Discuss the implementation of textdecoder serialize function

text decode serialize

fn serialize(mut self, stream: &[u8]) -> &[u8] {
        match self.encoding.name() {
            "utf-8" | "utf-16be" | "utf-16le" if (!self.ignoreBOM && !self.BOMseen) => {
                match stream.get(0) {
                    Some(token) => {
                        self.BOMseen = true;
                        if *token == 0xFEFF {
                            stream.slice_from(1)
                        } else {
                            stream
                        }
                    },
                    None => stream
                }
            },
            _ => stream
        }
    }
}