1 files changed, 117 insertions, 0 deletions
diff --git a/xpcom/base/StaticMonitor.h b/xpcom/base/StaticMonitor.h
new file mode 100644
index 0000000000..b35d3871d2
--- /dev/null
+++ b/xpcom/base/StaticMonitor.h
@@ -0,0 +1,117 @@
+/* -*- 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