I've been working on implementing a solid HTTP library in Rust, currently at http://github.com/chris-morgan/rust-http. Servo has been using Joyent's HTTP parser and this is a problem that I had observed with it. Yes, it is pretty badly implemented, but it's not a mess because of the style of code—that's for performance. It's only a mess because it's inconsistent and incorrect.

Reading the HTTP method in a high-performance way does lead to superficially ugly code. That's why code generation is good. Ragel has been mentioned and I intend to seriously consider using it, but for the moment my own HTTP method reading code is generated with:

    generate_branchified_method(
        writer,
        branchify!(case sensitive,
            "CONNECT" => Connect,
            "DELETE"  => Delete,
            "GET"     => Get,
            "HEAD"    => Head,
            "OPTIONS" => Options,
            "PATCH"   => Patch,
            "POST"    => Post,
            "PUT"     => Put,
            "TRACE"   => Trace
        ),
        1,
        "self.stream.read_byte()",
        "SP",
        "MAX_METHOD_LEN",
        "is_token_item(b)",
        "ExtensionMethod(%s)");

This is pleasantly easy to read and meaningful.

This generates the high performance artwork shown at http://sprunge.us/HdTH, which supports extension methods correctly. (Rust's algebraic data types are marvellous for many things in implementing such a spec.)