gecko-dev/dom/base/ImportManager.h

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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/. */
/*
*
* For each import tree there is one master document (the root) and one
* import manager. The import manager is a map of URI ImportLoader pairs.
* An ImportLoader is responsible for loading an import document from a
* given location, and sending out load or error events to all the link
* nodes that refer to it when it's done. For loading it opens up a
* channel, using the same CSP as the master document. It then creates a
* blank document, and starts parsing the data from the channel. When
* there is no more data on the channel we wait for the DOMContentLoaded
* event from the parsed document. For the duration of the loading
* process the scripts on the parent documents are blocked. When an error
* occurs, or the DOMContentLoaded event is received, the scripts on the
* parent document are unblocked and we emit the corresponding event on
* all the referrer link nodes. If a new link node is added to one of the
* DOM trees in the import tree that refers to an import that was already
* loaded, the already existing ImportLoader is being used (without
* loading the referred import document twice) and if necessary the
* load/error is emitted on it immediately.
*
* Ownership model:
*
* ImportDocument ----------------------------
* ^ |
* | v
* MasterDocument <- ImportManager <-ImportLoader
* ^ ^
* | |
* LinkElement <-----------------------------
*
*/
#ifndef mozilla_dom_ImportManager_h__
#define mozilla_dom_ImportManager_h__
#include "nsTArray.h"
#include "nsCycleCollectionParticipant.h"
#include "nsIDOMEventListener.h"
#include "nsIStreamListener.h"
#include "nsIWeakReferenceUtils.h"
#include "nsRefPtrHashtable.h"
#include "nsScriptLoader.h"
#include "nsURIHashKey.h"
class nsIDocument;
class nsIPrincipal;
class nsINode;
class AutoError;
namespace mozilla {
namespace dom {
class ImportManager;
typedef nsTHashtable<nsPtrHashKey<nsINode>> NodeTable;
class ImportLoader final : public nsIStreamListener
, public nsIDOMEventListener
{
// A helper inner class to decouple the logic of updating the import graph
// after a new import link has been found by one of the parsers.
class Updater {
public:
explicit Updater(ImportLoader* aLoader) : mLoader(aLoader)
{}
// After a new link is added that refers to this import, we
// have to update the spanning tree, since given this new link the
// priority of this import might be higher in the scripts
// execution order than before. It updates mMainReferrer, mImportParent,
// the corresponding pending ScriptRunners, etc.
// It also handles updating additional dependant loaders via the
// UpdateDependants calls.
// (NOTE: See GetMainReferrer about spanning tree.)
void UpdateSpanningTree(nsINode* aNode);
private:
// Returns an array of links that forms a referring chain from
// the master document to this import. Each link in the array
// is marked as main referrer in the list.
void GetReferrerChain(nsINode* aNode, nsTArray<nsINode*>& aResult);
// Once we find a new referrer path to our import, we have to see if
// it changes the load order hence we have to do an update on the graph.
bool ShouldUpdate(nsTArray<nsINode*>& aNewPath);
void UpdateMainReferrer(uint32_t newIdx);
// It's a depth first graph traversal algorithm, for UpdateDependants. The
// nodes in the graph are the import link elements, and there is a directed
// edge from link1 to link2 if link2 is a subimport in the import document
// of link1.
// If the ImportLoader that aCurrentLink points to didn't need to be updated
// the algorithm skips its "children" (subimports). Note, that this graph can
// also contain cycles, aVisistedLinks is used to track the already visited
// links to avoid an infinite loop.
// aPath - (in/out) the referrer link chain of aCurrentLink when called, and
// of the next link when the function returns
// aVisitedLinks - (in/out) list of links that the traversal already visited
// (to handle cycles in the graph)
// aSkipChildren - when aCurrentLink points to an import that did not need
// to be updated, we can skip its sub-imports ('children')
nsINode* NextDependant(nsINode* aCurrentLink,
nsTArray<nsINode*>& aPath,
NodeTable& aVisitedLinks, bool aSkipChildren);
// When we find a new link that changes the load order of the known imports,
// we also have to check all the subimports of it, to see if they need an
// update too. (see test_imports_nested_2.html)
void UpdateDependants(nsINode* aNode, nsTArray<nsINode*>& aPath);
ImportLoader* mLoader;
};
friend class ::AutoError;
friend class ImportManager;
friend class Updater;
public:
ImportLoader(nsIURI* aURI, nsIDocument* aOriginDocument);
NS_DECL_CYCLE_COLLECTING_ISUPPORTS
NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(ImportLoader, nsIStreamListener)
NS_DECL_NSISTREAMLISTENER
NS_DECL_NSIREQUESTOBSERVER
// We need to listen to DOMContentLoaded event to know when the document
// is fully leaded.
