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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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_UnderlyingSourceCallbackHelpers_h
#define mozilla_dom_UnderlyingSourceCallbackHelpers_h
#include "mozilla/HoldDropJSObjects.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/UnderlyingSourceBinding.h"
#include "nsISupports.h"
#include "nsISupportsImpl.h"
/* Since the streams specification has native descriptions of some callbacks
* (i.e. described in prose, rather than provided by user code), we need to be
* able to pass around native callbacks. To handle this, we define polymorphic
* classes That cover the difference between native callback and user-provided.
*
* The Streams specification wants us to invoke these callbacks, run through
* WebIDL as if they were methods. So we have to preserve the underlying object
* to use as the This value on invocation.
*/
namespace mozilla::dom {
class BodyStreamHolder;
class ReadableStreamController;
class UnderlyingSourceAlgorithmsBase : public nsISupports {
public:
NS_DECL_CYCLE_COLLECTING_ISUPPORTS
NS_DECL_CYCLE_COLLECTION_CLASS(UnderlyingSourceAlgorithmsBase)
MOZ_CAN_RUN_SCRIPT virtual void StartCallback(
JSContext* aCx, ReadableStreamController& aController,
JS::MutableHandle<JS::Value> aRetVal, ErrorResult& aRv) = 0;
// A promise-returning algorithm that pulls data from the underlying byte
// source
MOZ_CAN_RUN_SCRIPT virtual already_AddRefed<Promise> PullCallback(
JSContext* aCx, ReadableStreamController& aController,
ErrorResult& aRv) = 0;
// A promise-returning algorithm, taking one argument (the cancel reason),
// which communicates a requested cancelation to the underlying byte source
MOZ_CAN_RUN_SCRIPT virtual already_AddRefed<Promise> CancelCallback(
JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aReason,
ErrorResult& aRv) = 0;
// Implement this when you need to release underlying resources immediately
// from closed(canceled)/errored streams, without waiting for GC.
virtual void ReleaseObjects() {}
// Fetch wants to special-case BodyStream-based streams
virtual BodyStreamHolder* GetBodyStreamHolder() { return nullptr; }
// https://streams.spec.whatwg.org/#other-specs-rs-create
// By "native" we mean "instances initialized via the above set up or set up
// with byte reading support algorithms (not, e.g., on web-developer-created
// instances)"
virtual bool IsNative() { return true; }
protected:
virtual ~UnderlyingSourceAlgorithmsBase() = default;
};
class UnderlyingSourceAlgorithms final : public UnderlyingSourceAlgorithmsBase {
public:
NS_DECL_ISUPPORTS_INHERITED
NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(
UnderlyingSourceAlgorithms, UnderlyingSourceAlgorithmsBase)
UnderlyingSourceAlgorithms(nsIGlobalObject* aGlobal,
JS::Handle<JSObject*> aUnderlyingSource,
UnderlyingSource& aUnderlyingSourceDict)
: mGlobal(aGlobal), mUnderlyingSource(aUnderlyingSource) {
// Step 6. (implicit Step 2.)
if (aUnderlyingSourceDict.mStart.WasPassed()) {
mStartCallback = aUnderlyingSourceDict.mStart.Value();
}
// Step 7. (implicit Step 3.)
if (aUnderlyingSourceDict.mPull.WasPassed()) {
mPullCallback = aUnderlyingSourceDict.mPull.Value();
}
// Step 8. (implicit Step 4.)
if (aUnderlyingSourceDict.mCancel.WasPassed()) {
mCancelCallback = aUnderlyingSourceDict.mCancel.Value();
}
mozilla::HoldJSObjects(this);
};
MOZ_CAN_RUN_SCRIPT void StartCallback(JSContext* aCx,
ReadableStreamController& aController,
JS::MutableHandle<JS::Value> aRetVal,
ErrorResult& aRv) override;
MOZ_CAN_RUN_SCRIPT already_AddRefed<Promise> PullCallback(
JSContext* aCx, ReadableStreamController& aController,
ErrorResult& aRv) override;
MOZ_CAN_RUN_SCRIPT already_AddRefed<Promise> CancelCallback(
JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aReason,
ErrorResult& aRv) override;
bool IsNative() override { return false; }
protected:
~UnderlyingSourceAlgorithms() override { mozilla::DropJSObjects(this); };
private:
// Virtually const, but are cycle collected
nsCOMPtr<nsIGlobalObject> mGlobal;
JS::Heap<JSObject*> mUnderlyingSource;
MOZ_KNOWN_LIVE RefPtr<UnderlyingSourceStartCallback> mStartCallback;
MOZ_KNOWN_LIVE RefPtr<UnderlyingSourcePullCallback> mPullCallback;
MOZ_KNOWN_LIVE RefPtr<UnderlyingSourceCancelCallback> mCancelCallback;
};
} // namespace mozilla::dom
#endif
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