The Tor Browser: ipc/glue/SharedMemory.h@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-

     2  * vim: sw=2 ts=8 et :

     3  */

     4 /* This Source Code Form is subject to the terms of the Mozilla Public

     5  * License, v. 2.0. If a copy of the MPL was not distributed with this

     6  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     8 #ifndef mozilla_ipc_SharedMemory_h

     9 #define mozilla_ipc_SharedMemory_h

    11 #include "nsDebug.h"

    12 #include "nsISupportsImpl.h"    // NS_INLINE_DECL_REFCOUNTING

    13 #include "mozilla/Attributes.h"

    15 //

    16 // This is a low-level wrapper around platform shared memory.  Don't

    17 // use it directly; use Shmem allocated through IPDL interfaces.

    18 //

    19 namespace {

    20 enum Rights {

    21   RightsNone = 0,

    22   RightsRead = 1 << 0,

    23   RightsWrite = 1 << 1

    24 };

    25 }

    27 namespace mozilla {

    28 namespace ipc {

    30 class SharedMemory

    31 {

    32 public:

    33   virtual ~SharedMemory()

    34   {

    35     MOZ_COUNT_DTOR(SharedMemory);

    36     Unmapped();

    37     Destroyed();

    38   }

    40   enum SharedMemoryType {

    41     TYPE_BASIC,

    42     TYPE_SYSV,

    43     TYPE_UNKNOWN

    44   };

    46   size_t Size() const { return mMappedSize; }

    48   virtual void* memory() const = 0;

    50   virtual bool Create(size_t size) = 0;

    51   virtual bool Map(size_t nBytes) = 0;

    53   virtual SharedMemoryType Type() const = 0;

    55   void

    56   Protect(char* aAddr, size_t aSize, int aRights)

    57   {

    58     char* memStart = reinterpret_cast<char*>(memory());

    59     if (!memStart)

    60       NS_RUNTIMEABORT("SharedMemory region points at NULL!");

    61     char* memEnd = memStart + Size();

    63     char* protStart = aAddr;

    64     if (!protStart)

    65       NS_RUNTIMEABORT("trying to Protect() a NULL region!");

    66     char* protEnd = protStart + aSize;

    68     if (!(memStart <= protStart

    69           && protEnd <= memEnd))

    70       NS_RUNTIMEABORT("attempt to Protect() a region outside this SharedMemory");

    72     // checks alignment etc.

    73     SystemProtect(aAddr, aSize, aRights);

    74   }

    76   NS_INLINE_DECL_REFCOUNTING(SharedMemory)

    78   static void SystemProtect(char* aAddr, size_t aSize, int aRights);

    79   static size_t SystemPageSize();

    80   static size_t PageAlignedSize(size_t aSize);

    82 protected:

    83   SharedMemory();

    85   // Implementations should call these methods on shmem usage changes,

    86   // but *only if* the OS-specific calls are known to have succeeded.

    87   // The methods are expected to be called in the pattern

    88   //

    89   //   Created (Mapped Unmapped)* Destroy

    90   //

    91   // but this isn't checked.

    92   void Created(size_t aNBytes);

    93   void Mapped(size_t aNBytes);

    94   void Unmapped();

    95   void Destroyed();

    97   // The size of the shmem region requested in Create(), if

    98   // successful.  SharedMemory instances that are opened from a

    99   // foreign handle have an alloc size of 0, even though they have

   100   // access to the alloc-size information.

   101   size_t mAllocSize;

   102   // The size of the region mapped in Map(), if successful.  All

   103   // SharedMemorys that are mapped have a non-zero mapped size.

   104   size_t mMappedSize;

   105 };

   107 } // namespace ipc

   108 } // namespace mozilla

   111 #endif // ifndef mozilla_ipc_SharedMemory_h

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