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pub use fastly_shared::CacheOverride;
use super::PendingRequest;
use crate::abi;
use crate::error::Error;
use crate::handle::{BodyHandle, ResponseHandle};
use crate::http::request::SendErrorCause;
use std::convert::TryInto;
/// A handle to a pending asynchronous request returned by
/// [`RequestHandle::send_async()`][`crate::handle::RequestHandle::send_async()`] or
/// [`RequestHandle::send_async_streaming()`][`crate::handle::RequestHandle::send_async_streaming()`].
///
/// A handle can be evaluated using [`PendingRequestHandle::poll()`],
/// [`PendingRequestHandle::wait()`], or [`select_handles()`][`crate::handle::select_handles()`]. It
/// can also be discarded if the request was sent for effects it might have, and the response is
/// unimportant.
#[derive(Debug, Eq, Hash, PartialEq)]
#[repr(transparent)]
pub struct PendingRequestHandle {
handle: u32,
}
impl From<PendingRequest> for PendingRequestHandle {
fn from(pr: PendingRequest) -> Self {
pr.handle
}
}
impl PendingRequestHandle {
pub(crate) const INVALID: Self = Self {
handle: fastly_shared::INVALID_PENDING_REQUEST_HANDLE,
};
pub(crate) fn is_invalid(&self) -> bool {
self == &Self::INVALID
}
/// Make a handle from its underlying representation.
///
/// This should only be used when calling the raw ABI directly, and care should be taken not to
/// reuse or alias handle values.
pub(crate) fn from_u32(handle: u32) -> Self {
Self { handle }
}
/// Get the underlying representation of the handle.
///
/// This should only be used when calling the raw ABI directly, and care should be taken not to
/// reuse or alias handle values.
pub(crate) fn as_u32(&self) -> u32 {
self.handle
}
/// Make a copy of the handle.
///
/// This should only be used when calling the raw ABI directly, and care should be taken not to
/// reuse or alias handle values.
pub(crate) fn copy(&self) -> Self {
Self {
handle: self.handle,
}
}
/// Get a mutable reference to the underlying `u32` representation of the handle.
///
/// This should only be used when calling the raw ABI directly, and care should be taken not to
/// reuse or alias handle values.
pub(crate) fn as_u32_mut(&mut self) -> &mut u32 {
&mut self.handle
}
/// Try to get the result of a pending request without blocking.
///
/// This function returns immediately with a [`PollHandleResult`]; if you want to block until a
/// result is ready, use [`wait()`][`Self::wait()`].
pub fn poll(self) -> PollHandleResult {
let mut is_done = -1;
let mut resp_handle = ResponseHandle::INVALID;
let mut body_handle = BodyHandle::INVALID;
let status = unsafe {
abi::fastly_http_req::pending_req_poll(
self.as_u32(),
&mut is_done,
resp_handle.as_u32_mut(),
body_handle.as_u32_mut(),
)
};
// An error indicates either that a handle was invalid or that a request did get polled and
// had some error for us. For example, we could begin receiving a response that gets
// truncated early; we might poll it ready with an Incomplete status.
if status.is_err() {
return PollHandleResult::Done(Err(SendErrorCause::status(status)));
}
if is_done < 0 || is_done > 1 {
// For witx reasons, is_done is indicated by a 0 or 1, rather than a "boolean" type.
// Getting an out of range value here should be impossible.
panic!("fastly_http_req_pending_req_poll internal error");
}
let is_done = if is_done == 0 { false } else { true };
if !is_done {
return PollHandleResult::Pending(self);
}
if is_done && (resp_handle.is_invalid() || body_handle.is_invalid()) {
PollHandleResult::Done(Err(SendErrorCause::Generic(Error::msg(
"asynchronous request failed",
))))
} else {
PollHandleResult::Done(Ok((resp_handle, body_handle)))
}
}
/// Block until the result of a pending request is ready.
