static public Token LexNext()
{
int state = 0;
string value = string.Empty;
int startOffset = 0;
ErrorKind errorKind = ErrorKind.DEFAULT;
char? cQuestion;
char c;
while (true)
{
cQuestion = SourceViewModel.NextChar();
if (cQuestion.HasValue)
{
c = cQuestion.Value;
switch (state)
{
case 0:
startOffset = SourceViewModel.GetOffset();
if (char.IsLetter(c) || c == '_')
{
state = 1;
value += c;
break;
}
if (char.IsDigit(c))
{
state = 2;
value += c;
break;
}
if (char.IsWhiteSpace(c))
{
break;
}
if (c == '>')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.GT));
}
if (c == '+')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.ADD));;
}
if (c == '-')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.SUB));
}
if (c == '*')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.MULT));
}
if (c == '/')
{
state = 7;
value += c;
break;
}
if (c == '=')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.EQU));
}
if (c == '<')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.LT));
}
if (c == '{')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.LBRA));
}
if (c == '}')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.RBRA));
}
if (c == '(')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.LPAR));
}
if (c == ')')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.RPAR));
}
if (c == ';')
{
value = c.ToString();
return(new Token(startOffset, value, TokenKind.SEMI));
}
if (c == '.')
{
state = 4;
value += c;
errorKind = ErrorKind.NUMBERERROR;
break;
}
//ERROR
state = 4;
value += c;
errorKind = ErrorKind.INVALIDCHAR;
break;
case 1:
if (char.IsLetterOrDigit(c))
{
value += c;
break;
}
SourceViewModel.putBack();
if (KeyWords.ContainsKey(value))
{
return(new Token(startOffset, value, KeyWords[value]));
}
else
{
return(new Token(startOffset, value, TokenKind.ID));
}
case 2:
if (char.IsDigit(c))
{
value += c;
break;
}
if (c == '.')
{
state = 5;
value += c;
break;
}
SourceViewModel.putBack();
return(new Token(startOffset, value, TokenKind.NUM));
case 3:
if (c == '*')
{
state = 9;
}
value += c;
break;
case 4:
switch (errorKind)
{
case ErrorKind.NUMBERERROR:
if (char.IsDigit(c) || c == '.')
{
value += c;
}
else
{
SourceViewModel.putBack();
HandleError(startOffset, value, errorKind);
return(new Token(startOffset, value, TokenKind.ERROR));
}
break;
case ErrorKind.INVALIDCHAR:
if (char.IsLetterOrDigit(c) || symbols.Contains(c) || char.IsWhiteSpace(c))
{
SourceViewModel.putBack();
HandleError(startOffset, value, errorKind);
return(new Token(startOffset, value, TokenKind.ERROR));
}
else
{
value += c;
}
break;
default:
if (char.IsWhiteSpace(c))
{
HandleError(startOffset, value, errorKind);
return(new Token(startOffset, value, TokenKind.ERROR));
}
else
{
value += c;
}
break;
}
break;
case 5:
if (char.IsDigit(c))
{
state = 6;
value += c;
break;
}
if (c == '.')
{
state = 4;
value += c;
errorKind = ErrorKind.NUMBERERROR;
break;
}
SourceViewModel.putBack();
HandleError(startOffset, value, ErrorKind.NUMBERERROR);
return(new Token(startOffset, value, TokenKind.ERROR));
case 6:
if (char.IsDigit(c))
{
state = 6;
value += c;
break;
}
if (c == '.')
{
state = 4;
value += c;
errorKind = ErrorKind.NUMBERERROR;
break;
}
SourceViewModel.putBack();
return(new Token(startOffset, value, TokenKind.NUM));
case 7:
if (c == '*')
{
value += c;
state = 3;
break;
}
if (c == '/')
{
value += c;
state = 8;
break;
}
SourceViewModel.putBack();
return(new Token(startOffset, value, TokenKind.DIV));
case 8:
if (c == '\r' || c == '\n') //for the case "\r\n" and "\n";
{
return(new Token(startOffset, value, TokenKind.ANNO));
}
value += c;
break;
case 9:
if (c == '/')
{
value += c;
return(new Token(startOffset, value, TokenKind.ANNO));
}
value += c;
state = 3;
break;
}
}
else
{
switch (state)
{
case 0:
return(new Token(SourceViewModel.GetEndOffset(), value, TokenKind.END));
case 1:
if (KeyWords.ContainsKey(value))
{
return(new Token(startOffset, value, KeyWords[value]));
}
else
{
return(new Token(startOffset, value, TokenKind.ID));
}
case 2:
case 6:
return(new Token(startOffset, value, TokenKind.NUM));
case 3:
case 9:
HandleError(startOffset, value, ErrorKind.ANNONOTCLOSED);
return(new Token(startOffset, value, TokenKind.ERROR));
case 4:
HandleError(startOffset, value, errorKind);
return(new Token(startOffset, value, TokenKind.ERROR));
case 5:
HandleError(startOffset, value, ErrorKind.NUMBERERROR);
return(new Token(startOffset, value, TokenKind.ERROR));
case 7:
return(new Token(startOffset, value, TokenKind.DIV));
case 8:
return(new Token(startOffset, value, TokenKind.ANNO));
}
}
}
}
