.Empty)
{
StartPosition = lookAheadBuffer.Position,
EndPosition = lookAheadBuffer.Position
};
}
int currentDFA = 0;
int lookAheadPosition = 1;
//Next byte in the input Stream
int lastAcceptState = -1;
//We have not yet accepted a character string
int lastAcceptPosition = -1;
while (true)
{
bool found = false;
ch = lookAheadBuffer.LookAhead(lookAheadPosition);
if (!String.IsNullOrEmpty(ch))
{
foreach (FAEdge edge in egtDataManager.GetFAState(currentDFA).Edges)
{
//Look for character in the Character Set Table
if (edge.Characters.Contains(ch[0]))
{
int target = edge.Target;
if (egtDataManager.GetFAState(target).Accept != null)
{
lastAcceptState = target;
lastAcceptPosition = lookAheadPosition;
}
currentDFA = target;
lookAheadPosition++;
found = true;
break;
}
}
}
if (!found)
{
Symbol symbol = null;
string data = String.Empty;
// Lexer cannot recognize symbol
if (lastAcceptState == -1)
{
symbol = egtDataManager.GetFirstSymbolOfType(SymbolType.Error);
data = lookAheadBuffer.GetTextFromBuffer(1);
}
else
{
symbol = egtDataManager.GetFAState(lastAcceptState).Accept;
data = lookAheadBuffer.GetTextFromBuffer(lastAcceptPosition);
}
return new Token(symbol, data)
{
StartPosition = lookAheadBuffer.Position
};
}
}
}
private bool DoReduction(Stack<Token> tokenStack, LookAheadBuffer lookAheadBuffer, ref ushort lalrState, LRAction parseAction)
{
Token head = null;
//Produce a reduction - remove as many tokens as members in the rule & push a nonterminal token
Production prod = egtDataManager.GetProduction(parseAction.Value);
bool reductionSkipped = false;
//Skip reduction?
if ((TrimReductions && prod.ConsistsOfOneNonTerminal())
|| (SkipEmptyProductions && prod.Handle.Count == 0))
{
head = tokenStack.Pop();
head.Symbol = prod.Head;
reductionSkipped = true;
}
//Build a Reduction
else
{
Reduction reduction = new Reduction(prod.Handle.Count, prod);
//If a production has no handles, it has no location.
//Set a would-be location instead.
if (prod.Handle.Count == 0)
{
reduction.StartPosition = reduction.EndPosition = lookAheadBuffer.Position;
}
else
{
for (int i = prod.Handle.Count - 1; i >= 0; i--)
{
reduction[i] = tokenStack.Pop();
}
}
head = reduction;
}
//If n is -1 here, then we have an Internal Table Error!!!
LRAction action = egtDataManager.GetLRActionList(tokenStack.Peek().State)[prod.Head];
if (action == null)
{
OnInternalError();
return false;
}
lalrState = action.Value;
head.State = lalrState;
tokenStack.Push(head);
if (!reductionSkipped)
{
OnReduction((Reduction)tokenStack.Peek());
}
return true;
}
public bool Parse(TextReader reader)
{
if (egtDataManager == null)
{
OnNotLoadedError();
return(false);
}
TokenQueueStack inputTokens = new TokenQueueStack();
Stack <Token> tokenStack = new Stack <Token>();
tokenStack.Push(new Token());
Stack <Token> groupStack = new Stack <Token>();
LookAheadBuffer lookAheadBuffer = new LookAheadBuffer(reader);
ushort lalrState = 0;
while (true)
{
if (inputTokens.Count == 0)
{
inputTokens.Push(ProduceToken(groupStack, lookAheadBuffer));
OnTokenRead(inputTokens.Peek());
}
//Runaway group
else if (groupStack.Count != 0)
{
OnGroupError();
return(false); //Error; abort
}
else
{
Token read = inputTokens.Peek();
switch (read.Type)
{
case SymbolType.Noise:
inputTokens.Pop();
break;
case SymbolType.Error:
OnLexicalError(read.EndPosition, read.Data);
return(false); //Error; abort
default:
LRActionList actionList = egtDataManager.GetLRActionList(lalrState);
LRAction parseAction = actionList[read.Symbol];
if (parseAction == null)
{
HandleSyntaxError(actionList, read);
return(false);
}
switch (parseAction.Type)
{
case LRActionType.Accept:
OnCompleted(tokenStack.Peek().Tag);
return(true);
case LRActionType.Shift:
lalrState = parseAction.Value;
read.State = lalrState;
tokenStack.Push(read);
//It now exists on the Token-Stack and must be eliminated from the queue.
