public override void Flush()
{
if (!string.IsNullOrEmpty(UnwrittenCharactersFromPreviousCall))
{
string finalContentToWrite = UnwrittenCharactersFromPreviousCall;
if (BodyEndRegex.IsMatch(UnwrittenCharactersFromPreviousCall))
{
// apparently we did seem to match a </body> tag, which means we can replace the last match with our HTML snippet
finalContentToWrite = BodyEndRegex.Replace(UnwrittenCharactersFromPreviousCall, HtmlSnippet, 1);
}
else
{
// there was no </body> tag found, so we write down a warning to the log
Logger.Warn("Unable to locate '</body>' with content encoding '{0}' for request '{1}'. The response may be compressed or the markup may actually be missing a '</body>' tag. See {2} for information on troubleshooting this issue.", ContentEncoding.EncodingName, CurrentRequestRawUrl, TroubleshootingDocsUri);
}
// either way, if a replacement has been done or a warning has been written to the logs, the remaining unwritten characters must be written to the output stream
WriteToOutputStream(finalContentToWrite);
}
OutputStream.Flush();
}
public override void Write(byte[] buffer, int offset, int count)
{
// There are different cases we need to deal with
// Normally you would expect the contentInBuffer to contain the complete HTML code to return, but this is not always true because it is possible that
// the content that will be send back is larger than the buffer foreseen by ASP.NET (currently the buffer seems to be a little bit less than 16K)
// and in that case this method will be called multiple times, which might result in false positives being written to the logs for not finding a </body>
// in the current chunk.
// So we need to be able to deal with the following cases without writing those false positives
// 1 - the </body> tag is found
// 2 - the </body> tag was not found because
// 2.1 - the </body> tag will be available in one of the next calls because the total length of the output is larger than 16K
// 2.2 - the </body> tag is split up between this buffer and the next e.g.: "</bo" en "dy>"
// 2.3 - the </body> tag will never be available (is missing)
// 2.4 - Multiple </body> tags are available of which some might be part of a Javascript string or the markup is badly formatted
// The easiest way to deal with this is to look for the last match for the </body> tag and if it is found we write everything before it to the
// output stream and keep that </body> tag and everything that follows it (normally only a </html> tag but it can also be a 2.4 case) for the next call.
// In case there is no match for the </body> tag, then we write everything to the output stream except for the last 10 characters (normally the last 6 would suffice, but we take a little margin to reassure us somehow ;-)) which we keep until the next call.
// If there is a next call, then we first prepend the characters we kept from the previous call to the content inside the buffer (which might complete a chunked </body> tag for instance)
// and start our check all over again (which might result in finding a </body> tag or discarding a previously found </body> tag because that one was not the last one.
// Anyhow, as long as we are not a the end and a </body> tag has been found previously, the output will be buffered, just to make sure there is no other </body> tag further down the stream.
// If there is no next call, then the Flush method will be called and that one will deal with the current state, which means:
// - in case there was a </body> tag found, the replacement will be done
// - in case there was no </body> tag found, then the warning will be written to the log, indicating something went wrong
// either way, the remaining unwritten characters will be sent down the output stream.
string contentInBuffer = ContentEncoding.GetString(buffer, offset, count);
// Prepend remaining characters from the previous call, if any
if (!string.IsNullOrEmpty(UnwrittenCharactersFromPreviousCall))
{
contentInBuffer = UnwrittenCharactersFromPreviousCall + contentInBuffer;
UnwrittenCharactersFromPreviousCall = null;
}
Match closingBodyTagMatch = BodyEndRegex.Match(contentInBuffer);
if (closingBodyTagMatch.Success)
{
// Hooray, we found "a" </body> tag, but that doesn't mean that this is "the" last </body> tag we are looking for
// so we write everything before that match to the output stream
WriteToOutputStream(contentInBuffer.Substring(0, closingBodyTagMatch.Index));
// and keep the remainder for the next call or the Flush if there is no next call
UnwrittenCharactersFromPreviousCall = contentInBuffer.Substring(closingBodyTagMatch.Index);
}
else
{
// there is no match found for </body> which could have different reasons like case 2.2 for instance
// therefor we'll write everything except the last 10 characters to the output stream and we'll keep the last 10 characters for the next call or the Flush method
if (contentInBuffer.Length <= 10)
{
// the content has a maximum length of 10 characters, so we don't need to write anything to the output stream and we'll keep those
// characters for the next call (most likely the Flush)
UnwrittenCharactersFromPreviousCall = contentInBuffer;
}
else
{
WriteToOutputStream(contentInBuffer.Substring(0, contentInBuffer.Length - 10));
UnwrittenCharactersFromPreviousCall = contentInBuffer.Substring(contentInBuffer.Length - 10);
}
}
}