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Side by Side Diff: mojo/edk/system/waiter.h

Issue 814543006: Move //mojo/{public, edk} underneath //third_party (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Rebase Created 5 years, 11 months ago
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1 // Copyright 2013 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_EDK_SYSTEM_WAITER_H_
6 #define MOJO_EDK_SYSTEM_WAITER_H_
7
8 #include <stdint.h>
9
10 #include "base/macros.h"
11 #include "base/synchronization/condition_variable.h"
12 #include "base/synchronization/lock.h"
13 #include "mojo/edk/system/awakable.h"
14 #include "mojo/edk/system/system_impl_export.h"
15 #include "mojo/public/c/system/types.h"
16
17 namespace mojo {
18 namespace system {
19
20 // IMPORTANT (all-caps gets your attention, right?): |Waiter| methods are called
21 // under other locks, in particular, |Dispatcher::lock_|s, so |Waiter| methods
22 // must never call out to other objects (in particular, |Dispatcher|s). This
23 // class is thread-safe.
24 class MOJO_SYSTEM_IMPL_EXPORT Waiter : public Awakable {
25 public:
26 Waiter();
27 ~Waiter();
28
29 // A |Waiter| can be used multiple times; |Init()| should be called before
30 // each time it's used.
31 void Init();
32
33 // Waits until a suitable |Awake()| is called. (|context| may be null, in
34 // which case, obviously no context is ever returned.)
35 // Returns:
36 // - The result given to the first call to |Awake()| (possibly before this
37 // call to |Wait()|); in this case, |*context| is set to the value passed
38 // to that call to |Awake()|.
39 // - |MOJO_RESULT_DEADLINE_EXCEEDED| if the deadline was exceeded; in this
40 // case |*context| is not modified.
41 //
42 // Usually, the context passed to |Awake()| will be the value passed to
43 // |Dispatcher::AddAwakable()|, which is usually the index to the array of
44 // handles passed to |MojoWaitMany()| (or 0 for |MojoWait()|).
45 //
46 // Typical |Awake()| results are:
47 // - |MOJO_RESULT_OK| if one of the flags passed to
48 // |MojoWait()|/|MojoWaitMany()| (hence |Dispatcher::AddAwakable()|) was
49 // satisfied;
50 // - |MOJO_RESULT_CANCELLED| if a handle (on which
51 // |MojoWait()|/|MojoWaitMany()| was called) was closed (hence the
52 // dispatcher closed); and
53 // - |MOJO_RESULT_FAILED_PRECONDITION| if one of the set of flags passed to
54 // |MojoWait()|/|MojoWaitMany()| cannot or can no longer be satisfied by
55 // the corresponding handle (e.g., if the other end of a message or data
56 // pipe is closed).
57 MojoResult Wait(MojoDeadline deadline, uint32_t* context);
58
59 // Wake the waiter up with the given result and context (or no-op if it's been
60 // woken up already).
61 bool Awake(MojoResult result, uintptr_t context) override;
62
63 private:
64 base::ConditionVariable cv_; // Associated to |lock_|.
65 base::Lock lock_; // Protects the following members.
66 #ifndef NDEBUG
67 bool initialized_;
68 #endif
69 bool awoken_;
70 MojoResult awake_result_;
71 uintptr_t awake_context_;
72
73 DISALLOW_COPY_AND_ASSIGN(Waiter);
74 };
75
76 } // namespace system
77 } // namespace mojo
78
79 #endif // MOJO_EDK_SYSTEM_WAITER_H_
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