public void SetEndPosition(Lexer lexer)
{
EndLine = lexer[0, false].Line;
LexerToken token = lexer[0, false];
EndLinePos = token.LinePos + (token.Token == null ? 0 : token.Token.Length);
}
/// <summary> Gets the symbol the specified number of tokens ahead without advancing the current token. </summary>
/// <remarks> If the token is not a symbol, returns an empty string. </remarks>
public LexerToken PeekToken(int count)
{
LexerToken token = this[count];
if (token.Type == TokenType.Error)
{
throw token.Error;
}
return(token);
}
/// <summary> The token a specific number of tokens ahead of the current token. </summary>
public LexerToken this[int index, bool checkActive]
{
get
{
System.Diagnostics.Debug.Assert(index < LookAheadCount, "Lexer look ahead attempt exceeds maximum");
LexerToken token = _tokens[(_currentIndex + index) % LookAheadCount];
if (checkActive && (token.Type == TokenType.Unknown))
{
throw new LexerException(LexerException.Codes.NoActiveToken);
}
return(token);
}
}
/// <remarks> It is an error to access the current TokenType until <see cref="NextToken"/> has been called. </remarks>
public Lexer(string input)
{
_tokenizer = new Tokenizer(input);
for (int i = 0; i < LookAheadCount; i++)
{
_tokens[i] = new LexerToken();
}
for (int i = 0; i < (LookAheadCount - 1); i++)
{
if (!ReadNext(i))
{
break;
}
}
}
/// <summary>Advances the current token.</summary>
/// <returns>Returns the now active token.</returns>
public LexerToken NextToken()
{
ReadNext(_currentIndex);
_currentIndex = (_currentIndex + 1) % LookAheadCount;
LexerToken token = _tokens[_currentIndex];
if (token.Type == TokenType.EOF)
{
throw new LexerException(LexerException.Codes.UnexpectedEOF);
}
if (token.Type == TokenType.Error)
{
throw token.Error;
}
return(token);
}
/// <summary> Gets the symbol the specified number of tokens ahead without advancing the current token. </summary>
/// <remarks> If the token is not a symbol, returns an empty string. </remarks>
public string PeekTokenSymbol(int count)
{
LexerToken token = this[count];
if (token.Type == TokenType.Symbol)
{
return(token.Token);
}
else if (token.Type == TokenType.Error)
{
throw token.Error;
}
else
{
return(String.Empty);
}
}
/// <summary> Reads the next token into the specified location within the buffer. </summary>
/// <returns> True if the read token type is not EOF. </returns>
private bool ReadNext(int index)
{
LexerToken token = _tokens[index];
try
{
token.Type = _tokenizer.NextToken();
token.Token = _tokenizer.Token;
}
catch (Exception exception)
{
token.Type = TokenType.Error;
token.Error = exception;
}
token.Line = _tokenizer.Line;
token.LinePos = _tokenizer.LinePos;
return((token.Type != TokenType.EOF) && (token.Type != TokenType.Error));
}