gecko/dom/base/StructuredCloneHelper.h

300 lines
9.4 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 mozilla_dom_StructuredCloneHelper_h
#define mozilla_dom_StructuredCloneHelper_h
#include "js/StructuredClone.h"
#include "nsAutoPtr.h"
#include "nsISupports.h"
#include "nsTArray.h"
#ifdef DEBUG
#include "nsIThread.h"
#endif
namespace mozilla {
class ErrorResult;
namespace layers {
class Image;
}
namespace dom {
class StructuredCloneHelperInternal
{
public:
StructuredCloneHelperInternal();
virtual ~StructuredCloneHelperInternal();
// These methods should be implemented in order to clone data.
// Read more documentation in js/public/StructuredClone.h.
virtual JSObject* ReadCallback(JSContext* aCx,
JSStructuredCloneReader* aReader,
uint32_t aTag,
uint32_t aIndex) = 0;
virtual bool WriteCallback(JSContext* aCx,
JSStructuredCloneWriter* aWriter,
JS::Handle<JSObject*> aObj) = 0;
// This method has to be called when this object is not needed anymore.
// It will free memory and the buffer. This has to be called because
// otherwise the buffer will be freed in the DTOR of this class and at that
// point we cannot use the overridden methods.
void Shutdown();
// If these 3 methods are not implement, transfering objects will not be
// allowed.
virtual bool
ReadTransferCallback(JSContext* aCx,
JSStructuredCloneReader* aReader,
uint32_t aTag,
void* aContent,
uint64_t aExtraData,
JS::MutableHandleObject aReturnObject);
virtual bool
WriteTransferCallback(JSContext* aCx,
JS::Handle<JSObject*> aObj,
// Output:
uint32_t* aTag,
JS::TransferableOwnership* aOwnership,
void** aContent,
uint64_t* aExtraData);
virtual void
FreeTransferCallback(uint32_t aTag,
JS::TransferableOwnership aOwnership,
void* aContent,
uint64_t aExtraData);
// These methods are what you should use.
bool Write(JSContext* aCx,
JS::Handle<JS::Value> aValue);
bool Write(JSContext* aCx,
JS::Handle<JS::Value> aValue,
JS::Handle<JS::Value> aTransfer);
bool Read(JSContext* aCx,
JS::MutableHandle<JS::Value> aValue);
bool HasBeenWritten() const
{
return !!mBuffer;
}
uint64_t* BufferData() const
{
MOZ_ASSERT(mBuffer, "Write() has never been called.");
return mBuffer->data();
}
size_t BufferSize() const
{
MOZ_ASSERT(mBuffer, "Write() has never been called.");
return mBuffer->nbytes();
}
protected:
nsAutoPtr<JSAutoStructuredCloneBuffer> mBuffer;
#ifdef DEBUG
bool mShutdownCalled;
#endif
};
class BlobImpl;
class MessagePortBase;
class MessagePortIdentifier;
class StructuredCloneHelper : public StructuredCloneHelperInternal
{
public:
enum CloningSupport
{
CloningSupported,
CloningNotSupported
};
enum TransferringSupport
{
TransferringSupported,
TransferringNotSupported
};
enum ContextSupport
{
SameProcessSameThread,
SameProcessDifferentThread,
DifferentProcess
};
// If cloning is supported, this object will clone objects such as Blobs,
// FileList, ImageData, etc.
// If transferring is supported, we will transfer MessagePorts and in the
// future other transferrable objects.
// The ContextSupport is useful to know where the cloned/transferred data can
// be read and written. Additional checks about the nature of the objects
// will be done based on this context value because not all the objects can
// be sent between threads or processes.
explicit StructuredCloneHelper(CloningSupport aSupportsCloning,
TransferringSupport aSupportsTransferring,
ContextSupport aContextSupport);
virtual ~StructuredCloneHelper();
// Normally you should just use Write() and Read().
void Write(JSContext* aCx,
JS::Handle<JS::Value> aValue,
ErrorResult &aRv);
void Write(JSContext* aCx,
JS::Handle<JS::Value> aValue,
JS::Handle<JS::Value> aTransfer,
ErrorResult &aRv);
void Read(nsISupports* aParent,
JSContext* aCx,
JS::MutableHandle<JS::Value> aValue,
ErrorResult &aRv);
// Sometimes, when IPC is involved, you must send a buffer after a Write().
