This dedicated `Entity` trait replaces the previous `Stream<Item=impl
AsRef<[u8]>, Error=hyper::Error>`. This allows for several improvements
immediately, and prepares for HTTP2 support.
- The `Entity::is_end_stream` makes up for change away from
`Option<Body>`, which was previously used to know if the body should be
empty. Since `Request` and `Response` now require a body to be set,
this method can be used to tell hyper that the body is actually empty.
It also provides the possibility of slight optimizations when polling
for data, by allowing to check `is_end_stream` before polling again.
This can allow a consumer to know that a body stream has ended without
polling for `None` afterwards.
- The `Entity::content_length` method allows a body to automatically
declare a size, in case a user doesn't set a `Content-Length` or
`Transfer-Encoding` header.
- It's now possible to send and receive trailers, though this will be
for HTTP2 connections only.
By being a trait owned by hyper, new methods can be added later as new
features are wanted (with default implementations).
The `hyper::Body` type now implements `Entity` instead of `Stream`,
provides a better channel option, and is easier to use with custom
streams via `Body::wrap_stream`.
BREAKING CHANGE: All code that was assuming the body was a `Stream` must
be adjusted to use an `Entity` instead.
Using `hyper::Body` as a `Stream` can call `Body::into_stream`
to get a stream wrapper.
Passing a custom `impl Stream` will need to either implement
`Entity`, or as an easier option, switch to `Body::wrap_stream`.
`Body::pair` has been replaced with `Body::channel`, which returns a
`hyper::body::Sender` instead of a `futures::sync::mpsc::Sender`.
Closes#1438
fbc449e49c