private static Token NextTokenFromArg(string s, ref int idx)
{
switch (state)
{
case ScannerState.NeedsNextBare:
state = ScannerState.InBareArg;
break;
case ScannerState.NeedsNextQuote:
tokenBuilder.Append(' ');
state = ScannerState.InQuoteString;
break;
case ScannerState.InShortArg:
tokenBuilder.Length = 0;
break;
default:
state = ScannerState.Unstarted;
tokenBuilder.Length = 0;
break;
}
Token token;
while (idx < s.Length)
{
char c = s[idx];
switch (state)
{
case ScannerState.Unstarted:
switch (c)
{
case tokenOptionChar:
state = ScannerState.InOptionToken;
idx++;
break;
case doubleQuoteChar:
case singleQuoteChar:
idx++;
state = ScannerState.InQuoteString;
break;
default:
state = ScannerState.InBareArg;
break;
}
break;
case ScannerState.InOptionToken:
switch (c)
{
case tokenOptionChar:
state = ScannerState.InLongArg;
idx++;
break;
default:
if (Char.IsWhiteSpace(c))
{
// If we get a single '-' followed by whitespace, figure it's a bare arg
// (like a stdin placeholder).
idx++;
return(new Token(TokenType.BareArg, c));
}
else
{
state = ScannerState.InShortArg;
}
break;
}
break;
case ScannerState.InShortArg:
if (Char.IsLetterOrDigit(c))
{
idx++;
return(new Token(TokenType.ShortOption, c));
}
else
{
throw new Exception(string.Format(
"Unexpected character '{0}' at position {1}. Short options must be letters or digits.",
c,
idx
));
}
case ScannerState.InLongArg:
if (Char.IsWhiteSpace(c) || c == assignmentOpChar)
{
idx++;
// The token is done, return it.
token = new Token(TokenType.LongOption, tokenBuilder.ToString());
tokenBuilder.Length = 0;
return(token);
}
else
{
// Keep adding string data to the token.
tokenBuilder.Append(c);
idx++;
}
break;
case ScannerState.InQuoteString:
switch (c)
{
case doubleQuoteChar:
case singleQuoteChar:
idx++;
return(new Token(TokenType.BareArg, tokenBuilder.ToString()));
case escapeNextChar:
state = ScannerState.InEscapeChar;
escapeReturnState = ScannerState.InQuoteString;
break;
default:
idx++;
tokenBuilder.Append(c);
break;
}
break;
case ScannerState.InBareArg:
switch (c)
{
case escapeNextChar:
state = ScannerState.InEscapeChar;
escapeReturnState = ScannerState.InBareArg;
break;
default:
// Keep adding string data to the token until the end of the arg.
tokenBuilder.Append(c);
idx++;
break;
}
break;
case ScannerState.InEscapeChar:
string escapeSeq = s.SafeSubstring(idx, 5);
if (idx == (s.Length - 1))
{
escapeSeq = string.Concat(escapeSeq, ' ');
state = ScannerState.NeedsNextBare;
}
else
{
state = escapeReturnState;
}
try {
int unescapedLen = escapeSeq.Length;
escapeSeq = Regex.Unescape(escapeSeq);
int escapedLen = unescapedLen - escapeSeq.Length;
idx += escapedLen;
tokenBuilder.Append(escapeSeq[0]);
}
catch (ArgumentException) {
tokenBuilder.Append(c);
}
idx++;
break;
}
}
// If we get here, we've hit the end of the string.
// If the token builder has zero length, something is malformed.
if (tokenBuilder.Length < 1)
{
throw new Exception(string.Format("Unexpected end of arg while parsing {0}.", state.ToString()));
}
switch (state)
{
case ScannerState.InQuoteString:
state = ScannerState.NeedsNextQuote;
return(new Token());
case ScannerState.NeedsNextBare:
return(new Token());
case ScannerState.InBareArg:
return(new Token(TokenType.BareArg, tokenBuilder.ToString()));
case ScannerState.InShortArg:
return(new Token(TokenType.ShortOption, tokenBuilder.ToString()));
case ScannerState.InLongArg:
return(new Token(TokenType.LongOption, tokenBuilder.ToString()));
default:
throw new Exception(string.Format("Unexpected end of arg while parsing {0}.", state.ToString()));
}
}
