Based on the apparently unmaintained mime crate

mime

Support MIME (HTTP Media Types) as strong types in Rust.

Documentation

Usage

extern crate mime;

fn main() {
    // common types are constants
    let text = mime::TEXT_PLAIN;

    // deconstruct Mimes to match on them
    match (text.type_(), text.subtype()) {
        (mime::TEXT, mime::PLAIN) => {
            // plain text!
        },
        (mime::TEXT, _) => {
            // structured text!
        },
        _ => {
            // not text!
        }
    }
}