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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #ifndef MOJO_PUBLIC_C_ENVIRONMENT_ASYNC_WAITER_H_ | |
| 6 #define MOJO_PUBLIC_C_ENVIRONMENT_ASYNC_WAITER_H_ | |
| 7 | |
| 8 #include "mojo/public/c/system/types.h" | |
| 9 | |
| 10 typedef uintptr_t MojoAsyncWaitID; | |
| 11 | |
| 12 typedef void (*MojoAsyncWaitCallback)(void* closure, MojoResult result); | |
| 13 | |
| 14 // Functions for asynchronously waiting (and cancelling asynchronous waits) on a | |
| 15 // handle. | |
| 16 // | |
| 17 // Thread-safety: | |
| 18 // - |CancelWait(wait_id)| may only be called on the same thread as the | |
| 19 // |AsyncWait()| that provided |wait_id| was called on. | |
| 20 // - A given |MojoAsyncWaiter|'s functions may only be called on the thread(s) | |
| 21 // that it is defined to be valid on (typically including the thread on | |
| 22 // which the |MojoAsyncWaiter| was provided). E.g., a library may require | |
| 23 // initialization with a single |MojoAsyncWaiter| and stipulate that it only | |
| 24 // be used on threads on which that |MojoAsyncWaiter| is valid. | |
| 25 // - If a |MojoAsyncWaiter| is valid on multiple threads, then its functions | |
| 26 // must be thread-safe (subject to the first restriction above). | |
| 27 struct MojoAsyncWaiter { | |
| 28 // Arranges for |callback| to be called on the current thread at some future | |
| 29 // when |handle| satisfies |signals| or it is known that it will never satisfy | |
| 30 // |signals| (with the same behavior as |MojoWait()|). | |
| 31 // | |
| 32 // |callback| will not be called in the nested context of |AsyncWait()|, but | |
| 33 // only, e.g., from some run loop. |callback| is provided with the |closure| | |
| 34 // argument as well as the result of the wait. For each call to |AsyncWait()|, | |
| 35 // |callback| will be called at most once. | |
| 36 // | |
| 37 // |handle| must not be closed or transferred (via |MojoWriteMessage()|; this | |
| 38 // is equivalent to closing the handle) until either the callback has been | |
| 39 // executed or the async wait has been cancelled using the returned (nonzero) | |
| 40 // |MojoAsyncWaitID| (see |CancelWait()|). Otherwise, an invalid (or, worse, | |
| 41 // re-used) handle may be waited on by the implementation of this | |
| 42 // |MojoAsyncWaiter|. | |
| 43 // | |
| 44 // Note that once the callback has been called, the returned |MojoAsyncWaitID| | |
| 45 // becomes invalid. | |
| 46 MojoAsyncWaitID (*AsyncWait)(MojoHandle handle, | |
| 47 MojoHandleSignals signals, | |
| 48 MojoDeadline deadline, | |
| 49 MojoAsyncWaitCallback callback, | |
| 50 void* closure); | |
| 51 | |
| 52 // Cancels an outstanding async wait (specified by |wait_id|) initiated by | |
| 53 // |AsyncWait()|. This may only be called from the same thread on which the | |
| 54 // corresponding |AsyncWait()| was called, and may only be called if the | |
| 55 // callback to |AsyncWait()| has not been called. | |
| 56 // | |
| 57 // Once this has been called, the callback provided to |AsyncWait()| will not | |
| 58 // be called. Moreover, it is then immediately safe to close or transfer the | |
| 59 // handle provided to |AsyncWait()|. (I.e., the implementation of this | |
| 60 // |MojoAsyncWaiter| will no longer wait on, or do anything else with, the | |
| 61 // handle.) | |
| 62 void (*CancelWait)(MojoAsyncWaitID wait_id); | |
| 63 }; | |
| 64 | |
| 65 #endif // MOJO_PUBLIC_C_ENVIRONMENT_ASYNC_WAITER_H_ | |
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