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54 lines
1.6 KiB
C++
54 lines
1.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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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 dom_ipc_MemMapSnapshot_h
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#define dom_ipc_MemMapSnapshot_h
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#include "mozilla/Attributes.h"
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#include "mozilla/Maybe.h"
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#include "mozilla/RangedPtr.h"
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#include "mozilla/Result.h"
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#include "base/shared_memory.h"
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#include "ErrorList.h"
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namespace mozilla {
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namespace loader {
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class AutoMemMap;
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}
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namespace ipc {
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/**
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* A helper class for creating a read-only snapshot of memory-mapped data.
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*
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* The Init() method initializes a read-write memory mapped region of the given
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* size, which can be initialized with arbitrary data. The Finalize() method
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* remaps that region as read-only (and backs it with a read-only file
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* descriptor), and initializes an AutoMemMap with the new contents.
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*
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* The file descriptor for the resulting AutoMemMap can be shared among
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* processes, to safely access a shared, read-only copy of the data snapshot.
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*/
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class MOZ_RAII MemMapSnapshot {
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public:
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Result<Ok, nsresult> Init(size_t aSize);
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Result<Ok, nsresult> Finalize(loader::AutoMemMap& aMap);
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template <typename T>
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RangedPtr<T> Get() {
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MOZ_ASSERT(mInitialized);
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return {static_cast<T*>(mMem.memory()), mMem.max_size() / sizeof(T)};
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}
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private:
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base::SharedMemory mMem;
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bool mInitialized = false;
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};
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} // namespace ipc
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} // namespace mozilla
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#endif // dom_ipc_MemMapSnapshot_h
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