public Lexer()
{
error = Enums.LexerError.NONE;
tokenList = new TokenList();
code = "";
currentSymbol = '\0';
charIndex = 0;
lineNum = 1;
}
public TokenList Run(string inputCode)
{
if (inputCode == "")
{
error = Enums.LexerError.NO_SOURCE_CODE;
return(null);
}
code = inputCode + '\0';
currentSymbol = code[0];
while (true)
{
// Terminate loop is an error has been found
if (HasError())
{
break;
}
// Remove whitespace (also increments line number)
RemoveWhitespace();
// Terminate loop if end of string is reached
if (currentSymbol == '\0')
{
break;
}
// Handle symbol based on its type
switch (GetSymbolType(currentSymbol))
{
case (int)Enums.CharacterType.ALPHA:
HandleAlpha();
break;
case (int)Enums.CharacterType.DIGIT:
HandleDigit();
break;
case (int)Enums.CharacterType.SPECIAL:
HandleSpecial();
break;
case (int)Enums.CharacterType.INVALID:
error = Enums.LexerError.INV_SYM;
break;
}
}
return(tokenList);
}
private void HandleDigit()
{
int numDigits = 0;
StringBuilder sb = new StringBuilder();
bool continueLooping = true;
while (continueLooping)
{
switch (GetSymbolType(currentSymbol))
{
case (int)Enums.CharacterType.ALPHA:
error = Enums.LexerError.NONLETTER_VAR_INITIAL;
// error
return;
case (int)Enums.CharacterType.DIGIT:
if (numDigits < Constants.MaxNumberSize)
{
sb.Append(currentSymbol);
numDigits++;
NextSymbol();
}
else
{
error = Enums.LexerError.NUM_TOO_LONG;
return;
}
break;
case (int)Enums.CharacterType.SPECIAL:
case (int)Enums.CharacterType.INVALID:
continueLooping = false;
break;
}
}
Token newToken = new Token
{
lexeme = sb.ToString(),
id = Enums.TokenType.numbersym,
lineNum = lineNum
};
tokenList.Add(newToken);
}
private void HandleAlpha()
{
int numAlphanumerics = 0;
StringBuilder sb = new StringBuilder();
bool continueLooping = true;
while (continueLooping)
{
switch (GetSymbolType(currentSymbol))
{
case (int)Enums.CharacterType.ALPHA:
case (int)Enums.CharacterType.DIGIT:
if (numAlphanumerics < Constants.MaxIdentSize)
{
sb.Append(currentSymbol);
numAlphanumerics++;
NextSymbol();
}
else
{
error = Enums.LexerError.NAME_TOO_LONG;
return;
}
break;
case (int)Enums.CharacterType.SPECIAL:
case (int)Enums.CharacterType.INVALID:
continueLooping = false;
break;
}
}
Token newToken = new Token();
newToken.id = CheckReservedWords(sb.ToString());
if (newToken.id == Enums.TokenType.identsym)
{
newToken.lexeme = sb.ToString();
}
newToken.lineNum = lineNum;
tokenList.Add(newToken);
}
private void HandleSpecial()
{
Enums.TokenType id = Enums.TokenType.nulsym;
char lookaheadSymbol = code[charIndex + 1];
if ((currentSymbol == '/') && (lookaheadSymbol == '*'))
{
while (true)
{
NextSymbol();
if (currentSymbol == '\0')
{
error = Enums.LexerError.COMMENT_NOT_CLOSED;
return;
}
if (currentSymbol == '\n')
{
lineNum++;
}
lookaheadSymbol = code[charIndex + 1];
// Stop ignoring symbols when we reach the end of comment symbols */
if ((currentSymbol == '*') && (lookaheadSymbol == '/'))
{
break;
}
}
// Skip the end of comment symbols */
NextSymbol();
NextSymbol();
return;
}
else if ((currentSymbol == '<') && (lookaheadSymbol == '>'))
{
id = Enums.TokenType.neqsym;
NextSymbol();
}
else if ((currentSymbol == '<') && (lookaheadSymbol == '='))
{
id = Enums.TokenType.leqsym;
NextSymbol();
}
else if ((currentSymbol == '>') && (lookaheadSymbol == '='))
{
id = Enums.TokenType.geqsym;
NextSymbol();
}
else if ((currentSymbol == ':') && (lookaheadSymbol == '='))
{
id = Enums.TokenType.becomessym;
NextSymbol();
}
else
{
switch (currentSymbol)
{
case '+':
id = Enums.TokenType.plussym;
break;
case '-':
id = Enums.TokenType.minussym;
break;
case '*':
id = Enums.TokenType.multsym;
break;
case '/':
id = Enums.TokenType.slashsym;
break;
case '(':
id = Enums.TokenType.lparentsym;
break;
case ')':
id = Enums.TokenType.rparentsym;
break;
case '<':
id = Enums.TokenType.lessym;
break;
case '>':
id = Enums.TokenType.gtrsym;
break;
case '.':
id = Enums.TokenType.periodsym;
break;
case ';':
id = Enums.TokenType.semicolonsym;
break;
case ',':
id = Enums.TokenType.commasym;
break;
case '=':
id = Enums.TokenType.eqsym;
break;
}
}
NextSymbol();
Token newToken = new Token
{
id = id,
lineNum = lineNum
};
tokenList.Add(newToken);
}