///
/// If you want check whether the result is ready without blocking, use
/// [`poll()`][`Self::poll()`].
pub fn wait(self) -> Result<(ResponseHandle, BodyHandle), SendErrorCause> {
let mut resp_handle = ResponseHandle::INVALID;
let mut body_handle = BodyHandle::INVALID;
let status = unsafe {
abi::fastly_http_req::pending_req_wait(
self.as_u32(),
resp_handle.as_u32_mut(),
body_handle.as_u32_mut(),
)
};
if status.is_err() {
return Err(SendErrorCause::status(status));
}
if resp_handle.is_invalid() || body_handle.is_invalid() {
panic!("fastly_http_req::pending_req_wait returned invalid handles");
}
Ok((resp_handle, body_handle))
}
}
/// The result of a call to [`PendingRequestHandle::poll()`].
pub enum PollHandleResult {
/// The request is still in progress, and can be polled again using the given handle.
Pending(PendingRequestHandle),
/// The request has either completed or errored.
Done(Result<(ResponseHandle, BodyHandle), SendErrorCause>),
}
/// Given a collection of [`PendingRequestHandle`]s, block until the result of one of the handles is
/// ready.
///
/// This function accepts any type which can become an iterator that yields handles; a common choice
/// is `Vec<PendingRequestHandle>`.
///
/// Returns a tuple `(result, index, remaining)`, where:
///
/// - `result` is the result of the handle that became ready.
///
/// - `index` is the index of the handle in the argument collection (e.g., the index of the handle
/// in a vector) that became ready.
///
/// - `remaining` is a vector containing all of the handles that did not become ready. The order of
/// the handles in this vector is not guaranteed to match the order of the handles in the argument
/// collection.
///
/// ### Panics
///
/// Panics if the argument collection is empty, or contains more than
/// [`fastly_shared::MAX_PENDING_REQS`] handles.
pub fn select_handles<I>(
pending_reqs: I,
) -> (
Result<(ResponseHandle, BodyHandle), SendErrorCause>,
usize,
Vec<PendingRequestHandle>,
)
where
I: IntoIterator<Item = PendingRequestHandle>,
{
let mut prs = pending_reqs
.into_iter()
.map(|pr| pr.as_u32())
.collect::<Vec<u32>>();
if prs.is_empty() || prs.len() > fastly_shared::MAX_PENDING_REQS as usize {
panic!(
"the number of selected handles must be at least 1, and less than {}",
fastly_shared::MAX_PENDING_REQS
);
}
let mut done_index = -1;
let mut resp_handle = ResponseHandle::INVALID;
let mut body_handle = BodyHandle::INVALID;
let status = unsafe {
abi::fastly_http_req::pending_req_select(
prs.as_ptr(),
prs.len(),
&mut done_index,
resp_handle.as_u32_mut(),
body_handle.as_u32_mut(),
)
};
if status.is_err() || done_index < 0 {
// since we are providing the out-pointers, and an owned `PendingRequestHandle` in Wasm can
// only exist if it's present in the host, any error returns from the hostcall would
// indicate an internal (host) bug. Alternatively, the provided set of handles is empty or
// beyond MAX_PENDING_REQS, and we want to panic here anyway.
panic!("fastly_http_req_pending_req_select internal error");
}
// If we successfully (status is not an error) waited for a handle, we must have gotten
// something for a handle we provided. This means `done_index` must be valid.
let done_index = done_index
.try_into()
.expect("fastly_http_req_pending_req_select returned an invalid index");
// quickly remove the completed handle from the set to return
prs.swap_remove(done_index);
let res = if resp_handle.is_invalid() || body_handle.is_invalid() {
// HACK: work around an ABI limitation: for the time being we can't return a FastlyStatus
// error *and* provide out-parameters. We lose the specific error cause, but we still know
// from the invalid handle that `done_index` is the failed request.
Err(SendErrorCause::Generic(Error::msg(
"selected request failed",
)))
} else {
Ok((resp_handle, body_handle))
};
(
res,
done_index,
prs.into_iter()
.map(PendingRequestHandle::from_u32)
.collect(),
)
}