ipc/glue/CrossProcessSemaphore.h

   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(OS_WIN)
  15 #  include "mozilla/UniquePtrExtensions.h"
  16 #endif
  17 #if !defined(OS_WIN) && !defined(OS_MACOSX)
  18 #  include <pthread.h>
  19 #  include <semaphore.h>
  20 #  include "mozilla/ipc/SharedMemoryBasic.h"
  21 #  include "mozilla/Atomics.h"
  22 #endif
  23
  24 namespace IPC {
  25 template <typename T>
  26 struct ParamTraits;
  27 }  // namespace IPC
  28
  29 //
  30 // Provides:
  31 //
  32 //  - CrossProcessSemaphore, a semaphore that can be shared across processes
  33 namespace mozilla {
  34
  35 template <typename T>
  36 inline bool IsHandleValid(const T& handle) {
  37   return bool(handle);
  38 }
  39
  40 #if defined(OS_WIN)
  41 typedef mozilla::UniqueFileHandle CrossProcessSemaphoreHandle;
  42 #elif !defined(OS_MACOSX)
  43 typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessSemaphoreHandle;
  44
  45 template <>
  46 inline bool IsHandleValid<CrossProcessSemaphoreHandle>(
  47     const CrossProcessSemaphoreHandle& handle) {
  48   return !(handle == mozilla::ipc::SharedMemoryBasic::NULLHandle());
  49 }
  50 #else
  51 // Stub for other platforms. We can't use uintptr_t here since different
  52 // processes could disagree on its size.
  53 typedef uintptr_t CrossProcessSemaphoreHandle;
  54 #endif
  55
  56 class CrossProcessSemaphore {
  57  public:
  58   /**
  59    * CrossProcessSemaphore
  60    * @param name A name which can reference this lock (currently unused)
  61    **/
  62   static CrossProcessSemaphore* Create(const char* aName,
  63                                        uint32_t aInitialValue);
  64
  65   /**
  66    * CrossProcessSemaphore
  67    * @param handle A handle of an existing cross process semaphore that can be
  68    *               opened.
  69    */
  70   static CrossProcessSemaphore* Create(CrossProcessSemaphoreHandle aHandle);
  71
  72   ~CrossProcessSemaphore();
  73
  74   /**
  75    * Decrements the current value of the semaphore. This will block if the
  76    * current value of the semaphore is 0, up to a maximum of aWaitTime (if
  77    * specified).
  78    * Returns true if the semaphore was succesfully decremented, false otherwise.
  79    **/
  80   bool Wait(const Maybe<TimeDuration>& aWaitTime = Nothing());
  81
  82   /**
  83    * Increments the current value of the semaphore.
  84    **/
  85   void Signal();
  86
  87   /**
  88    * CloneHandle
  89    * This function is called to generate a serializable structure that can
  90    * be sent to the specified process and opened on the other side.
  91    *
  92    * @returns A handle that can be shared to another process
  93    */
  94   CrossProcessSemaphoreHandle CloneHandle();
  95
  96   void CloseHandle();
  97
  98  private:
  99   friend struct IPC::ParamTraits<CrossProcessSemaphore>;
 100
 101   CrossProcessSemaphore();
 102   CrossProcessSemaphore(const CrossProcessSemaphore&);
 103   CrossProcessSemaphore& operator=(const CrossProcessSemaphore&);
 104
 105 #if defined(OS_WIN)
 106   explicit CrossProcessSemaphore(HANDLE aSemaphore);
 107
 108   HANDLE mSemaphore;
 109 #elif !defined(OS_MACOSX)
 110   RefPtr<mozilla::ipc::SharedMemoryBasic> mSharedBuffer;
 111   sem_t* mSemaphore;
 112   mozilla::Atomic<int32_t>* mRefCount;
 113 #endif
 114 };
 115
 116 }  // namespace mozilla
 117
 118 #endif