/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- * * The contents of this file are subject to the Netscape Public License * Version 1.0 (the "NPL"); you may not use this file except in * compliance with the NPL. You may obtain a copy of the NPL at * http://www.mozilla.org/NPL/ * * Software distributed under the NPL is distributed on an "AS IS" basis, * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL * for the specific language governing rights and limitations under the * NPL. * * The Initial Developer of this code under the NPL is Netscape * Communications Corporation. Portions created by Netscape are * Copyright (C) 1998 Netscape Communications Corporation. All Rights * Reserved. */ /* A sample of XPConnect. This file contains the XPCOM factory the creates for SampleImpl objects. */ #include "nsCOMPtr.h" #include "nscore.h" #include "nsISample.h" #include "nsIComponentManager.h" #include "nsIServiceManager.h" #include "nsXPComFactory.h" /** * IIDs and CIDs (aka CLSIDs) are 32 digit hexadecimal numbers, called Globally * Unique IDs (GUIDs) as a whole. They should only be generated by a trusted * guid generator. GUID generatoration algorithms rely on parameters such as * the MAC address of your NIC, and the date/time of GUID creation to ensure * that no two GUIDs are ever the same. The Windows program 'uuidgen' is one * way to create these numbers. The Unix alternative is probably out there * somewhere. * * NS_DEFINE_IID and NS_DEFINE_CID expand to define static IID/CID objects * that will be used later. IID and CID objects are of the same type, the * distinction between InterfaceID and ClassID is made strictly by what the * ID represents, and not by any binary differences. */ static NS_DEFINE_IID(kISupportsIID, NS_ISUPPORTS_IID); static NS_DEFINE_IID(kIFactoryIID, NS_IFACTORY_IID); static NS_DEFINE_CID(kComponentManagerCID, NS_COMPONENTMANAGER_CID); static NS_DEFINE_CID(kSampleCID, NS_SAMPLE_CID); /** * SampleFactoryImpl is a factory capable of creating nsSampleImpl objects. * It is the factory, as opposed to the class, which actually registers itself * with the XPCOM runtime, in a conversation that goes something like, * XPCOM: "Hello factory at , what can you do for me?", * FACTORY: "Hello XPCOM, I can create the classes named :, * and : and ...". This conversation is initiated when XPCOM calls * into the static NSRegisterSelf function of the shared library that houses this * factory. Once this factory is properly registered, XPCOM can work it's magic. * After registration, any call into the Service Manager or Component Manager's * CreateInstance method requesting a progID or CID that this factory has * registered will cause XPCOM to call the static NSGetFactory function in * the .so, .dll, .whatever associated with this factory (if it hasn't already * done so), and then invoke the CreateInstance method of the resulting factory. */ class SampleFactoryImpl : public nsIFactory { public: SampleFactoryImpl(const nsCID &aClass, const char* className, const char* progID); /** * This macro expands into a declaration of the nsISupports interface. * Every XPCOM component needs to implement nsISupports, as it acts * as the gateway to other interfaces this component implements. You * could manually declare QueryInterface, AddRef, and Release instead * of using this macro, but why? */ // nsISupports methods NS_DECL_ISUPPORTS // nsIFactory methods NS_IMETHOD CreateInstance(nsISupports *aOuter, const nsIID &aIID, void **aResult); NS_IMETHOD LockFactory(PRBool aLock); protected: virtual ~SampleFactoryImpl(); protected: /** * When XPCOM calls into NSGetFactory, it informs us what kind of class * it intends to create with this factory. CreateInstance does NOT get * this information, so we need to record what kind of class CreateInstance * should return for later reference. */ nsCID mClassID; const char* mClassName; const char* mProgID; }; //////////////////////////////////////////////////////////////////////// /** * All the constructor needs does is initailize reference counting and * record the CID/ progID it should return when CreateInstance is called. * Convention dictates a one-to-one mapping between progIDs and CIDs. Think * of a CID as an IP address, and a progID as the canonical name. The * class name is a more descriptive representation of the progID. Classnames * do not have to be unique. */ SampleFactoryImpl::SampleFactoryImpl(const nsCID &aClass, const char* className, const char* progID) : mClassID(aClass), mClassName(className), mProgID(progID) { NS_INIT_REFCNT(); } SampleFactoryImpl::~SampleFactoryImpl() { NS_ASSERTION(mRefCnt == 0, "non-zero refcnt at destruction"); } /** * This is what a normal implementation of QueryInterface (sometimes * abbreviated QI) actually looks like. Because this QI only supports * nsISupports and