Trailers can be parsed by invoking the function using something along the lines of ParseHttpMessage((struct HttpMessage){.t = kHttpStateName}, p, n) where you just tell the parser to skip the first-line states. Charset isn't a nightmare either. Headers are ISO-8601-1 so you just say {0300 | c >> 6, 0200 | c & 077} to turn them into UTF-8. It's not difficult. It might be if you want to support MIME. But this is HTTP we're talking about. It was made to be simple! We're talking Internet engineering on the lowest difficulty setting. Implement a TCP or SIP stack if you want hard.
I think ysleepy might be referring to HTML charsets, which can be set in the HTTP header. They are a nightmare, I have come across HTML documents with so many “if lt IE 9” comments that they move the charset declaration out of the first 1000 bytes, causing browsers to ignore it and interpret as Latin 1. But yes, not actually anything to do with parsing HTTP.
