gecko-dev/dom/ipc/MemMapSnapshot.h

65 строки
1.7 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=99: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef dom_ipc_MemMapSnapshot_h
#define dom_ipc_MemMapSnapshot_h
#include "mozilla/AutoMemMap.h"
#include "mozilla/Attributes.h"
#include "mozilla/Maybe.h"
#include "mozilla/RangedPtr.h"
#include "mozilla/Result.h"
#ifdef XP_WIN
# include "mozilla/ipc/FileDescriptor.h"
#endif
namespace mozilla {
namespace ipc {
/**
* A helper class for creating a read-only snapshot of memory-mapped data.
*
* The Init() method initializes a read-write memory mapped region of the given
* size, which can be initialized with arbitrary data. The Finalize() method
* remaps that region as read-only (and backs it with a read-only file
* descriptor), and initializes an AutoMemMap with the new contents.
*
* The file descriptor for the resulting AutoMemMap can be shared among
* processes, to safely access a shared, read-only copy of the data snapshot.
*/
class MOZ_RAII MemMapSnapshot
{
public:
Result<Ok, nsresult> Init(size_t aSize);
Result<Ok, nsresult> Finalize(loader::AutoMemMap& aMap);
template<typename T = void>
RangedPtr<T> Get()
{
MOZ_ASSERT(mInitialized);
return mMem.get<T>();
}
private:
Result<Ok, nsresult> Create(size_t aSize);
Result<Ok, nsresult> Freeze(loader::AutoMemMap& aMem);
loader::AutoMemMap mMem;
bool mInitialized = false;
#ifdef XP_WIN
Maybe<FileDescriptor> mFile;
#else
nsCString mPath;
#endif
};
} // ipc
} // mozilla
#endif // dom_ipc_MemMapSnapshot_h