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CrossProcessSemaphore.h (3179B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      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 mozilla_CrossProcessSemaphore_h
      8 #define mozilla_CrossProcessSemaphore_h
      9 
     10 #include "base/process.h"
     11 #include "mozilla/TimeStamp.h"
     12 #include "mozilla/Maybe.h"
     13 
     14 #if defined(XP_WIN) || defined(XP_DARWIN)
     15 #  include "mozilla/UniquePtrExtensions.h"
     16 #else
     17 #  include <pthread.h>
     18 #  include <semaphore.h>
     19 #  include "mozilla/ipc/SharedMemoryMapping.h"
     20 #  include "mozilla/Atomics.h"
     21 #endif
     22 
     23 namespace IPC {
     24 template <typename T>
     25 struct ParamTraits;
     26 }  // namespace IPC
     27 
     28 //
     29 // Provides:
     30 //
     31 //  - CrossProcessSemaphore, a semaphore that can be shared across processes
     32 namespace mozilla {
     33 
     34 template <typename T>
     35 inline bool IsHandleValid(const T& handle) {
     36  return bool(handle);
     37 }
     38 
     39 #if defined(XP_WIN)
     40 typedef mozilla::UniqueFileHandle CrossProcessSemaphoreHandle;
     41 #elif defined(XP_DARWIN)
     42 typedef mozilla::UniqueMachSendRight CrossProcessSemaphoreHandle;
     43 #else
     44 typedef mozilla::ipc::MutableSharedMemoryHandle CrossProcessSemaphoreHandle;
     45 #endif
     46 
     47 class CrossProcessSemaphore {
     48 public:
     49  /**
     50   * CrossProcessSemaphore
     51   * @param name A name which can reference this lock (currently unused)
     52   **/
     53  static CrossProcessSemaphore* Create(const char* aName,
     54                                       uint32_t aInitialValue);
     55 
     56  /**
     57   * CrossProcessSemaphore
     58   * @param handle A handle of an existing cross process semaphore that can be
     59   *               opened.
     60   */
     61  static CrossProcessSemaphore* Create(CrossProcessSemaphoreHandle aHandle);
     62 
     63  ~CrossProcessSemaphore();
     64 
     65  /**
     66   * Decrements the current value of the semaphore. This will block if the
     67   * current value of the semaphore is 0, up to a maximum of aWaitTime (if
     68   * specified).
     69   * Returns true if the semaphore was succesfully decremented, false otherwise.
     70   **/
     71  bool Wait(const Maybe<TimeDuration>& aWaitTime = Nothing());
     72 
     73  /**
     74   * Increments the current value of the semaphore.
     75   **/
     76  void Signal();
     77 
     78  /**
     79   * CloneHandle
     80   * This function is called to generate a serializable structure that can
     81   * be sent to the specified process and opened on the other side.
     82   *
     83   * @returns A handle that can be shared to another process
     84   */
     85  CrossProcessSemaphoreHandle CloneHandle();
     86 
     87  void CloseHandle();
     88 
     89 private:
     90  friend struct IPC::ParamTraits<CrossProcessSemaphore>;
     91 
     92  CrossProcessSemaphore();
     93  CrossProcessSemaphore(const CrossProcessSemaphore&);
     94  CrossProcessSemaphore& operator=(const CrossProcessSemaphore&);
     95 
     96 #if defined(XP_WIN)
     97  explicit CrossProcessSemaphore(HANDLE aSemaphore);
     98 
     99  HANDLE mSemaphore;
    100 #elif defined(XP_DARWIN)
    101  explicit CrossProcessSemaphore(CrossProcessSemaphoreHandle aSemaphore);
    102 
    103  CrossProcessSemaphoreHandle mSemaphore;
    104 #else
    105  mozilla::ipc::MutableSharedMemoryHandle mHandle;
    106  mozilla::ipc::SharedMemoryMapping mSharedBuffer;
    107  sem_t* mSemaphore;
    108  mozilla::Atomic<int32_t>* mRefCount;
    109 #endif
    110 };
    111 
    112 }  // namespace mozilla
    113 
    114 #endif