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// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library zx;
@transport("Syscall")
protocol Eventpair {
/// ## Summary
///
/// Create an event pair.
///
/// ## Declaration
///
/// ```c
/// #include <zircon/syscalls.h>
///
/// zx_status_t zx_eventpair_create(uint32_t options,
/// zx_handle_t* out0,
/// zx_handle_t* out1);
/// ```
///
/// ## Description
///
/// `zx_eventpair_create()` creates an event pair, which is a pair of objects that
/// are mutually signalable.
///
/// The signals **ZX_EVENTPAIR_SIGNALED** and **ZX_USER_SIGNAL_n** (where *n* is 0 through 7)
/// may be set or cleared using [`zx_object_signal()`], which modifies the signals on the
/// object itself, or [`zx_object_signal_peer()`], which modifies the signals on its
/// counterpart.
///
/// When all the handles to one of the objects have been closed, the
/// **ZX_EVENTPAIR_PEER_CLOSED** signal will be asserted on the opposing object.
///
/// The newly-created handles will have the **ZX_RIGHT_TRANSFER**,
/// **ZX_RIGHT_DUPLICATE**, **ZX_RIGHT_READ**, **ZX_RIGHT_WRITE**, **ZX_RIGHT_SIGNAL**,
/// and **ZX_RIGHT_SIGNAL_PEER** rights.
///
/// Currently, no options are supported, so *options* must be set to 0.
///
/// ## Rights
///
/// Caller job policy must allow **ZX_POL_NEW_EVENTPAIR**.
///
/// ## Return value
///
/// `zx_eventpair_create()` returns **ZX_OK** on success. On failure, a (negative)
/// error code is returned.
///
/// ## Errors
///
/// **ZX_ERR_INVALID_ARGS** *out0* or *out1* is an invalid pointer or NULL.
///
/// **ZX_ERR_NOT_SUPPORTED** *options* has an unsupported flag set (i.e., is not 0).
///
/// **ZX_ERR_NO_MEMORY** Failure due to lack of memory.
/// There is no good way for userspace to handle this (unlikely) error.
/// In a future build this error will no longer occur.
///
/// ## See also
///
/// - [`zx_event_create()`]
/// - [`zx_handle_close()`]
/// - [`zx_handle_duplicate()`]
/// - [`zx_handle_replace()`]
/// - [`zx_object_signal()`]
/// - [`zx_object_signal_peer()`]
/// - [`zx_object_wait_async()`]
/// - [`zx_object_wait_many()`]
/// - [`zx_object_wait_one()`]
///
/// [`zx_event_create()`]: event_create.md
/// [`zx_handle_close()`]: handle_close.md
/// [`zx_handle_duplicate()`]: handle_duplicate.md
/// [`zx_handle_replace()`]: handle_replace.md
/// [`zx_object_signal()`]: object_signal.md
/// [`zx_object_signal_peer()`]: object_signal_peer.md
/// [`zx_object_wait_async()`]: object_wait_async.md
/// [`zx_object_wait_many()`]: object_wait_many.md
/// [`zx_object_wait_one()`]: object_wait_one.md
Create(struct {
options uint32;
}) -> (resource struct {
out0 handle:EVENT;
out1 handle:EVENT;
}) error status;
};