inputTokens.Dequeue();
break;
case LRActionType.Reduce:
if (!DoReduction(tokenStack, lookAheadBuffer, ref lalrState, parseAction))
{
return(false);
}
break;
}
break;
}
}
}
}
private Token ProduceToken(Stack <Token> groupStack, LookAheadBuffer lookAheadBuffer)
{
while (true)
{
Token read = LookAheadDFA(lookAheadBuffer);
if (read.Type == SymbolType.GroupStart && (groupStack.Count == 0 || groupStack.Peek().Group.Nesting.Contains(read.Group.TableIndex)))
{
lookAheadBuffer.Consume(read.Data.Length);
read.EndPosition = lookAheadBuffer.Position;
groupStack.Push(read);
}
else if (groupStack.Count == 0)
{
//The token is ready to be analyzed.
lookAheadBuffer.Consume(read.Data.Length);
read.EndPosition = lookAheadBuffer.Position;
return(read);
}
else if (Object.ReferenceEquals(groupStack.Peek().Group.End, read.Symbol))
{
//End the current group
Token pop = groupStack.Pop();
if (pop.Group.Ending == GroupEndingMode.Closed)
{
pop.Data += read.Data;
lookAheadBuffer.Consume(read.Data.Length);
read.EndPosition = lookAheadBuffer.Position;
}
//We are out of the group. Return pop'd token (which contains all the group text)
if (groupStack.Count == 0)
{
//Change symbol to parent
pop.Symbol = pop.Group.Container;
return(pop);
}
else
{
groupStack.Peek().Data += pop.Data;
}
}
else if (read.Type == SymbolType.End)
{
return(read);
}
else
{
//We are in a group, Append to the Token on the top of the stack.
//Take into account the Token group mode
Token top = groupStack.Peek();
if (top.Group.Advance == GroupAdvanceMode.Token)
{
// Append all text
top.Data += read.Data;
lookAheadBuffer.Consume(read.Data.Length);
}
else
{
// Append one character
top.Data += read.Data[0].ToString();
lookAheadBuffer.Consume(1);
}
read.EndPosition = lookAheadBuffer.Position;
}
}
}
//This function implements the DFA for th parser's lexer.
//It generates a token which is used by the LALR state
//machine.
private Token LookAheadDFA(LookAheadBuffer lookAheadBuffer)
{
string ch = lookAheadBuffer.LookAhead(1);
if (String.IsNullOrEmpty(ch) || ch[0] == Char.MaxValue)
{
return(new Token(egtDataManager.GetFirstSymbolOfType(SymbolType.End), String.Empty)
{
StartPosition = lookAheadBuffer.Position,
EndPosition = lookAheadBuffer.Position
});
}
int currentDFA = 0;
int lookAheadPosition = 1;
//Next byte in the input Stream
int lastAcceptState = -1;
//We have not yet accepted a character string
int lastAcceptPosition = -1;
while (true)
{
bool found = false;
ch = lookAheadBuffer.LookAhead(lookAheadPosition);
if (!String.IsNullOrEmpty(ch))
{
foreach (FAEdge edge in egtDataManager.GetFAState(currentDFA).Edges)
{
//Look for character in the Character Set Table
if (edge.Characters.Contains(ch[0]))
{
int target = edge.Target;
if (egtDataManager.GetFAState(target).Accept != null)
{
lastAcceptState = target;
lastAcceptPosition = lookAheadPosition;
}
currentDFA = target;
lookAheadPosition++;
found = true;
break;
}
}
}
if (!found)
{
Symbol symbol = null;
string data = String.Empty;
// Lexer cannot recognize symbol
if (lastAcceptState == -1)
{
symbol = egtDataManager.GetFirstSymbolOfType(SymbolType.Error);
data = lookAheadBuffer.GetTextFromBuffer(1);
}
else
{
symbol = egtDataManager.GetFAState(lastAcceptState).Accept;
data = lookAheadBuffer.GetTextFromBuffer(lastAcceptPosition);
}
return(new Token(symbol, data)
{
StartPosition = lookAheadBuffer.Position
});
}
}
}
