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-rw-r--r--xpcom/base/StaticMonitor.h117
1 files changed, 117 insertions, 0 deletions
diff --git a/xpcom/base/StaticMonitor.h b/xpcom/base/StaticMonitor.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_StaticMonitor_h
+#define mozilla_StaticMonitor_h
+
+#include "mozilla/Atomics.h"
+#include "mozilla/CondVar.h"
+#include "mozilla/ThreadSafety.h"
+
+namespace mozilla {
+
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS MOZ_CAPABILITY("monitor")
+ StaticMonitor {
+ public:
+ // In debug builds, check that mMutex is initialized for us as we expect by
+ // the compiler. In non-debug builds, don't declare a constructor so that
+ // the compiler can see that the constructor is trivial.
+#ifdef DEBUG
+ StaticMonitor() { MOZ_ASSERT(!mMutex); }
+#endif
+
+ void Lock() MOZ_CAPABILITY_ACQUIRE() { Mutex()->Lock(); }
+
+ void Unlock() MOZ_CAPABILITY_RELEASE() { Mutex()->Unlock(); }
+
+ void Wait() { CondVar()->Wait(); }
+ CVStatus Wait(TimeDuration aDuration) {
+ AssertCurrentThreadOwns();
+ return CondVar()->Wait(aDuration);
+ }
+
+ void Notify() { CondVar()->Notify(); }
+ void NotifyAll() { CondVar()->NotifyAll(); }
+
+ void AssertCurrentThreadOwns() MOZ_ASSERT_CAPABILITY(this) {
+#ifdef DEBUG
+ Mutex()->AssertCurrentThreadOwns();
+#endif
+ }
+
+ private:
+ OffTheBooksMutex* Mutex() {
+ if (mMutex) {
+ return mMutex;
+ }
+
+ OffTheBooksMutex* mutex = new OffTheBooksMutex("StaticMutex");
+ if (!mMutex.compareExchange(nullptr, mutex)) {
+ delete mutex;
+ }
+
+ return mMutex;
+ }
+
+ OffTheBooksCondVar* CondVar() {
+ if (mCondVar) {
+ return mCondVar;
+ }
+
+ OffTheBooksCondVar* condvar =
+ new OffTheBooksCondVar(*Mutex(), "StaticCondVar");
+ if (!mCondVar.compareExchange(nullptr, condvar)) {
+ delete condvar;
+ }
+
+ return mCondVar;
+ }
+
+ Atomic<OffTheBooksMutex*> mMutex;
+ Atomic<OffTheBooksCondVar*> mCondVar;
+
+ // Disallow copy constructor, but only in debug mode. We only define
+ // a default constructor in debug mode (see above); if we declared
+ // this constructor always, the compiler wouldn't generate a trivial
+ // default constructor for us in non-debug mode.
+#ifdef DEBUG
+ StaticMonitor(const StaticMonitor& aOther);
+#endif
+
+ // Disallow these operators.
+ StaticMonitor& operator=(const StaticMonitor& aRhs);
+ static void* operator new(size_t) noexcept(true);
+ static void operator delete(void*);
+};
+
+class MOZ_STACK_CLASS MOZ_SCOPED_CAPABILITY StaticMonitorAutoLock {
+ public:
+ explicit StaticMonitorAutoLock(StaticMonitor& aMonitor)
+ MOZ_CAPABILITY_ACQUIRE(aMonitor)
+ : mMonitor(&aMonitor) {
+ mMonitor->Lock();
+ }
+
+ ~StaticMonitorAutoLock() MOZ_CAPABILITY_RELEASE() { mMonitor->Unlock(); }
+
+ void Wait() { mMonitor->Wait(); }
+ CVStatus Wait(TimeDuration aDuration) { return mMonitor->Wait(aDuration); }
+
+ void Notify() { mMonitor->Notify(); }
+ void NotifyAll() { mMonitor->NotifyAll(); }
+
+ private:
+ StaticMonitorAutoLock();
+ StaticMonitorAutoLock(const StaticMonitorAutoLock&);
+ StaticMonitorAutoLock& operator=(const StaticMonitorAutoLock&);
+ static void* operator new(size_t) noexcept(true);
+
+ StaticMonitor* mMonitor;
+};
+
+} // namespace mozilla
+
+#endif