internal static int GetEntityTagLength(string input, int startIndex, out EntityTagHeaderValue parsedValue)
{
Contract.Requires(startIndex >= 0);
parsedValue = null;
if (string.IsNullOrEmpty(input) || (startIndex >= input.Length))
{
return(0);
}
// Caller must remove leading whitespace. If not, we'll return 0.
bool isWeak = false;
int current = startIndex;
char firstChar = input[startIndex];
if (firstChar == '*')
{
// We have '*' value, indicating "any" ETag.
parsedValue = Any;
current++;
}
else
{
// The RFC defines 'W/' as prefix, but we'll be flexible and also accept lower-case 'w'.
if ((firstChar == 'W') || (firstChar == 'w'))
{
current++;
// We need at least 3 more chars: the '/' character followed by two quotes.
if ((current + 2 >= input.Length) || (input[current] != '/'))
{
return(0);
}
isWeak = true;
current++; // we have a weak-entity tag.
current = current + HttpRuleParser.GetWhitespaceLength(input, current);
}
int tagStartIndex = current;
int tagLength = 0;
if (HttpRuleParser.GetQuotedStringLength(input, current, out tagLength) != HttpParseResult.Parsed)
{
return(0);
}
parsedValue = new EntityTagHeaderValue();
if (tagLength == input.Length)
{
// Most of the time we'll have strong ETags without leading/trailing whitespace.
Debug.Assert(startIndex == 0);
Debug.Assert(!isWeak);
parsedValue._tag = input;
parsedValue._isWeak = false;
}
else
{
parsedValue._tag = input.Substring(tagStartIndex, tagLength);
parsedValue._isWeak = isWeak;
}
current = current + tagLength;
}
current = current + HttpRuleParser.GetWhitespaceLength(input, current);
return(current - startIndex);
}
