1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/threads/nsEventQueue.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,92 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim:set ts=2 sw=2 sts=2 et cindent: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef nsEventQueue_h__
1.11 +#define nsEventQueue_h__
1.12 +
1.13 +#include <stdlib.h>
1.14 +#include "mozilla/ReentrantMonitor.h"
1.15 +#include "nsIRunnable.h"
1.16 +
1.17 +// A threadsafe FIFO event queue...
1.18 +class nsEventQueue
1.19 +{
1.20 + typedef mozilla::ReentrantMonitor ReentrantMonitor;
1.21 +
1.22 +public:
1.23 + nsEventQueue();
1.24 + ~nsEventQueue();
1.25 +
1.26 + // This method adds a new event to the pending event queue. The event object
1.27 + // is AddRef'd if this method succeeds. This method returns true if the
1.28 + // event was stored in the event queue, and it returns false if it could
1.29 + // not allocate sufficient memory.
1.30 + bool PutEvent(nsIRunnable *event);
1.31 +
1.32 + // This method gets an event from the event queue. If mayWait is true, then
1.33 + // the method will block the calling thread until an event is available. If
1.34 + // the event is null, then the method returns immediately indicating whether
1.35 + // or not an event is pending. When the resulting event is non-null, the
1.36 + // caller is responsible for releasing the event object. This method does
1.37 + // not alter the reference count of the resulting event.
1.38 + bool GetEvent(bool mayWait, nsIRunnable **event);
1.39 +
1.40 + // This method returns true if there is a pending event.
1.41 + bool HasPendingEvent() {
1.42 + return GetEvent(false, nullptr);
1.43 + }
1.44 +
1.45 + // This method returns the next pending event or null.
1.46 + bool GetPendingEvent(nsIRunnable **runnable) {
1.47 + return GetEvent(false, runnable);
1.48 + }
1.49 +
1.50 + // This method waits for and returns the next pending event.
1.51 + bool WaitPendingEvent(nsIRunnable **runnable) {
1.52 + return GetEvent(true, runnable);
1.53 + }
1.54 +
1.55 + // Expose the event queue's monitor for "power users"
1.56 + ReentrantMonitor& GetReentrantMonitor() {
1.57 + return mReentrantMonitor;
1.58 + }
1.59 +
1.60 +private:
1.61 +
1.62 + bool IsEmpty() {
1.63 + return !mHead || (mHead == mTail && mOffsetHead == mOffsetTail);
1.64 + }
1.65 +
1.66 + enum { EVENTS_PER_PAGE = 255 };
1.67 +
1.68 + // Page objects are linked together to form a simple deque.
1.69 +
1.70 + struct Page {
1.71 + struct Page *mNext;
1.72 + nsIRunnable *mEvents[EVENTS_PER_PAGE];
1.73 + };
1.74 +
1.75 + static_assert((sizeof(Page) & (sizeof(Page) - 1)) == 0,
1.76 + "sizeof(Page) should be a power of two to avoid heap slop.");
1.77 +
1.78 + static Page *NewPage() {
1.79 + return static_cast<Page *>(calloc(1, sizeof(Page)));
1.80 + }
1.81 +
1.82 + static void FreePage(Page *p) {
1.83 + free(p);
1.84 + }
1.85 +
1.86 + ReentrantMonitor mReentrantMonitor;
1.87 +
1.88 + Page *mHead;
1.89 + Page *mTail;
1.90 +
1.91 + uint16_t mOffsetHead; // offset into mHead where next item is removed
1.92 + uint16_t mOffsetTail; // offset into mTail where next item is added
1.93 +};
1.94 +
1.95 +#endif // nsEventQueue_h__
