From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 21:33:14 +0200 Subject: Adding upstream version 115.7.0esr. Signed-off-by: Daniel Baumann --- ipc/chromium/src/base/waitable_event.h | 173 +++++++++++++++++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 ipc/chromium/src/base/waitable_event.h (limited to 'ipc/chromium/src/base/waitable_event.h') diff --git a/ipc/chromium/src/base/waitable_event.h b/ipc/chromium/src/base/waitable_event.h new file mode 100644 index 0000000000..40ed103b01 --- /dev/null +++ b/ipc/chromium/src/base/waitable_event.h @@ -0,0 +1,173 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#ifndef BASE_WAITABLE_EVENT_H_ +#define BASE_WAITABLE_EVENT_H_ + +#include "base/basictypes.h" + +#if defined(OS_WIN) +# include +#endif + +#if defined(OS_POSIX) +# include +# include +# include "base/condition_variable.h" +# include "base/lock.h" +# include "nsISupportsImpl.h" +#endif + +#include "base/message_loop.h" + +namespace base { + +// This replaces INFINITE from Win32 +static const int kNoTimeout = -1; + +class TimeDelta; + +// A WaitableEvent can be a useful thread synchronization tool when you want to +// allow one thread to wait for another thread to finish some work. For +// non-Windows systems, this can only be used from within a single address +// space. +// +// Use a WaitableEvent when you would otherwise use a Lock+ConditionVariable to +// protect a simple boolean value. However, if you find yourself using a +// WaitableEvent in conjunction with a Lock to wait for a more complex state +// change (e.g., for an item to be added to a queue), then you should probably +// be using a ConditionVariable instead of a WaitableEvent. +// +// NOTE: On Windows, this class provides a subset of the functionality afforded +// by a Windows event object. This is intentional. If you are writing Windows +// specific code and you need other features of a Windows event, then you might +// be better off just using an Windows event directly. +class WaitableEvent { + public: + // If manual_reset is true, then to set the event state to non-signaled, a + // consumer must call the Reset method. If this parameter is false, then the + // system automatically resets the event state to non-signaled after a single + // waiting thread has been released. + WaitableEvent(bool manual_reset, bool initially_signaled); + + ~WaitableEvent(); + + // Put the event in the un-signaled state. + void Reset(); + + // Put the event in the signaled state. Causing any thread blocked on Wait + // to be woken up. + void Signal(); + + // Returns true if the event is in the signaled state, else false. If this + // is not a manual reset event, then this test will cause a reset. + bool IsSignaled(); + + // Wait indefinitely for the event to be signaled. Returns true if the event + // was signaled, else false is returned to indicate that waiting failed. + bool Wait(); + + // Wait up until max_time has passed for the event to be signaled. Returns + // true if the event was signaled. If this method returns false, then it + // does not necessarily mean that max_time was exceeded. + bool TimedWait(const TimeDelta& max_time); + +#if defined(OS_WIN) + HANDLE handle() const { return handle_; } +#endif + + // Wait, synchronously, on multiple events. + // waitables: an array of WaitableEvent pointers + // count: the number of elements in @waitables + // + // returns: the index of a WaitableEvent which has been signaled. + // + // You MUST NOT delete any of the WaitableEvent objects while this wait is + // happening. + static size_t WaitMany(WaitableEvent** waitables, size_t count); + + // For asynchronous waiting, see WaitableEventWatcher + + // This is a private helper class. It's here because it's used by friends of + // this class (such as WaitableEventWatcher) to be able to enqueue elements + // of the wait-list + class Waiter { + public: + // Signal the waiter to wake up. + // + // Consider the case of a Waiter which is in multiple WaitableEvent's + // wait-lists. Each WaitableEvent is automatic-reset and two of them are + // signaled at the same time. Now, each will wake only the first waiter in + // the wake-list before resetting. However, if those two waiters happen to + // be the same object (as can happen if another thread didn't have a chance + // to dequeue the waiter from the other wait-list in time), two auto-resets + // will have happened, but only one waiter has been signaled! + // + // Because of this, a Waiter may "reject" a wake by returning false. In + // this case, the auto-reset WaitableEvent shouldn't act as if anything has + // been notified. + virtual bool Fire(WaitableEvent* signaling_event) = 0; + + // Waiters may implement this in order to provide an extra condition for + // two Waiters to be considered equal. In WaitableEvent::Dequeue, if the + // pointers match then this function is called as a final check. See the + // comments in ~Handle for why. + virtual bool Compare(void* tag) = 0; + }; + + private: + friend class WaitableEventWatcher; + +#if defined(OS_WIN) + HANDLE handle_; +#else + // On Windows, one can close a HANDLE which is currently being waited on. The + // MSDN documentation says that the resulting behaviour is 'undefined', but + // it doesn't crash. However, if we were to include the following members + // directly then, on POSIX, one couldn't use WaitableEventWatcher to watch an + // event which gets deleted. This mismatch has bitten us several times now, + // so we have a kernel of the WaitableEvent, which is reference counted. + // WaitableEventWatchers may then take a reference and thus match the Windows + // behaviour. + struct WaitableEventKernel final { + public: + NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WaitableEventKernel) + WaitableEventKernel(bool manual_reset, bool initially_signaled) + : manual_reset_(manual_reset), signaled_(initially_signaled) {} + + bool Dequeue(Waiter* waiter, void* tag); + + Lock lock_; + const bool manual_reset_; + bool signaled_; + std::list waiters_; + + protected: + ~WaitableEventKernel() {} + }; + + RefPtr kernel_; + + bool SignalAll(); + bool SignalOne(); + void Enqueue(Waiter* waiter); + + // When dealing with arrays of WaitableEvent*, we want to sort by the address + // of the WaitableEvent in order to have a globally consistent locking order. + // In that case we keep them, in sorted order, in an array of pairs where the + // second element is the index of the WaitableEvent in the original, + // unsorted, array. + typedef std::pair WaiterAndIndex; + static size_t EnqueueMany(WaiterAndIndex* waitables, size_t count, + Waiter* waiter); +#endif + + DISALLOW_COPY_AND_ASSIGN(WaitableEvent); +}; + +} // namespace base + +#endif // BASE_WAITABLE_EVENT_H_ -- cgit v1.2.3