118 lines
3.1 KiB
C++
118 lines
3.1 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* vim: sw=2 ts=8 et :
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*/
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_ipc_SharedMemory_h
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#define mozilla_ipc_SharedMemory_h
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#include "nsDebug.h"
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#include "nsISupportsImpl.h" // NS_INLINE_DECL_REFCOUNTING
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#include "mozilla/Attributes.h"
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//
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// This is a low-level wrapper around platform shared memory. Don't
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// use it directly; use Shmem allocated through IPDL interfaces.
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//
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namespace {
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enum Rights {
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RightsNone = 0,
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RightsRead = 1 << 0,
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RightsWrite = 1 << 1
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};
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} // namespace
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namespace mozilla {
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namespace ipc {
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class SharedMemory;
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} // namespace ipc
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namespace ipc {
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class SharedMemory
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{
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protected:
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virtual ~SharedMemory()
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{
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Unmapped();
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Destroyed();
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}
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public:
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enum SharedMemoryType {
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TYPE_BASIC,
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TYPE_SYSV,
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TYPE_UNKNOWN
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};
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size_t Size() const { return mMappedSize; }
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virtual void* memory() const = 0;
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virtual bool Create(size_t size) = 0;
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virtual bool Map(size_t nBytes) = 0;
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virtual SharedMemoryType Type() const = 0;
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void
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Protect(char* aAddr, size_t aSize, int aRights)
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{
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char* memStart = reinterpret_cast<char*>(memory());
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if (!memStart)
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NS_RUNTIMEABORT("SharedMemory region points at NULL!");
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char* memEnd = memStart + Size();
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char* protStart = aAddr;
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if (!protStart)
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NS_RUNTIMEABORT("trying to Protect() a NULL region!");
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char* protEnd = protStart + aSize;
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if (!(memStart <= protStart
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&& protEnd <= memEnd))
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NS_RUNTIMEABORT("attempt to Protect() a region outside this SharedMemory");
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// checks alignment etc.
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SystemProtect(aAddr, aSize, aRights);
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}
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// bug 1168843, compositor thread may create shared memory instances that are destroyed by main thread on shutdown, so this must use thread-safe RC to avoid hitting assertion
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NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedMemory)
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static void SystemProtect(char* aAddr, size_t aSize, int aRights);
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static size_t SystemPageSize();
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static size_t PageAlignedSize(size_t aSize);
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protected:
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SharedMemory();
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// Implementations should call these methods on shmem usage changes,
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// but *only if* the OS-specific calls are known to have succeeded.
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// The methods are expected to be called in the pattern
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//
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// Created (Mapped Unmapped)* Destroy
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//
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// but this isn't checked.
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void Created(size_t aNBytes);
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void Mapped(size_t aNBytes);
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void Unmapped();
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void Destroyed();
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// The size of the shmem region requested in Create(), if
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// successful. SharedMemory instances that are opened from a
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// foreign handle have an alloc size of 0, even though they have
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// access to the alloc-size information.
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size_t mAllocSize;
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// The size of the region mapped in Map(), if successful. All
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// SharedMemorys that are mapped have a non-zero mapped size.
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size_t mMappedSize;
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};
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} // namespace ipc
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} // namespace mozilla
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#endif // ifndef mozilla_ipc_SharedMemory_h
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