public Regex GetCachedRegex(CommentToken token)
{
// Cache the compiled Regex instances so we can reuse them even across different languages and file extensions.
// This is an important performance optimization for common delimiters like "//" and "/* */".
string regexCacheKey = this.id + ' ' + token.Text + ' ' + (token.IsCaseSensitive ? '+' : '-');
Regex result = RegexCache.GetOrAdd(regexCacheKey, key => this.CreateRegex(token));
return(result);
}
private Regex CreateRegex(CommentToken token)
{
StringBuilder sb = new StringBuilder();
if (!string.IsNullOrEmpty(this.begin))
{
// Allow optional whitespace after the comment begins.
sb.Append(Regex.Escape(this.begin)).Append(@"[ \t]*");
}
else
{
// If there's no begin delimiter (e.g., in a PlainText file), then start from
// the beginning of the line or require a non-word character before the token.
// https://msdn.microsoft.com/en-us/library/20bw873z.aspx#WordCharacter
sb.Append(@"(^|[^\w])");
}
// Begin a named group to get the comment text.
sb.Append("(?<" + RegexCommentGroupName + ">");
if (token.IsCaseSensitive)
{
sb.Append("(?-i:");
}
sb.Append(Regex.Escape(token.Text));
if (token.IsCaseSensitive)
{
sb.Append(")");
}
// Support an optional colon, space, or tab followed by any sequence of characters.
// But we also have to support simple comments like "-- TODO" or "(* TODO *)".
const string SeparatorPattern = @"[: \t]+.*";
if (string.IsNullOrEmpty(this.end))
{
// Close the optional separator and the named group then match to the end of the string.
sb.Append("(").Append(SeparatorPattern).Append(")?)$");
}
else
{
// Support an optional separator pattern ending with the lazy match token (?) so .* won't match
// to the end of the string if the end delimiter is matched first. Then close the optional separator
// and the named group and then match to the end of the string or to the end delimiter.
// http://stackoverflow.com/a/6738624/1882616 and http://www.regular-expressions.info/repeat.html
sb.Append(@"(").Append(SeparatorPattern).Append("?)?)($|").Append(Regex.Escape(this.end)).Append(")");
}
// Ignore case overall because even in case-sensitive languages, most tokens need to be match case-insensitively.
// Also, in some languages the case for comment delimiters needs to be ignored (e.g., REM in .bat files).
// The options for Compiled and CultureInvariant are just to make it match as fast as possible.
string regexPattern = sb.ToString();
Regex result = new Regex(regexPattern, RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.CultureInvariant);
return(result);
}
public IEnumerable <Regex> GetTokenRegexes(CommentToken token, bool preferSingleLineOnly)
{
IEnumerable <Delimiter> preferredDelimiters = preferSingleLineOnly && this.delimiters.Any(d => d.IsSingleLine)
? this.delimiters.Where(d => d.IsSingleLine)
: this.delimiters;
foreach (Delimiter delimiter in preferredDelimiters)
{
yield return(delimiter.GetCachedRegex(token));
}
}
public IEnumerable <Regex> GetTokenRegexes(CommentToken token)
{
IEnumerable <Regex> result = this.GetTokenRegexes(token, false);
return(result);
}
