public void Init(string input)
{
this.Input = input;
StartPos = 0;
EndPos = 0;
CurrentLine = 0;
CurrentColumn = 0;
CurrentPosition = 0;
Skipped = new List<Token>();
LookAheadToken = null;
}
private List<TokenType> SkipList; // tokens to be skipped
public Scanner()
{
Regex regex;
Patterns = new Dictionary<TokenType, Regex>();
Tokens = new List<TokenType>();
LookAheadToken = null;
SkipList = new List<TokenType>();
#if SILVERLIGHT
RegexOptions ropt = RegexOptions.None;
#else
RegexOptions ropt = RegexOptions.Compiled;
#endif
regex = new Regex(@"[^\(\)!\|\+-]+", ropt);
Patterns.Add(TokenType.STATE, regex);
Tokens.Add(TokenType.STATE);
regex = new Regex(@"\|", ropt);
Patterns.Add(TokenType.INTERSECTION, regex);
Tokens.Add(TokenType.INTERSECTION);
regex = new Regex(@"\+", ropt);
Patterns.Add(TokenType.UNION, regex);
Tokens.Add(TokenType.UNION);
regex = new Regex(@"-", ropt);
Patterns.Add(TokenType.DIFFERENCE, regex);
Tokens.Add(TokenType.DIFFERENCE);
regex = new Regex(@"!", ropt);
Patterns.Add(TokenType.COMPLEMENT, regex);
Tokens.Add(TokenType.COMPLEMENT);
regex = new Regex(@"\(", ropt);
Patterns.Add(TokenType.BROPEN, regex);
Tokens.Add(TokenType.BROPEN);
regex = new Regex(@"\)", ropt);
Patterns.Add(TokenType.BRCLOSE, regex);
Tokens.Add(TokenType.BRCLOSE);
regex = new Regex(@"^$", ropt);
Patterns.Add(TokenType.EOF, regex);
Tokens.Add(TokenType.EOF);
}
/// <summary>
/// executes a lookahead of the next token
/// and will advance the scan on the input string
/// </summary>
/// <returns></returns>
public Token Scan(params TokenType[] expectedtokens)
{
Token tok = LookAhead(expectedtokens); // temporarely retrieve the lookahead
LookAheadToken = null; // reset lookahead token, so scanning will continue
StartPos = tok.EndPos;
EndPos = tok.EndPos; // set the tokenizer to the new scan position
return tok;
}
public Token GetToken(TokenType type)
{
Token t = new Token(this.StartPos, this.EndPos);
t.Type = type;
return t;
}
public void UpdateRange(Token token)
{
if (token.StartPos < startpos) startpos = token.StartPos;
if (token.EndPos > endpos) endpos = token.EndPos;
}
/// <summary>
/// returns token with longest best match
/// </summary>
/// <returns></returns>
public Token LookAhead(params TokenType[] expectedtokens)
{
int i;
int startpos = StartPos;
Token tok = null;
List<TokenType> scantokens;
// this prevents double scanning and matching
// increased performance
if (LookAheadToken != null
&& LookAheadToken.Type != TokenType._UNDETERMINED_
&& LookAheadToken.Type != TokenType._NONE_) return LookAheadToken;
// if no scantokens specified, then scan for all of them (= backward compatible)
if (expectedtokens.Length == 0)
scantokens = Tokens;
else
{
scantokens = new List<TokenType>(expectedtokens);
scantokens.AddRange(SkipList);
}
do
{
int len = -1;
TokenType index = (TokenType)int.MaxValue;
string input = Input.Substring(startpos);
tok = new Token(startpos, EndPos);
for (i = 0; i < scantokens.Count; i++)
{
Regex r = Patterns[scantokens[i]];
Match m = r.Match(input);
if (m.Success && m.Index == 0 && ((m.Length > len) || (scantokens[i] < index && m.Length == len )))
{
len = m.Length;
index = scantokens[i];
}
}
if (index >= 0 && len >= 0)
{
tok.EndPos = startpos + len;
tok.Text = Input.Substring(tok.StartPos, len);
tok.Type = index;
}
else
{
if (tok.StartPos < tok.EndPos - 1)
tok.Text = Input.Substring(tok.StartPos, 1);
}
if (SkipList.Contains(tok.Type))
{
startpos = tok.EndPos;
Skipped.Add(tok);
}
}
while (SkipList.Contains(tok.Type));
LookAheadToken = tok;
return tok;
}
