Enum Body 

pub enum Body {
    Full(Vec<u8>),
    Stream(Box<dyn FnOnce(&mut dyn Write) -> Result<()> + Send + 'static>),
}

A response body: either fully buffered, or streamed incrementally.

Streaming leans on the connection-per-request, Connection: close model: we omit Content-Length, write the headers, then hand the raw socket to a producer closure that flushes bytes over time. The client reads until the connection closes (a valid HTTP/1.1 framing). No chunked encoding, no async.

Variants

Full(Vec<u8>)

Stream(Box<dyn FnOnce(&mut dyn Write) -> Result<()> + Send + 'static>)