tmp/tmpxe7o0_6d/{from.md → to.md}
RENAMED
|
@@ -0,0 +1,83 @@
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1 |
+
## Receivers <a id="exec.recv">[[exec.recv]]</a>
|
| 2 |
+
|
| 3 |
+
### Receiver concepts <a id="exec.recv.concepts">[[exec.recv.concepts]]</a>
|
| 4 |
+
|
| 5 |
+
A receiver represents the continuation of an asynchronous operation. The
|
| 6 |
+
`receiver` concept defines the requirements for a receiver type
|
| 7 |
+
[[exec.async.ops]]. The `receiver_of` concept defines the requirements
|
| 8 |
+
for a receiver type that is usable as the first argument of a set of
|
| 9 |
+
completion operations corresponding to a set of completion signatures.
|
| 10 |
+
The `get_env` customization point object is used to access a receiver’s
|
| 11 |
+
associated environment.
|
| 12 |
+
|
| 13 |
+
``` cpp
|
| 14 |
+
namespace std::execution {
|
| 15 |
+
template<class Rcvr>
|
| 16 |
+
concept receiver =
|
| 17 |
+
derived_from<typename remove_cvref_t<Rcvr>::receiver_concept, receiver_t> &&
|
| 18 |
+
requires(const remove_cvref_t<Rcvr>& rcvr) {
|
| 19 |
+
{ get_env(rcvr) } -> queryable;
|
| 20 |
+
} &&
|
| 21 |
+
move_constructible<remove_cvref_t<Rcvr>> && // rvalues are movable, and
|
| 22 |
+
constructible_from<remove_cvref_t<Rcvr>, Rcvr>; // lvalues are copyable
|
| 23 |
+
|
| 24 |
+
template<class Signature, class Rcvr>
|
| 25 |
+
concept valid-completion-for = // exposition only
|
| 26 |
+
requires (Signature* sig) {
|
| 27 |
+
[]<class Tag, class... Args>(Tag(*)(Args...))
|
| 28 |
+
requires callable<Tag, remove_cvref_t<Rcvr>, Args...>
|
| 29 |
+
{}(sig);
|
| 30 |
+
};
|
| 31 |
+
|
| 32 |
+
template<class Rcvr, class Completions>
|
| 33 |
+
concept has-completions = // exposition only
|
| 34 |
+
requires (Completions* completions) {
|
| 35 |
+
[]<valid-completion-for<Rcvr>...Sigs>(completion_signatures<Sigs...>*)
|
| 36 |
+
{}(completions);
|
| 37 |
+
};
|
| 38 |
+
|
| 39 |
+
template<class Rcvr, class Completions>
|
| 40 |
+
concept receiver_of =
|
| 41 |
+
receiver<Rcvr> && has-completions<Rcvr, Completions>;
|
| 42 |
+
}
|
| 43 |
+
```
|
| 44 |
+
|
| 45 |
+
Class types that are marked `final` do not model the `receiver` concept.
|
| 46 |
+
|
| 47 |
+
Let `rcvr` be a receiver and let `op_state` be an operation state
|
| 48 |
+
associated with an asynchronous operation created by connecting `rcvr`
|
| 49 |
+
with a sender. Let `token` be a stop token equal to
|
| 50 |
+
`get_stop_token(get_env(rcvr))`. `token` shall remain valid for the
|
| 51 |
+
duration of the asynchronous operation’s lifetime [[exec.async.ops]].
|
| 52 |
+
|
| 53 |
+
[*Note 1*: This means that, unless it knows about further guarantees
|
| 54 |
+
provided by the type of `rcvr`, the implementation of `op_state` cannot
|
| 55 |
+
use `token` after it executes a completion operation. This also implies
|
| 56 |
+
that any stop callbacks registered on token must be destroyed before the
|
| 57 |
+
invocation of the completion operation. — *end note*]
|
| 58 |
+
|
| 59 |
+
### `execution::set_value` <a id="exec.set.value">[[exec.set.value]]</a>
|
| 60 |
+
|
| 61 |
+
`set_value` is a value completion function [[exec.async.ops]]. Its
|
| 62 |
+
associated completion tag is `set_value_t`. The expression
|
| 63 |
+
`set_value(rcvr, vs...)` for a subexpression `rcvr` and pack of
|
| 64 |
+
subexpressions `vs` is ill-formed if `rcvr` is an lvalue or an rvalue of
|
| 65 |
+
const type. Otherwise, it is expression-equivalent to
|
| 66 |
+
`MANDATE-NOTHROW(rcvr.set_value(vs...))`.
|
| 67 |
+
|
| 68 |
+
### `execution::set_error` <a id="exec.set.error">[[exec.set.error]]</a>
|
| 69 |
+
|
| 70 |
+
`set_error` is an error completion function [[exec.async.ops]]. Its
|
| 71 |
+
associated completion tag is `set_error_t`. The expression
|
| 72 |
+
`set_error(rcvr, err)` for some subexpressions `rcvr` and `err` is
|
| 73 |
+
ill-formed if `rcvr` is an lvalue or an rvalue of const type. Otherwise,
|
| 74 |
+
it is expression-equivalent to `MANDATE-NOTHROW(rcvr.set_error(err))`.
|
| 75 |
+
|
| 76 |
+
### `execution::set_stopped` <a id="exec.set.stopped">[[exec.set.stopped]]</a>
|
| 77 |
+
|
| 78 |
+
`set_stopped` is a stopped completion function [[exec.async.ops]]. Its
|
| 79 |
+
associated completion tag is `set_stopped_t`. The expression
|
| 80 |
+
`set_stopped(rcvr)` for a subexpression `rcvr` is ill-formed if `rcvr`
|
| 81 |
+
is an lvalue or an rvalue of const type. Otherwise, it is
|
| 82 |
+
expression-equivalent to `MANDATE-NOTHROW(rcvr.set_stopped())`.
|
| 83 |
+
|