nsIFactory, it, and the two NS_IMPL_* macros * that follow it could actually be replaced with the macro * NS_IMPL_ISUPPORTS(nsIFactory, nsIFactory::GetIID) as nsSample does * in nsSample.cpp. * The XPCOM homepage (www.mozilla.org/projects/xpcom) has another reference * implementation of QueryInterface. */ NS_IMETHODIMP SampleFactoryImpl::QueryInterface(const nsIID &aIID, void **aResult) { if (! aResult) return NS_ERROR_NULL_POINTER; // Always NULL result, in case of failure *aResult = nsnull; if (aIID.Equals(kISupportsIID)) { *aResult = NS_STATIC_CAST(nsISupports*, this); AddRef(); return NS_OK; } else if (aIID.Equals(kIFactoryIID)) { *aResult = NS_STATIC_CAST(nsIFactory*, this); AddRef(); return NS_OK; } return NS_NOINTERFACE; } NS_IMPL_ADDREF(SampleFactoryImpl); NS_IMPL_RELEASE(SampleFactoryImpl); /** * The IID passed in here is for COM Aggregation. Aggregation deals with * classes contained within other classes, a topic out of the scope of * this sample. * Notice that this CreateInstance is very methodical... It verifies that it * has been asked to create a supported class, even though we only registered * for one, and it calls QI on the newly created object, verifying that the * created class can actually support the interface we thought it could. This * is (probably) regarded as a good thing in CreateInstance, and even if you * think you know whats going to happen in your CreateInstance, it's a good * idea to follow this same formula. */ NS_IMETHODIMP SampleFactoryImpl::CreateInstance(nsISupports *aOuter, const nsIID &aIID, void **aResult) { if (! aResult) return NS_ERROR_NULL_POINTER; if (aOuter) return NS_ERROR_NO_AGGREGATION; *aResult = nsnull; nsresult rv; nsISupports *inst = nsnull; if (mClassID.Equals(kSampleCID)) { if (NS_FAILED(rv = NS_NewSample((nsISample**) &inst))) return rv; } else { return NS_ERROR_NO_INTERFACE; } if (! inst) return NS_ERROR_OUT_OF_MEMORY; if (NS_FAILED(rv = inst->QueryInterface(aIID, aResult))) { // We didn't get the right interface. NS_ERROR("didn't support the interface you wanted"); } NS_IF_RELEASE(inst); return rv; } /** * I'm really not sure what LockFactory would do if it were implemented :( */ nsresult SampleFactoryImpl::LockFactory(PRBool aLock) { // Not implemented in simplest case. return NS_OK; } //////////////////////////////////////////////////////////////////////// /** * The XPCOM runtime will call this to get a new factory object for the * CID/progID it passes in. XPCOM is responsible for caching the resulting * factory. */ // return the proper factory to the caller extern "C" PR_IMPLEMENT(nsresult) NSGetFactory(nsISupports* aServMgr, const nsCID &aClass, const char *aClassName, const char *aProgID, nsIFactory **aFactory) { if (! aFactory) return NS_ERROR_NULL_POINTER; SampleFactoryImpl* factory = new SampleFactoryImpl(aClass, aClassName, aProgID); if (factory == nsnull) return NS_ERROR_OUT_OF_MEMORY; NS_ADDREF(factory); *aFactory = factory; return NS_OK; } /** * When the XPCOM runtime is initialized, it searches the component directory * for shared objects, and attempts to call NSRegisterSelf for each one it * encounters. You are expected to register each component the factory can * create as either a Service or a Component. By convention, Services are * singletons, while Components are not. Services are managed by the * Service Manager, and Components are managed by (what else?) the Component * Manager. The Component Manager itself is a Service, and so you can * retrieve it via the ServiceManager, as this function does. * * If you've gto some spare time, and _really_ want to see whats going on * behind the scenes at registration time, soak up PlatformPrePopulateRegistry * (and all the functions it calls) in * mozilla/xpcom/components/nsComponentManager.cpp */ extern "C" PR_IMPLEMENT(nsresult) NSRegisterSelf(nsISupports* aServMgr , const char* aPath) { nsresult rv; nsCOMPtr servMgr(do_QueryInterface(aServMgr, &rv)); if (NS_FAILED(rv)) return rv; NS_WITH_SERVICE(nsIComponentManager, compMgr, kComponentManagerCID, &rv); if (NS_FAILED(rv)) return rv; rv = compMgr->RegisterComponent(kSampleCID, "Sample World Component", "component://netscape/sample/sample-world", aPath, PR_TRUE, PR_TRUE); if (NS_FAILED(rv)) return rv; return NS_OK; } /** * NSUnregisterSelf is responsible for undoing anything NSRegisterSelf does * to the registry. It would presumably be called if your component is * uninstalled or upgraded. */ extern "C" PR_IMPLEMENT(nsresult) NSUnregisterSelf(nsISupports* aServMgr, const char* aPath) { nsresult rv; nsCOMPtr servMgr(do_QueryInterface(aServMgr, &rv)); if (NS_FAILED(rv)) return rv; NS_WITH_SERVICE(nsIComponentManager, compMgr, kComponentManagerCID, &rv); if (NS_FAILED(rv)) return rv; rv = compMgr->UnregisterComponent(kSampleCID, aPath); if (NS_FAILED(rv)) return rv; return NS_OK; }