forked from mirrors/gecko-dev
123 lines
3.3 KiB
C++
123 lines
3.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsCategoryCache_h_
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#define nsCategoryCache_h_
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#include "mozilla/Attributes.h"
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#include "nsIObserver.h"
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#include "nsServiceManagerUtils.h"
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#include "nsCOMArray.h"
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#include "nsInterfaceHashtable.h"
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#include "nsXPCOM.h"
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#include "MainThreadUtils.h"
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class nsCategoryObserver final : public nsIObserver {
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~nsCategoryObserver();
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public:
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explicit nsCategoryObserver(const nsACString& aCategory);
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void ListenerDied();
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void SetListener(void(aCallback)(void*), void* aClosure);
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nsInterfaceHashtable<nsCStringHashKey, nsISupports>& GetHash() {
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return mHash;
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}
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NS_DECL_ISUPPORTS
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NS_DECL_NSIOBSERVER
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private:
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void RemoveObservers();
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nsInterfaceHashtable<nsCStringHashKey, nsISupports> mHash;
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nsCString mCategory;
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void (*mCallback)(void*);
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void* mClosure;
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bool mObserversRemoved;
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};
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/**
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* This is a helper class that caches services that are registered in a certain
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* category. The intended usage is that a service stores a variable of type
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* nsCategoryCache<nsIFoo> in a member variable, where nsIFoo is the interface
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* that these services should implement. The constructor of this class should
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* then get the name of the category.
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*/
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template <class T>
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class nsCategoryCache final {
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public:
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explicit nsCategoryCache(const char* aCategory) : mCategoryName(aCategory) {
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MOZ_ASSERT(NS_IsMainThread());
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}
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~nsCategoryCache() {
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MOZ_ASSERT(NS_IsMainThread());
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if (mObserver) {
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mObserver->ListenerDied();
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}
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}
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void GetEntries(nsCOMArray<T>& aResult) {
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MOZ_ASSERT(NS_IsMainThread());
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LazyInit();
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AddEntries(aResult);
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}
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/**
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* This function returns an nsCOMArray of interface pointers to the cached
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* category enries for the requested category. This was added in order to be
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* used in call sites where the overhead of excessive allocations can be
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* unacceptable. See bug 1360971 for an example.
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*/
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const nsCOMArray<T>& GetCachedEntries() {
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MOZ_ASSERT(NS_IsMainThread());
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LazyInit();
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if (mCachedEntries.IsEmpty()) {
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AddEntries(mCachedEntries);
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}
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return mCachedEntries;
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}
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private:
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void LazyInit() {
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// Lazy initialization, so that services in this category can't
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// cause reentrant getService (bug 386376)
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if (!mObserver) {
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mObserver = new nsCategoryObserver(mCategoryName);
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mObserver->SetListener(nsCategoryCache<T>::OnCategoryChanged, this);
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}
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}
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void AddEntries(nsCOMArray<T>& aResult) {
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for (nsISupports* entry : mObserver->GetHash().Values()) {
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nsCOMPtr<T> service = do_QueryInterface(entry);
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if (service) {
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aResult.AppendElement(service.forget());
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}
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}
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}
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static void OnCategoryChanged(void* aClosure) {
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MOZ_ASSERT(NS_IsMainThread());
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auto self = static_cast<nsCategoryCache<T>*>(aClosure);
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self->mCachedEntries.Clear();
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}
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private:
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// Not to be implemented
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nsCategoryCache(const nsCategoryCache<T>&);
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nsCString mCategoryName;
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RefPtr<nsCategoryObserver> mObserver;
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nsCOMArray<T> mCachedEntries;
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};
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#endif
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