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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 xpcselfhostedshmem_h___
#define xpcselfhostedshmem_h___
#include "base/shared_memory.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/UniquePtrExtensions.h"
#include "mozilla/Span.h"
#include "mozilla/StaticPtr.h"
#include "nsIMemoryReporter.h"
#include "nsIObserver.h"
#include "nsIThread.h"
namespace xpc {
// This class is a singleton which holds a file-mapping of the Self Hosted
// Stencil XDR, to be shared by the parent process with all the child processes.
//
// It is either initialized by the parent process by monitoring when the Self
// hosted stencil is produced, or by the content process by reading a shared
// memory-mapped file.
class SelfHostedShmem final : public nsIMemoryReporter {
public:
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSIMEMORYREPORTER
// NOTE: This type is identical to JS::SelfHostedCache, but we repeat it to
// avoid including JS engine API in ipc code.
using ContentType = mozilla::Span<const uint8_t>;
static SelfHostedShmem& GetSingleton();
// Initialize this singleton with the content of the Self-hosted Stencil XDR.
// This will be used to initialize the shared memory which would hold a copy.
//
// This function is not thread-safe and should be call at most once and from
// the main thread.
void InitFromParent(ContentType aXdr);
// Initialize this singleton with the content coming from the parent process,
// using a file handle which maps to the memory pages of the parent process.
//
// This function is not thread-safe and should be call at most once and from
// the main thread.
[[nodiscard]] bool InitFromChild(base::SharedMemoryHandle aHandle,
size_t aLen);
// Return a span over the read-only XDR content of the self-hosted stencil.
ContentType Content() const;
// Return the file handle which is under which the content is mapped.
const mozilla::UniqueFileHandle& Handle() const;
// Register this class to the memory reporter service.
void InitMemoryReporter();
// Unregister this class from the memory reporter service, and delete the
// memory associated with the shared memory. As the memory is borrowed by the
// JS engine, this function should be called after JS_Shutdown.
//
// NOTE: This is not using the Observer service which would call Shutdown
// while JS code might still be running during shutdown process.
static void Shutdown();
private:
SelfHostedShmem() = default;
~SelfHostedShmem() = default;
static mozilla::StaticRefPtr<SelfHostedShmem> sSelfHostedXdr;
// read-only file Handle used to transfer from the parent process to content
// processes.
mozilla::UniqueFileHandle mHandle;
// Shared memory used by JS runtime initialization.
mozilla::UniquePtr<base::SharedMemory> mMem;
// Length of the content within the shared memory.
size_t mLen = 0;
};
} // namespace xpc
#endif // !xpcselfhostedshmem_h___
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