michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
michael@0:  * vim: sw=2 ts=8 et :
michael@0:  */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_ipc_SharedMemory_h
michael@0: #define mozilla_ipc_SharedMemory_h
michael@0: 
michael@0: #include "nsDebug.h"
michael@0: #include "nsISupportsImpl.h"    // NS_INLINE_DECL_REFCOUNTING
michael@0: #include "mozilla/Attributes.h"
michael@0: 
michael@0: //
michael@0: // This is a low-level wrapper around platform shared memory.  Don't
michael@0: // use it directly; use Shmem allocated through IPDL interfaces.
michael@0: //
michael@0: namespace {
michael@0: enum Rights {
michael@0:   RightsNone = 0,
michael@0:   RightsRead = 1 << 0,
michael@0:   RightsWrite = 1 << 1
michael@0: };
michael@0: }
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace ipc {
michael@0: 
michael@0: class SharedMemory
michael@0: {
michael@0: public:
michael@0:   virtual ~SharedMemory()
michael@0:   {
michael@0:     MOZ_COUNT_DTOR(SharedMemory);
michael@0:     Unmapped();
michael@0:     Destroyed();
michael@0:   }
michael@0: 
michael@0:   enum SharedMemoryType {
michael@0:     TYPE_BASIC,
michael@0:     TYPE_SYSV,
michael@0:     TYPE_UNKNOWN
michael@0:   };
michael@0: 
michael@0:   size_t Size() const { return mMappedSize; }
michael@0: 
michael@0:   virtual void* memory() const = 0;
michael@0: 
michael@0:   virtual bool Create(size_t size) = 0;
michael@0:   virtual bool Map(size_t nBytes) = 0;
michael@0: 
michael@0:   virtual SharedMemoryType Type() const = 0;
michael@0: 
michael@0:   void
michael@0:   Protect(char* aAddr, size_t aSize, int aRights)
michael@0:   {
michael@0:     char* memStart = reinterpret_cast<char*>(memory());
michael@0:     if (!memStart)
michael@0:       NS_RUNTIMEABORT("SharedMemory region points at NULL!");
michael@0:     char* memEnd = memStart + Size();
michael@0: 
michael@0:     char* protStart = aAddr;
michael@0:     if (!protStart)
michael@0:       NS_RUNTIMEABORT("trying to Protect() a NULL region!");
michael@0:     char* protEnd = protStart + aSize;
michael@0: 
michael@0:     if (!(memStart <= protStart
michael@0:           && protEnd <= memEnd))
michael@0:       NS_RUNTIMEABORT("attempt to Protect() a region outside this SharedMemory");
michael@0: 
michael@0:     // checks alignment etc.
michael@0:     SystemProtect(aAddr, aSize, aRights);
michael@0:   }
michael@0: 
michael@0:   NS_INLINE_DECL_REFCOUNTING(SharedMemory)
michael@0: 
michael@0:   static void SystemProtect(char* aAddr, size_t aSize, int aRights);
michael@0:   static size_t SystemPageSize();
michael@0:   static size_t PageAlignedSize(size_t aSize);
michael@0: 
michael@0: protected:
michael@0:   SharedMemory();
michael@0: 
michael@0:   // Implementations should call these methods on shmem usage changes,
michael@0:   // but *only if* the OS-specific calls are known to have succeeded.
michael@0:   // The methods are expected to be called in the pattern
michael@0:   //
michael@0:   //   Created (Mapped Unmapped)* Destroy
michael@0:   //
michael@0:   // but this isn't checked.
michael@0:   void Created(size_t aNBytes);
michael@0:   void Mapped(size_t aNBytes);
michael@0:   void Unmapped();
michael@0:   void Destroyed();
michael@0: 
michael@0:   // The size of the shmem region requested in Create(), if
michael@0:   // successful.  SharedMemory instances that are opened from a
michael@0:   // foreign handle have an alloc size of 0, even though they have
michael@0:   // access to the alloc-size information.
michael@0:   size_t mAllocSize;
michael@0:   // The size of the region mapped in Map(), if successful.  All
michael@0:   // SharedMemorys that are mapped have a non-zero mapped size.
michael@0:   size_t mMappedSize;
michael@0: };
michael@0: 
michael@0: } // namespace ipc
michael@0: } // namespace mozilla
michael@0: 
michael@0: 
michael@0: #endif // ifndef mozilla_ipc_SharedMemory_h