/*
* Expect functions return Lexemes of the tokens they expect.
* If the input contains any unexpected characters,
* an exception is thrown.
*
* Expected regular definition: comment
*/
// comment := "/*" commentend
// commentend := ([^/][^*] | comment)* "*/"
public Lexeme ExpectBlockComment()
{
InputBuffer.Position pos = input.GetPosition();
if (!ExpectToken("/*")) // block comment start
{
throw new LexerException("blockcomment expected", pos);
}
string s = "";
int nestedComments = 0; // counter for level of comment nesting
if (input.HasCharacter())
{
do
{
if (input.HasNextCharacter() && input.PeekCharacter() == '/' && input.PeekNext() == '*')
{
// nested comment start found
// read /*
s += input.PeekCharacter();
if (input.Next())
{
s += input.PeekCharacter();
}
++nestedComments;
continue;
}
if (input.HasNextCharacter() && input.PeekCharacter() == '*' && input.PeekNext() == '/')
{
// comment end found
if (nestedComments <= 0)
{
// the end is final comment end
// skip */
input.Next();
input.Next();
return(new Lexeme(TokenType.BLOCKCOMMENT, pos, s));
}
// the end is nested
// read */
s += input.PeekCharacter();
if (input.Next())
{
s += input.PeekCharacter();
}
--nestedComments;
continue;
}
s += input.PeekCharacter();
} while (input.Next());
}
throw new LexerException(string.Format("unexpected end of blockcomment starting at {0}", pos.ToString()), input.GetPosition());
}
/*
* Expect functions return Lexemes of the tokens they expect.
* If the input contains any unexpected characters,
* an exception is thrown.
*
* Expected regex: "(\\[^\n]|[^"\n])*"
*/
public Lexeme ExpectString()
{
InputBuffer.Position pos = input.GetPosition();
if (!ExpectToken("\"")) // Expect string starting quote
{
throw new LexerException("string expected", pos);
}
string s = "";
if (input.HasCharacter())
{
do
{
if (input.PeekCharacter() == '\n') // unexpected newline in middle of string
{
break;
}
if (input.PeekCharacter() == '\\') // escaped character
{
// skip escape character
if (!input.Next())
{
break; // end of input after escape character
}
// handle escaped character
switch (input.PeekCharacter())
{
case 'n': s += '\n'; break;
case 't': s += '\t'; break;
case '"': s += '"'; break;
default:
throw new LexerException(
string.Format("unrecognized escape character {0}", input.PeekCharacter()),
input.GetPosition()
);
}
continue;
}
if (input.PeekCharacter() == '"') // string end quote
{
input.Next();
return(new Lexeme(TokenType.STRING, pos, s));
}
s += input.PeekCharacter();
} while (input.Next());
}
throw new LexerException(string.Format("unexpected end of string starting at {0}", pos.ToString()), input.GetPosition());
}