///
/// Scans through the file and parses the next token it finds. It
/// returns the token, but also provides it as a property for
/// convenience.
///
/// An example:
///
/// // expecting an identifier
/// if (lexer.Scan().token != TokenType.Identifier)
/// {
/// Console.WriteLine("Expecting an identifier but found:");
/// lexer.PrintToken('!');
/// }
///
public Token Scan()
{
if (Buffer.Count > 0)
{
//Console.WriteLine("Found a buffered Token from last Scan: {0}", buffer.Peek().type);
_token = Buffer.Dequeue();
return _token;
}
Forward();
if (Buffer.Count > 0)
{
//Console.WriteLine("Found a buffered Token from Forward: {0}", buffer.Peek().type);
_token = Buffer.Dequeue();
return _token;
}
// if it's our first run, and we found something we need to start a statement
if (IsFirstRun)
{
//Console.WriteLine("Because it's our first time we're adding a StartStatement Token");
_token = CreateToken(TokenType.StartStatement, "");
IsFirstRun = false;
return _token;
}
_token.offset = Offset;
_token.column = Column;
_token.indent = Indent;
_token.line = Line;
_token.lexer = this;
_token.value = "Lexer Fell Through";
_token.length = 0;
_token.type = TokenType.Error;
// get the current character
char c = Source[Offset];
if (c == '"')
{
Offset++;
Column++;
while (Offset < Source.Length
&& (Source[Offset] != '"'
|| Source[Offset - 1] == '\\'))
{
Column++;
if (Source[Offset] == '\n')
{
// error
Line++;
Indent = 0;
Column = 0;
return Error("Newline within a string literal");
}
Offset++;
}
if (Offset >= Source.Length)
{
// error
Offset = Source.Length;
return Error("Reached the end of the file while in a string literal");
}
Offset++;
_token.length = Offset - _token.offset;
_token.value = "";
for (int i = 1; i < _token.length - 1; i++)
{
if (Source[_token.offset + i] == '\\'
&& _token.offset + i + 1 < Source.Length)
{
// remove the escaped character, anything not here just
// falls through, probably should be an error or warning
i++;
_token.value +=
Source[_token.offset + i] == '"' ? '"' :
Source[_token.offset + i] == '0' ? '\0' :
Source[_token.offset + i] == 'v' ? '\v' :
Source[_token.offset + i] == 'f' ? '\f' :
Source[_token.offset + i] == 'n' ? '\n' :
Source[_token.offset + i] == 't' ? '\t' :
Source[_token.offset + i] == 'b' ? '\b' :
Source[_token.offset + i] == 'r' ? '\r' :
Source[_token.offset + i] == 't' ? '\t' :
Source[_token.offset + i];
}
else
_token.value += Source[_token.offset + i];
}
_token.type = TokenType.String;
}
if (c == '\'')
{
Offset++;
Column++;
while (Offset < Source.Length
&& (Source[Offset] != '\''
|| Source[Offset - 1] == '\\'))
{
Column++;
if (Source[Offset] == '\n')
{
// error
Line++;
Indent = 0;
Column = 0;
return Error("Newline within a string literal");
}
Offset++;
}
if (Offset >= Source.Length)
{
// error
Offset = Source.Length;
return Error("Reached the end of the file while in a string literal");
}
Offset++;
_token.length = Offset - _token.offset;
for (int i = 1; i < _token.length - 1; i++)
{
if (Source[_token.offset + i] == '\\'
&& _token.offset + i + 1 < Source.Length)
{
// remove the escaped character, anything not here just
// falls through, probably should be an error or warning
i++;
_token.value +=
Source[_token.offset + i] == '\'' ? '\'' :
Source[_token.offset + i] == '0' ? '\0' :
Source[_token.offset + i] == 'v' ? '\v' :
Source[_token.offset + i] == 'f' ? '\f' :
Source[_token.offset + i] == 'n' ? '\n' :
Source[_token.offset + i] == 't' ? '\t' :
Source[_token.offset + i] == 'b' ? '\b' :
Source[_token.offset + i] == 'r' ? '\r' :
Source[_token.offset + i] == 't' ? '\t' :
Source[_token.offset + i];
}
else
_token.value += Source[_token.offset + i];
}
_token.type = TokenType.Character;
}
else if (Char.IsNumber(c))
{
// might be a number, but if it has letters afterwards it's an
// identifier eg 3DObject
while (Offset < Source.Length && Char.IsDigit(Source[Offset]))
Offset++;
if (Offset < Source.Length && Char.IsLetter(Source[Offset]))
{
// it's actually an identifier
while (Offset < Source.Length
&& (Char.IsLetterOrDigit(Source[Offset])
|| Source[Offset] == '_'))
Offset++;
_token.type = TokenType.Identifier;
CopyToken();
}
else if (Offset + 1 < Source.Length
&& (Source[Offset] == '.'
