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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
#ifndef mozilla_dom_ipc_StructuredCloneData_h
#define mozilla_dom_ipc_StructuredCloneData_h
#include <algorithm>
#include "mozilla/RefPtr.h"
#include "mozilla/dom/StructuredCloneHolder.h"
#include "nsISupportsImpl.h"
#include "nsIInputStream.h"
namespace IPC {
class Message;
class MessageReader;
class MessageWriter;
} // namespace IPC
class PickleIterator;
namespace mozilla {
namespace ipc {
class PBackgroundChild;
class PBackgroundParent;
} // namespace ipc
namespace dom {
class ContentChild;
class ContentParent;
namespace ipc {
/**
* Wraps the non-reference-counted JSStructuredCloneData class to have a
* reference count so that multiple StructuredCloneData instances can reference
* a single underlying serialized representation.
*
* As used by StructuredCloneData, it is an invariant that our
* JSStructuredCloneData owns its buffers. (For the non-owning case,
* StructuredCloneData uses mExternalData which holds a BufferList::Borrow()ed
* read-only view of the data.)
*/
class SharedJSAllocatedData final {
public:
explicit SharedJSAllocatedData(JSStructuredCloneData&& aData)
: mData(std::move(aData)) {}
static already_AddRefed<SharedJSAllocatedData> CreateFromExternalData(
const char* aData, size_t aDataLength) {
JSStructuredCloneData buf(JS::StructuredCloneScope::DifferentProcess);
NS_ENSURE_TRUE(buf.AppendBytes(aData, aDataLength), nullptr);
RefPtr<SharedJSAllocatedData> sharedData =
new SharedJSAllocatedData(std::move(buf));
return sharedData.forget();
}
static already_AddRefed<SharedJSAllocatedData> CreateFromExternalData(
const JSStructuredCloneData& aData) {
JSStructuredCloneData buf(aData.scope());
NS_ENSURE_TRUE(buf.Append(aData), nullptr);
RefPtr<SharedJSAllocatedData> sharedData =
new SharedJSAllocatedData(std::move(buf));
return sharedData.forget();
}
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedJSAllocatedData)
JSStructuredCloneData& Data() { return mData; }
size_t DataLength() const { return mData.Size(); }
private:
~SharedJSAllocatedData() = default;
JSStructuredCloneData mData;
};
/**
* IPC-aware StructuredCloneHolder subclass that serves as both a helper class
* for dealing with message data (blobs, transferables) and also an IPDL
* data-type in cases where message data is not needed. If your use-case does
* not (potentially) involve IPC, then you should use StructuredCloneHolder or
* one of its other subclasses instead.
*
* ## Usage ##
*
* The general recipe for using this class is:
* - In your IPDL definition, use the ClonedMessageData type whenever you want
* to send a structured clone that may include blobs or transferables such as
* message ports.
* - To send the data, instantiate a StructuredCloneData instance and Write()
* into it like a normal structured clone. When you are ready to send the
* ClonedMessageData-bearing IPC message, call the BuildClonedMessageData
* method to populate the ClonedMessageData and then send it before your
* StructuredCloneData instance is destroyed. (Buffer borrowing is used
* under-the-hood to avoid duplicating the serialized data, requiring this.)
* - To receive the data, instantiate a StructuredCloneData and then call
* the BorrowFromClonedMessageData method. See the memory management
* section for more information.
*
* ## Memory Management ##
*
* Serialized structured clone representations can be quite large. So it's best
* to avoid wasteful duplication. When Write()ing into the StructuredCloneData,
* you don't need to worry about this[1], but when you already have serialized
* structured clone data you plan to Read(), you do need to. Similarly, if
* you're using StructuredCloneData as an IPDL type, it efficiently unmarshals.
*
* The from-ClonedMessageData memory management strategies available are:
* - Borrow: Create a JSStructuredCloneData that holds a non-owning, read-only
* BufferList::Borrow()ed copy of the source. Your StructuredCloneData needs
* to be destroyed before the source is. Commonly used when the
* StructuredCloneData instance is stack-allocated (and Read() is used before
* the function returns).
* - Copy: Makes a reference-counted copy of the source JSStructuredCloneData,
* making it safe for the StructuredCloneData to outlive the source data.
* - Steal: Steal the buffers from the underlying JSStructuredCloneData so that
* it's safe for the StructuredCloneData to outlive the source data. This is
* safe to use with IPC-provided ClonedMessageData instances because
* JSStructuredCloneData's IPC ParamTraits::Read method copies the relevant
* data into owned buffers. But if it's possible the ClonedMessageData came
* from a different source that might have borrowed the buffers itself, then
* things will crash. That would be a pretty strange implementation; if you
* see one, change it to use SharedJSAllocatedData.
