Convert Future<Body> into Body #157
Description
Hi,
This is a feature request to add a conversion Future<Output=Result<Body, E>> → Body<Error=E>.
http-body-util currently does not seem to provide a straightforward way to turn a Future<Body> into a Body. This is particularly useful when you create a Body through an asynchronous computation that you then send a body over a oneshot channel. The typical workaround is to use FutureExt::into_stream, StreamExt::flat_map and do map with Frame::data.
example implementation
pin_project! {
#[project = FutureBodyProj]
#[derive(Debug)]
pub enum FutureBody<F, B> {
Future{#[pin] future: F},
Body{#[pin] body: B},
}
}
impl<F, B> FutureBody<F, B> {
pub fn new(future: F) -> Self {
Self::Future { future }
}
}
impl<F: Future<Output = Result<B, B::Error>>, B: http_body::Body> http_body::Body
for FutureBody<F, B>
{
type Data = B::Data;
type Error = B::Error;
fn poll_frame(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Result<http_body::Frame<Self::Data>, Self::Error>>> {
loop {
match self.as_mut().project() {
FutureBodyProj::Future { future } => {
let body = match ready!(future.poll(cx)) {
Ok(x) => x,
Err(err) => return Poll::Ready(Some(Err(err))),
};
self.set(FutureBody::Body { body });
}
FutureBodyProj::Body { body } => {
return body.poll_frame(cx);
}
}
}
}
fn is_end_stream(&self) -> bool {
match self {
FutureBody::Future { .. } => false,
FutureBody::Body { body } => body.is_end_stream(),
}
}
fn size_hint(&self) -> http_body::SizeHint {
match self {
FutureBody::Future { .. } => http_body::SizeHint::new(),
FutureBody::Body { body } => body.size_hint(),
}
}
}