michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "nsMemoryPressure.h"
michael@0: #include "mozilla/Assertions.h"
michael@0: #include "mozilla/Atomics.h"
michael@0: 
michael@0: #include "nsThreadUtils.h"
michael@0: 
michael@0: using namespace mozilla;
michael@0: 
michael@0: static Atomic<int32_t, Relaxed> sMemoryPressurePending;
michael@0: static_assert(MemPressure_None == 0,
michael@0:               "Bad static initialization with the default constructor.");
michael@0: 
michael@0: MemoryPressureState
michael@0: NS_GetPendingMemoryPressure()
michael@0: {
michael@0:   int32_t value = sMemoryPressurePending.exchange(MemPressure_None);
michael@0:   return MemoryPressureState(value);
michael@0: }
michael@0: 
michael@0: void
michael@0: NS_DispatchEventualMemoryPressure(MemoryPressureState state)
michael@0: {
michael@0:   /*
michael@0:    * A new memory pressure event erases an ongoing memory pressure, but an
michael@0:    * existing "new" memory pressure event takes precedence over a new "ongoing"
michael@0:    * memory pressure event.
michael@0:    */
michael@0:   switch (state) {
michael@0:     case MemPressure_None:
michael@0:       sMemoryPressurePending = MemPressure_None;
michael@0:       break;
michael@0:     case MemPressure_New:
michael@0:       sMemoryPressurePending = MemPressure_New;
michael@0:       break;
michael@0:     case MemPressure_Ongoing:
michael@0:       sMemoryPressurePending.compareExchange(MemPressure_None, MemPressure_Ongoing);
michael@0:       break;
michael@0:   }
michael@0: }
michael@0: 
michael@0: nsresult
michael@0: NS_DispatchMemoryPressure(MemoryPressureState state)
michael@0: {
michael@0:   NS_DispatchEventualMemoryPressure(state);
michael@0:   nsCOMPtr<nsIRunnable> event = new nsRunnable;
michael@0:   return NS_DispatchToMainThread(event);
michael@0: }