NS_IMETHOD HandleEvent(nsIDOMEvent *aEvent) override;
// Validation then opening and starting up the channel.
void Open();
void AddLinkElement(nsINode* aNode);
void RemoveLinkElement(nsINode* aNode);
bool IsReady() { return mReady; }
bool IsStopped() { return mStopped; }
bool IsBlocking() { return mBlockingScripts; }
ImportManager* Manager() {
MOZ_ASSERT(mDocument || mImportParent, "One of them should be always set");
return (mDocument ? mDocument : mImportParent)->ImportManager();
}
// Simply getter for the import document. Can return a partially parsed
// document if called too early.
nsIDocument* GetDocument()
{
return mDocument;
}
// Getter for the import document that is used in the spec. Returns
// nullptr if the import is not yet ready.
nsIDocument* GetImport()
{
if (!mReady) {
return nullptr;
}
return mDocument;
}
// There is only one referring link that is marked as primary link per
// imports. This is the one that has to be taken into account when
// scrip execution order is determined. Links marked as primary link form
// a spanning tree in the import graph. (Eliminating the cycles and
// multiple parents.) This spanning tree is recalculated every time
// a new import link is added to the manager.
nsINode* GetMainReferrer()
{
if (mLinks.IsEmpty()) {
return nullptr;
}
return mLinks[mMainReferrer];
}
// An import is not only blocked by its import children, but also
// by its predecessors. It's enough to find the closest predecessor
// and wait for that to run its scripts. We keep track of all the
// ScriptRunners that are waiting for this import. NOTE: updating
// the main referrer might change this list.
void AddBlockedScriptLoader(nsScriptLoader* aScriptLoader);
bool RemoveBlockedScriptLoader(nsScriptLoader* aScriptLoader);
void SetBlockingPredecessor(ImportLoader* aLoader);
private:
~ImportLoader() {}
// If a new referrer LinkElement was added, let's
// see if we are already finished and if so fire
// the right event.
void DispatchEventIfFinished(nsINode* aNode);
// Dispatch event for a single referrer LinkElement.
void DispatchErrorEvent(nsINode* aNode);
void DispatchLoadEvent(nsINode* aNode);
// Must be called when an error has occured during load.
void Error(bool aUnblockScripts);
// Must be called when the import document has been loaded successfully.
void Done();
// When the reading from the channel and the parsing
// of the document is done, we can release the resources
// that we don't need any longer to hold on.
void ReleaseResources();
// While the document is being loaded we must block scripts
// on the import parent document.
void BlockScripts();
void UnblockScripts();
nsIPrincipal* Principal();
nsCOMPtr<nsIDocument> mDocument;
nsCOMPtr<nsIURI> mURI;
nsCOMPtr<nsIStreamListener> mParserStreamListener;
nsCOMPtr<nsIDocument> mImportParent;
ImportLoader* mBlockingPredecessor;
// List of the LinkElements that are referring to this import
// we need to keep track of them so we can fire event on them.
nsTArray<nsCOMPtr<nsINode>> mLinks;
// List of pending ScriptLoaders that are waiting for this import
// to finish.
nsTArray<RefPtr<nsScriptLoader>> mBlockedScriptLoaders;
// There is always exactly one referrer link that is flagged as
// the main referrer the primary link. This is the one that is
// used in the script execution order calculation.
// ("Branch" according to the spec.)
uint32_t mMainReferrer;
bool mReady;
bool mStopped;
bool mBlockingScripts;
Updater mUpdater;
};
class ImportManager final : public nsISupports
{
typedef nsRefPtrHashtable<nsURIHashKey, ImportLoader> ImportMap;
~ImportManager() {}
public:
ImportManager() {}
NS_DECL_CYCLE_COLLECTING_ISUPPORTS
NS_DECL_CYCLE_COLLECTION_CLASS(ImportManager)
// Finds the ImportLoader that belongs to aImport in the map.
ImportLoader* Find(nsIDocument* aImport);
// Find the ImportLoader aLink refers to.
ImportLoader* Find(nsINode* aLink);
void AddLoaderWithNewURI(ImportLoader* aLoader, nsIURI* aNewURI);
// When a new import link is added, this getter either creates
// a new ImportLoader for it, or returns an existing one if
// it was already created and in the import map.
already_AddRefed<ImportLoader> Get(nsIURI* aURI, nsINode* aNode,
nsIDocument* aOriginDocument);
// It finds the predecessor for an import link node that runs its
// scripts the latest among its predecessors.
ImportLoader* GetNearestPredecessor(nsINode* aNode);
private:
ImportMap mImports;
};
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_ImportManager_h__