// This method 'steals' the internal data from this helper class.
// You should free this buffer with FreeBuffer().
void MoveBufferDataToArray(FallibleTArray<uint8_t>& aArray,
ErrorResult& aRv);
bool HasClonedDOMObjects() const
{
return !mBlobImplArray.IsEmpty() ||
!mClonedImages.IsEmpty();
}
nsTArray<nsRefPtr<BlobImpl>>& BlobImpls()
{
MOZ_ASSERT(mSupportsCloning, "Blobs cannot be taken/set if cloning is not supported.");
return mBlobImplArray;
}
nsISupports* ParentDuringRead() const
{
return mParent;
}
// This must be called if the transferring has ports generated by Read().
// MessagePorts are not thread-safe and they must be retrieved in the thread
// where they are created.
void TakeTransferredPorts(nsTArray<nsRefPtr<MessagePortBase>>& aPorts)
{
MOZ_ASSERT(mSupportsTransferring);
MOZ_ASSERT(aPorts.IsEmpty());
aPorts.SwapElements(mTransferredPorts);
}
nsTArray<MessagePortIdentifier>& PortIdentifiers()
{
MOZ_ASSERT(mSupportsTransferring);
return mPortIdentifiers;
}
nsTArray<nsRefPtr<layers::Image>>& GetImages()
{
return mClonedImages;
}
// Custom Callbacks
virtual JSObject* ReadCallback(JSContext* aCx,
JSStructuredCloneReader* aReader,
uint32_t aTag,
uint32_t aIndex) override;
virtual bool WriteCallback(JSContext* aCx,
JSStructuredCloneWriter* aWriter,
JS::Handle<JSObject*> aObj) override;
virtual bool ReadTransferCallback(JSContext* aCx,
JSStructuredCloneReader* aReader,
uint32_t aTag,
void* aContent,
uint64_t aExtraData,
JS::MutableHandleObject aReturnObject) override;
virtual bool WriteTransferCallback(JSContext* aCx,
JS::Handle<JSObject*> aObj,
uint32_t* aTag,
JS::TransferableOwnership* aOwnership,
void** aContent,
uint64_t* aExtraData) override;
virtual void FreeTransferCallback(uint32_t aTag,
JS::TransferableOwnership aOwnership,
void* aContent,
uint64_t aExtraData) override;
protected:
// If you receive a buffer from IPC, you can use this method to retrieve a
// JS::Value. It can happen that you want to pre-populate the array of Blobs
// and/or the PortIdentifiers.
void ReadFromBuffer(nsISupports* aParent,
JSContext* aCx,
uint64_t* aBuffer,
size_t aBufferLength,
JS::MutableHandle<JS::Value> aValue,
ErrorResult &aRv);
void ReadFromBuffer(nsISupports* aParent,
JSContext* aCx,
uint64_t* aBuffer,
size_t aBufferLength,
uint32_t aAlgorithmVersion,
JS::MutableHandle<JS::Value> aValue,
ErrorResult &aRv);
// Use this method to free a buffer generated by MoveToBuffer().
void FreeBuffer(uint64_t* aBuffer,
size_t aBufferLength);
bool mSupportsCloning;
bool mSupportsTransferring;
ContextSupport mContext;
// Useful for the structured clone algorithm:
nsTArray<nsRefPtr<BlobImpl>> mBlobImplArray;
// This is used for sharing the backend of ImageBitmaps.
// The layers::Image object must be thread-safely reference-counted.
// The layers::Image object will not be written ever via any ImageBitmap
// instance, so no race condition will occur.
nsTArray<nsRefPtr<layers::Image>> mClonedImages;
// This raw pointer is set and unset into the ::Read(). It's always null
// outside that method. For this reason it's a raw pointer.
nsISupports* MOZ_NON_OWNING_REF mParent;
// This array contains the ports once we've finished the reading. It's
// generated from the mPortIdentifiers array.
nsTArray<nsRefPtr<MessagePortBase>> mTransferredPorts;
// This array contains the identifiers of the MessagePorts. Based on these we
// are able to reconnect the new transferred ports with the other
// MessageChannel ports.
nsTArray<MessagePortIdentifier> mPortIdentifiers;
#ifdef DEBUG
nsCOMPtr<nsIThread> mCreationThread;
#endif
};
} // dom namespace
} // mozilla namespace
#endif // mozilla_dom_StructuredCloneHelper_h