private static int _scanHtmlTagOpenTag(string s, int pos, int sourceLength)
{
var lastPosition = sourceLength - 1;
// the minimum length valid tag is "a>"
if (lastPosition < pos + 1)
{
return(0);
}
// currentPosition - positioned after the last character matched by that any particular part
var currentPosition = pos;
// stores the character at the current position
char currentChar = s[currentPosition];
// stores if the previous character was a whitespace
bool hadWhitespace = false;
// stores if an attribute name has been parsed
bool hadAttribute = false;
// some additional variables used in the process
char c1;
// The tag name must start with an ASCII letter
if (!ScannerCharacterMatcher.MatchAsciiLetter(s, ref currentChar, ref currentPosition, lastPosition))
{
return(0);
}
// Move past any other characters that make up the tag name
ScannerCharacterMatcher.MatchHtmlTagNameCharacter(s, ref currentChar, ref currentPosition, lastPosition);
// loop while the end of string is reached or the tag is closed
while (currentPosition <= lastPosition)
{
// Move past any whitespaces
hadWhitespace = ScannerCharacterMatcher.MatchWhitespaces(s, ref currentChar, ref currentPosition, lastPosition);
// check if the end of the tag has been reached
if (currentChar == '>')
{
return(currentPosition - pos + 1);
}
if (currentChar == '/')
{
if (currentPosition == lastPosition)
{
return(0);
}
currentChar = s[++currentPosition];
return((currentChar == '>') ? currentPosition - pos + 1 : 0);
}
// check if arrived at the attribute value
if (currentChar == '=')
{
if (!hadAttribute || currentPosition == lastPosition)
{
return(0);
}
// move past the '=' symbol and any whitespaces
currentChar = s[++currentPosition];
ScannerCharacterMatcher.MatchWhitespaces(s, ref currentChar, ref currentPosition, lastPosition);
if (currentChar == '\'' || currentChar == '\"')
{
c1 = currentChar;
currentChar = s[++currentPosition];
ScannerCharacterMatcher.MatchAnythingExcept(s, ref currentChar, ref currentPosition, lastPosition, c1);
if (currentChar != c1 || currentPosition == lastPosition)
{
return(0);
}
currentChar = s[++currentPosition];
}
else
{
// an unquoted value must have at least one character
if (!ScannerCharacterMatcher.MatchAnythingExceptWhitespaces(s, ref currentChar, ref currentPosition, lastPosition, '\"', '\'', '=', '<', '>', '`'))
{
return(0);
}
}
hadAttribute = false;
continue;
}
// the attribute must be preceded by a whitespace
if (!hadWhitespace)
{
return(0);
}
// if the end has not been found then there is just one possible alternative - an attribute
// validate that the attribute name starts with a correct character
if (!ScannerCharacterMatcher.MatchAsciiLetter(s, ref currentChar, ref currentPosition, lastPosition, '_', ':'))
{
return(0);
}
// match any remaining characters in the attribute name
ScannerCharacterMatcher.MatchAsciiLetterOrDigit(s, ref currentChar, ref currentPosition, lastPosition, '_', ':', '.', '-');
hadAttribute = true;
}
return(0);
}
