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gecko-dev/xpcom/components/mozIClassRegistry.h

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C
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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
* 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.
*/
#ifndef __mozIClassRegistry_h
#define __mozIClassRegistry_h
#include "nsIComponentManager.h"
/*---------------------------- mozIClassRegistry -------------------------------
| This interface provides access to a mapping from mnemonic interface names |
| to shared libraries where implementations of those interfaces can be located.|
| |
| This interface is designed to provide two things: |
| 1. A means of less static binding between clients and the code that |
| implements the XPCOM interfaces those clients use. This accomplished |
| by the mapping from interface names to nsCID (and the shared libraries |
| that implement those classes). |
| 2. A means of dynamically changing the mapping from interface name to |
| implementation. The canonical example of this is to switch to a |
| "native" widget set versus an "XP" (implemented using gfx) set. |
| |
| The first goal is achieved by storing (in a "Netscape Registry" file, see |
| nsReg.h) information that maps interface/class "names" to information about |
| where to load implementations of those interfaces. That information |
| includes the interface ID, class ID (of the implementation class), and the |
| name of the shared library that contains the implementation. |
| |
| The class registry object will register those classes with the "repository" |
| (see nsComponentManager.h) the first time a request is made to create an |
| instance. Subsequent requests will simply be forwarded to the repository |
| after the appropriate interface and class IDs are determined. |
| |
| The second goal is accomplished by permitting the mnemonic interface |
| "names" to be "overloaded", that is, mapped to distinct implementations |
| by separate class registry objects. Further, class registries can be |
| cascaded: they can be chained together so that when a name is not |
| recognized by one registry, it can pass the request to the next registry in |
| the chain. Users can control resolution by making the request of a |
| registry further up/down the chain. |
| |
| For example, consider the case of "native" vs. "gfx" widgets. This might |
| be structured by a class registry arrangment like this: |
| |
| nativeWidgetRegistry baseWidgetRegistry |
| +----------+ +----------+ |
| | ----+---------------->| | |
| +----------+ +----------+ |
| |toolbar| -+-----+ |toolbar| -+-----+ |
| +----------+ | +----------+ | |
| |button | -+-----+ |button | -+-----+ |
| +----------+ | +----------+ | |
| V V |
| +-----------------+ +-----------------+ |
| | native.dll | | base.dll | |
| +-----------------+ +-----------------+ |
| |
| If a specialized implementation of widgets is present (e.g., native.dll) |
| then a corresponding class registry object is created and added to the |
| head of the registry chain. Object creation requests (normal ones) are |
| resolved to the native implementation. If such a library is not present, |
| then the resolution is to the base implementation. If objects of the |
| base implementation are required, then creation requests can be directed |
| directly to the baseWidgetRegistry object, rather than the head of the |
| registry chain. |
| |
| It is intended that there be a single instance of this interface, accessed |
| via the Service Manager (see nsServiceManager.h). |
------------------------------------------------------------------------------*/
struct mozIClassRegistry : public ISupports {
/*------------------------------ CreateInstance ----------------------------
| Create an instance of the requested class/interface. The interface |
| ID is required to specify how the result will be treated. The class |
| named by aName must support this interface. The result is placed in |
| ncomment aResult (NULL if the request fails). "start" specifies the |
| registry at which the search for an implementation of the named |
| interface should start. It defaults to 0 (indicating to start at the |
| head of the registry chain). |
--------------------------------------------------------------------------*/
NS_IMETHOD CreateInstance( const char *anInterfaceName,
const nsIID &aIID,
void* *aResult,
const char *start = 0 ) = 0;
/*--------------------------- CreateEnumerator -----------------------------
| Creates an nsIEnumerator interface object that can be used to examine |
| the contents of the registry. "pattern" specifies either "*" or the |
| name of a specific interface that you want to query. "result" will |
| be set to point to a new object (which will be freed on the last call |
| to its Release() member). See nsIEnumerator.h for details on how to |
| use the returned interface pointer. |
--------------------------------------------------------------------------*/
NS_IMETHOD CreateEnumerator( const char *pattern,
nsIEnumerator* *result ) = 0;
}; // mozIClassRegistry
/*-------------------------- mozIClassRegistryEntry ----------------------------
| Objects of this class represent the individual elements that comprise a |
| mozIClassRegistry interface. You obtain such objects by applying the |
| CreateEnumerator member function to the class registry and then applying |
| the CurrentItem member function to the resulting nsIEnumerator interface. |
| |
| Each entry can be queried for the following information: |
| o sub-registry name |
| o interface name |
| o Class ID |
| o IIDs implemented |
| |
| The information obtained from the entry (specifically, the const char* |
| strings) remains valid for the life of the entry (i.e., until you |
| Release() it). |
| |
| Here is an example of code that uses this interface to dump the contents |
| of a mozIClassRegistry: |
| |
| mozIClassRegistry *reg = nsServiceManager::GetService( kIDRegistry ); |
| nsIEnumerator *enum; |
| reg->CreateEnumerator( "*", &enum ); |
| for ( enum->First(); !enum->IsDone(); enum->Next(); ) { |
| mozIClassRegistryEntry *entry; |
| enum->CurrentItem( &entry ); |
| const char *subreg; |
| const char *name; |
| nsCID cid; |
| int numIIDs; |
| entry->GetSubRegistryName( &subreg ); |
| entry->GetInterfaceName( &name ); |
| entry->GetClassID( &cid ); |
| entry->GetNumIIDs( &numIIDs ); |
| cout << subreg << "/" << name << " = " << cid.ToString() << endl; |
| for ( int i = 0; i < numIIDs; i++ ) { |
| nsIID iid; |
| entry->GetInterfaceID( i, &iid ); |
| cout << "/tIID[" << i << "] = " << iid.ToString() << endl; |
| } |
| entry->Release(); |
| } |
| enum->Release(); |
------------------------------------------------------------------------------*/
struct mozIClassRegistryEntry : public nsISupports {
NS_IMETHOD GetSubRegistryName( const char **result ) = 0;
NS_IMETHOD GetInterfaceName( const char **result ) = 0;
NS_IMETHOD GetClassID( nsCID *result ) = 0;
NS_IMETHOD GetNumIIDs( int *result ) = 0;
NS_IMETHOD GetInterfaceID( int n, nsIID *result ) = 0;
}; // mozIClassRegistryEntry
// {5D41A440-8E37-11d2-8059-00600811A9C3}
#define MOZ_ICLASSREGISTRY_IID { 0x5d41a440, 0x8e37, 0x11d2, { 0x80, 0x59, 0x0, 0x60, 0x8, 0x11, 0xa9, 0xc3 } }
// {D1B54831-AC07-11d2-805E-00600811A9C3}
#define MOZ_ICLASSREGISTRYENTRY_IID { 0xd1b54831, 0xac07, 0x11d2, { 0x80, 0x5e, 0x0, 0x60, 0x8, 0x11, 0xa9, 0xc3 } }
#endif
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