*
* 1: Specifically, in the Write() case an owning SharedJSAllocatedData is
* created efficiently (by stealing from StructuredCloneHolder). The
* BuildClonedMessageData method can be called at any time and it will
* borrow the underlying memory. While it would be even better if
* SerializedStructuredCloneBuffer could hold a SharedJSAllocatedData ref,
* there's no reason you can't wait to call the BuildClonedMessageData
* method until you need to make the IPC Send* call.
*/
class StructuredCloneData : public StructuredCloneHolder {
public:
StructuredCloneData();
StructuredCloneData(const StructuredCloneData&) = delete;
StructuredCloneData(StructuredCloneData&& aOther);
// Only DifferentProcess and UnknownDestination scopes are supported.
StructuredCloneData(StructuredCloneScope aScope,
TransferringSupport aSupportsTransferring);
~StructuredCloneData();
StructuredCloneData& operator=(const StructuredCloneData& aOther) = delete;
StructuredCloneData& operator=(StructuredCloneData&& aOther);
const nsTArray<RefPtr<BlobImpl>>& BlobImpls() const { return mBlobImplArray; }
nsTArray<RefPtr<BlobImpl>>& BlobImpls() { return mBlobImplArray; }
const nsTArray<nsCOMPtr<nsIInputStream>>& InputStreams() const {
return mInputStreamArray;
}
nsTArray<nsCOMPtr<nsIInputStream>>& InputStreams() {
return mInputStreamArray;
}
bool Copy(const StructuredCloneData& aData);
void Read(JSContext* aCx, JS::MutableHandle<JS::Value> aValue,
ErrorResult& aRv);
void Read(JSContext* aCx, JS::MutableHandle<JS::Value> aValue,
const JS::CloneDataPolicy& aCloneDataPolicy, ErrorResult& aRv);
// Write with no transfer objects and with the default CloneDataPolicy. With
// a default CloneDataPolicy, read and write will not be considered as part of
// the same agent cluster and shared memory objects will not be supported.
void Write(JSContext* aCx, JS::Handle<JS::Value> aValue,
ErrorResult& aRv) override;
// The most generic Write method, with tansfers and CloneDataPolicy.
void Write(JSContext* aCx, JS::Handle<JS::Value> aValue,
JS::Handle<JS::Value> aTransfers,
const JS::CloneDataPolicy& aCloneDataPolicy,
ErrorResult& aRv) override;
// Method to convert the structured clone stored in this holder by a previous
// call to Write() into ClonedMessageData IPC representation.
bool BuildClonedMessageData(ClonedMessageData& aClonedData);
// Memory-management-strategy-varying methods to initialize this holder from a
// ClonedMessageData representation.
void BorrowFromClonedMessageData(const ClonedMessageData& aClonedData);
void CopyFromClonedMessageData(const ClonedMessageData& aClonedData);
// The steal variant of course takes a non-const ClonedMessageData.
void StealFromClonedMessageData(ClonedMessageData& aClonedData);
// Initialize this instance, borrowing the contents of the given
// JSStructuredCloneData. You are responsible for ensuring that this
// StructuredCloneData instance is destroyed before aData is destroyed.
bool UseExternalData(const JSStructuredCloneData& aData) {
auto iter = aData.Start();
bool success = false;
mExternalData = aData.Borrow(iter, aData.Size(), &success);
mInitialized = true;
return success;
}
// Initialize this instance by copying the given data that probably came from
// nsStructuredClone doing a base64 decode. Don't use this.
bool CopyExternalData(const char* aData, size_t aDataLength);
// Initialize this instance by copying the contents of an existing
// JSStructuredCloneData. Use when this StructuredCloneData instance may
// outlive aData.
bool CopyExternalData(const JSStructuredCloneData& aData);
// Initialize this instance by stealing the contents of aData via Move
// constructor, clearing the original aData as a side-effect. This is only
// safe if aData owns the underlying buffers. This is the case for instances
// provided by IPC to Recv calls.
bool StealExternalData(JSStructuredCloneData& aData);
JSStructuredCloneData& Data() {
return mSharedData ? mSharedData->Data() : mExternalData;
}
const JSStructuredCloneData& Data() const {
return mSharedData ? mSharedData->Data() : mExternalData;
}
void InitScope(JS::StructuredCloneScope aScope) { Data().initScope(aScope); }
size_t DataLength() const {
return mSharedData ? mSharedData->DataLength() : mExternalData.Size();
}
SharedJSAllocatedData* SharedData() const { return mSharedData; }
bool SupportsTransferring() { return mSupportsTransferring; }
// For IPC serialization
void WriteIPCParams(IPC::MessageWriter* aWriter) const;
bool ReadIPCParams(IPC::MessageReader* aReader);
protected:
already_AddRefed<SharedJSAllocatedData> TakeSharedData();
private:
JSStructuredCloneData mExternalData;
RefPtr<SharedJSAllocatedData> mSharedData;
bool mInitialized;
};
} // namespace ipc
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_ipc_StructuredCloneData_h