The Tor Browser / file comparison
comparison: xpcom/threads/nsEventQueue.h
xpcom/threads/nsEventQueue.h
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:1ea962680771 |
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| 1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* vim:set ts=2 sw=2 sts=2 et cindent: */ | |
| 3 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 #ifndef nsEventQueue_h__ | |
| 8 #define nsEventQueue_h__ | |
| 9 | |
| 10 #include <stdlib.h> | |
| 11 #include "mozilla/ReentrantMonitor.h" | |
| 12 #include "nsIRunnable.h" | |
| 13 | |
| 14 // A threadsafe FIFO event queue... | |
| 15 class nsEventQueue | |
| 16 { | |
| 17 typedef mozilla::ReentrantMonitor ReentrantMonitor; | |
| 18 | |
| 19 public: | |
| 20 nsEventQueue(); | |
| 21 ~nsEventQueue(); | |
| 22 | |
| 23 // This method adds a new event to the pending event queue. The event object | |
| 24 // is AddRef'd if this method succeeds. This method returns true if the | |
| 25 // event was stored in the event queue, and it returns false if it could | |
| 26 // not allocate sufficient memory. | |
| 27 bool PutEvent(nsIRunnable *event); | |
| 28 | |
| 29 // This method gets an event from the event queue. If mayWait is true, then | |
| 30 // the method will block the calling thread until an event is available. If | |
| 31 // the event is null, then the method returns immediately indicating whether | |
| 32 // or not an event is pending. When the resulting event is non-null, the | |
| 33 // caller is responsible for releasing the event object. This method does | |
| 34 // not alter the reference count of the resulting event. | |
| 35 bool GetEvent(bool mayWait, nsIRunnable **event); | |
| 36 | |
| 37 // This method returns true if there is a pending event. | |
| 38 bool HasPendingEvent() { | |
| 39 return GetEvent(false, nullptr); | |
| 40 } | |
| 41 | |
| 42 // This method returns the next pending event or null. | |
| 43 bool GetPendingEvent(nsIRunnable **runnable) { | |
| 44 return GetEvent(false, runnable); | |
| 45 } | |
| 46 | |
| 47 // This method waits for and returns the next pending event. | |
| 48 bool WaitPendingEvent(nsIRunnable **runnable) { | |
| 49 return GetEvent(true, runnable); | |
| 50 } | |
| 51 | |
| 52 // Expose the event queue's monitor for "power users" | |
| 53 ReentrantMonitor& GetReentrantMonitor() { | |
| 54 return mReentrantMonitor; | |
| 55 } | |
| 56 | |
| 57 private: | |
| 58 | |
| 59 bool IsEmpty() { | |
| 60 return !mHead || (mHead == mTail && mOffsetHead == mOffsetTail); | |
| 61 } | |
| 62 | |
| 63 enum { EVENTS_PER_PAGE = 255 }; | |
| 64 | |
| 65 // Page objects are linked together to form a simple deque. | |
| 66 | |
| 67 struct Page { | |
| 68 struct Page *mNext; | |
| 69 nsIRunnable *mEvents[EVENTS_PER_PAGE]; | |
| 70 }; | |
| 71 | |
| 72 static_assert((sizeof(Page) & (sizeof(Page) - 1)) == 0, | |
| 73 "sizeof(Page) should be a power of two to avoid heap slop."); | |
| 74 | |
| 75 static Page *NewPage() { | |
| 76 return static_cast<Page *>(calloc(1, sizeof(Page))); | |
| 77 } | |
| 78 | |
| 79 static void FreePage(Page *p) { | |
| 80 free(p); | |
| 81 } | |
| 82 | |
| 83 ReentrantMonitor mReentrantMonitor; | |
| 84 | |
| 85 Page *mHead; | |
| 86 Page *mTail; | |
| 87 | |
| 88 uint16_t mOffsetHead; // offset into mHead where next item is removed | |
| 89 uint16_t mOffsetTail; // offset into mTail where next item is added | |
| 90 }; | |
| 91 | |
| 92 #endif // nsEventQueue_h__ |