|| Char.IsDigit(Source[Offset + 1])))
{
// it's a decimal
Offset++;
while (Offset < Source.Length
&& Char.IsDigit(Source[Offset]))
Offset++;
_token.type = TokenType.Decimal;
CopyToken();
}
else
{
// it's an integer
_token.type = TokenType.Integer;
CopyToken();
}
}
else if (Char.IsLetter(c))
{
// it's an identifier
while (Offset < Source.Length
&& (Char.IsLetterOrDigit(Source[Offset])
|| Source[Offset] == '_'))
Offset++;
_token.type = TokenType.Identifier;
CopyToken();
}
else if (c == '<'
|| c == '>'
|| c == '='
|| c == '!'
|| c == '*'
|| c == '/'
|| c == '%')
{
// might have an equals afterwards
Offset++;
if (Offset < Source.Length && Source[Offset] == '=')
Offset++;
_token.type = TokenType.Symbol;
CopyToken();
}
else if (c == '+')
{
Offset++;
if (Offset < Source.Length
&& (Source[Offset] == '+' || Source[Offset] == '='))
Offset++;
_token.type = TokenType.Symbol;
CopyToken();
}
else if (c == '-')
{
Offset++;
if (Offset < Source.Length
&& (Source[Offset] == '-' || Source[Offset] == '='))
Offset++;
_token.type = TokenType.Symbol;
CopyToken();
}
else if (Offset + 1 < Source.Length
&& ((c == '&' && Source[Offset + 1] == '&')
|| (c == '|' && Source[Offset + 1] == '|')))
{
Offset += 2;
_token.type = TokenType.Symbol;
CopyToken();
}
else if (c == '.'
|| c == ','
|| c == ':'
|| c == ';'
|| c == '('
|| c == ')'
|| c == '['
|| c == ']')
{
Offset++;
_token.type = TokenType.Symbol;
CopyToken();
}
/* remember: take '[' out of the above list to put xml back in
else if (c == '[')
{
// special case, this can contain xml... yay!
offset++;
int xmlStart = offset;
while (xmlStart < source.Length
&& (source[xmlStart] == ' '
|| source[xmlStart] == '\n'
|| source[xmlStart] == '\t'))
xmlStart++;
if (xmlStart < source.Length && source[xmlStart] == '<')
{
// we have xml
token.offset = xmlStart;
offset = xmlStart + 1;
while (offset < source.Length)
{
if (source[offset] == '>')
{
offset++;
while (offset < source.Length
&& (source[offset] == ' '
|| source[offset] == '\n'
|| source[offset] == '\t'))
offset++;
if (offset < source.Length && source[offset] == ']')
{
// end of the xml... yay!
token.type = TokenType.XML;
CopyToken();
offset++;
break;
}
}
else
offset++;
}
if (offset >= source.Length)
return Error("Reached the end of the file while in an XML block");
}
else
{
token.type = TokenType.Symbol;
CopyToken();
}
}*/
else
{
// unknown character, print out some shiz and skip
PrintToken('!');
Offset++;
return Scan();
// unknown character, move on one
//offset++;
}
return _token;
}
///
/// Load from a string
///
public Lexer(string location, string source)
: base(location, source)
{
_token = new Token();
Buffer = new Queue<Token>();
}
public string PrintToken(char icon, Token token)
{
int start = token.offset;
int end = token.offset + token.length;
start = Math.Min(start, Source.Length - 1);
end = Math.Min(end, Source.Length - 1);
while (start > 0 && Source[start - 1] != '\n')
start--;
while (start < Source.Length
&& (Source[start] == '\t' || Source[start] == ' '))
start++;
while (end < Source.Length && Source[end] != '\n')
end++;
return String.Format("{0} {1}:{2} {3}\n {4}\n {5}{6}",
icon, Filename,
token.line, token.type,
Source.Substring(start, end - start),
new String(' ', token.offset - start),
new String('^', Math.Max(token.length, 1)));
}