/// <summary>
/// Prepares an <see cref="TerminalReader"/> to read from the specified <see cref="String"/>.
/// </summary>
/// <param name="text">A <see cref="String"/> containing the input text to be processed by the <see cref="TerminalReader"/>.</param>
public void Open(string text)
{
_text = text;
_match = null;
_queuedTerminal = null;
_stopTerminalRead = false;
}
/// <summary>
/// Returns the specified <see cref="Terminal"/> to the input stream.
/// </summary>
/// <param name="terminal">A <see cref="Terminal"/> to be returned to the input stream.</param>
public void PushTerminal(Terminal terminal)
{
if (_queuedTerminal != null)
{
throw new InvalidOperationException("Queued terminal already exists.");
}
_queuedTerminal = terminal;
}
/// <summary>
/// Returns the next <see cref="Terminal"/> in the input text without advancing the current position of the <see cref="TerminalReader"/>.
/// </summary>
/// <returns>The next <see cref="Terminal"/> in the input text. If no <see cref="TerminalType"/> recognizes the input text, <value>null</value> is returned.</returns>
public Terminal PeekTerminal()
{
if (m_queuedTerminal == null)
{
m_queuedTerminal = GetNextTerminal();
}
return m_queuedTerminal;
}
/// <summary>
/// Reads the next <see cref="Terminal"/>.
/// </summary>
/// <returns>The next <see cref="Terminal"/> in the input text. If no <see cref="TerminalType"/> recognizes the input text, <value>null</value> is returned.</returns>
public Terminal ReadTerminal()
{
Terminal result;
if (_queuedTerminal != null)
{
result = _queuedTerminal;
_queuedTerminal = null;
}
else
{
result = GetNextTerminal();
}
LinguaTrace.TraceEvent(TraceEventType.Information, LinguaTraceId.ID_PARSE_READTOKEN, "{0}", result);
return result;
}
/// <summary>
/// Returns the next <see cref="Terminal"/> in the input text without advancing the current position of the <see cref="TerminalReader"/>.
/// </summary>
/// <returns>The next <see cref="Terminal"/> in the input text. If no <see cref="TerminalType"/> recognizes the input text, <value>null</value> is returned.</returns>
public Terminal PeekTerminal()
{
return _queuedTerminal ?? (_queuedTerminal = GetNextTerminal());
}
/// <summary>
/// Performs syntax analysis against a sequence of terminals according to the <see cref="Grammar"/> used to create the <see cref="Parser"/>.
/// </summary>
/// <param name="terminalReader">Retrieves a sequence of <see cref="Terminal"/> objects.</param>
/// <returns>If syntax analysis succeeds, returns the <see cref="Nonterminal"/> associated with <see cref="Grammar.StartNonterminal"/>. Otherwise, <value>null</value> is returned.</returns>
public Nonterminal Parse(ITerminalReader terminalReader)
{
ParserStack stack = new ParserStack();
stack.Push(null, InitialState);
Terminal terminal = terminalReader.ReadTerminal();
while (terminal != null)
{
if (terminal.ElementType.Ignore)
{
terminal = terminalReader.ReadTerminal();
}
else
{
ParserAction action = stack.Peek().State.GetAction(terminal.ElementType);
LinguaTrace.TraceEvent(TraceEventType.Information, LinguaTraceId.ID_PARSE_ACTION, "{0}", action);
if (action == null)
{
return(null);
}
switch (action.ActionType)
{
case ParserActionTypes.Accept:
{
ParserActionAccept reduce = (ParserActionAccept)action;
RuleType rule = reduce.Rule;
Nonterminal lhs = Reduce(stack, rule);
return(lhs);
}
case ParserActionTypes.Shift:
{
ParserActionShift shift = (ParserActionShift)action;
stack.Push(terminal, shift.State);
terminal = terminalReader.ReadTerminal();
}
break;
case ParserActionTypes.Reduce:
{
ParserActionReduce reduce = (ParserActionReduce)action;
RuleType rule = reduce.Rule;
Nonterminal lhs = Reduce(stack, rule);
// Push the LHS nonterminal on the stack.
//
stack.Push(lhs, stack.Peek().State.GetGoto(lhs.ElementType));
}
break;
default:
throw new InvalidOperationException(string.Format("Unrecognized action type {0}.", action.ActionType));
}
}
}
;
return(null);
}
