pjs/rdf/base/public/nsIRDFService.h

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/* -*- 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.
*/
/*
The RDF service interface. This is a singleton object, and should be
obtained from the <tt>nsServiceManager</tt>.
XXX I'm not particularly happy with the current APIs for named data
sources. The idea is that you want "rdf:bookmarks" to always map to
the "bookmarks" data store. The thing that bothers me now is that
the implementation has to pre-load all of the data sources: that
means you need to parse the bookmarks file, read the history, etc.,
rather than doing this on-demand. With a little thought, it may be
able to enormously improve these APIs so that pre-loading data
sources is unnecessary.
*/
#ifndef nsIRDFService_h__
#define nsIRDFService_h__
#include "nscore.h"
#include "nsISupports.h"
class nsIRDFDataBase;
class nsIRDFDataSource;
class nsIRDFLiteral;
class nsIRDFResource;
// {BFD05261-834C-11d2-8EAC-00805F29F370}
#define NS_IRDFSERVICE_IID \
{ 0xbfd05261, 0x834c, 0x11d2, { 0x8e, 0xac, 0x0, 0x80, 0x5f, 0x29, 0xf3, 0x70 } }
class nsIRDFService : public nsISupports {
public:
static const nsIID& IID() { static nsIID iid = NS_IRDFSERVICE_IID; return iid; }
// Resource management routines
/**
* Construct an RDF resource from a single-byte URI. <tt>nsIRDFSerivce</tt>
* caches resources that are in-use, so multiple calls to <tt>GetResource()</tt>
* for the same <tt>uri</tt> will return identical pointers.
*/
NS_IMETHOD GetResource(const char* uri, nsIRDFResource** resource) = 0;
/**
* Construct an RDF resource from a Unicode URI. This is provided
* as a convenience method, allowing automatic, in-line C++
* conversion from <tt>nsString</tt> objects. The <tt>uri</tt> will
* be converted to a single-byte representation internally.
*/
NS_IMETHOD GetUnicodeResource(const PRUnichar* uri, nsIRDFResource** resource) = 0;
/**
* Construct an RDF literal from a Unicode string.
*/
NS_IMETHOD GetLiteral(const PRUnichar* value, nsIRDFLiteral** literal) = 0;
/**
* Registers a resource with the RDF system, making it unique w.r.t.
* GetResource.
*
* An implementation of nsIRDFResource should call this in its
* Init() method if it wishes the resource to be globally unique
* (which is usually the case).
*
* NOTE that the resource will <i>not</i> be ref-counted by the
* RDF service: the assumption is that the resource implementation
* will call nsIRDFService::UnregisterResource() when the last
* reference to the resource is released.
*
* NOTE that the nsIRDFService implementation may choose to
* maintain a reference to the resource's URI; therefore, the
* resource implementation should ensure that the resource's URI
* (accessable via nsIRDFResource::GetValue(const char* *aURI)) is
* valid before calling RegisterResource(). Furthermore, the
* resource implementation should ensure that this pointer
* <i>remains</i> valid for the lifetime of the resource. (The
* implementation of the resource cache in nsIRDFService uses the
* URI maintained "internally" in the resource as a key into the
* cache rather than copying the resource URI itself.)
*/
NS_IMETHOD RegisterResource(nsIRDFResource* aResource, PRBool replace = PR_FALSE) = 0;
/**
* Called to notify the resource manager that a resource is no
* longer in use. This method should only be called from the
* destructor of a "custom" resource implementation to notify the
* RDF service that the last reference to the resource has been
* released, so the resource is no longer valid.
*
* NOTE. As mentioned in nsIRDFResourceFactory::CreateResource(),
* the RDF service will use the result of
* nsIRDFResource::GetValue() as a key into its cache. For this
* reason, you must always un-cache the resource <b>before</b>
* releasing the storage for the <tt>const char*</tt> URI.
*/
NS_IMETHOD UnregisterResource(nsIRDFResource* aResource) = 0;
// Data source management routines
/**
* Register a <i>named data source</i>. The RDF service will call
* <tt>nsIRDFDataSource::GetURI()</tt> to determine the URI under
* which to register the data source.
*
* Note that the data source will <i>not</i> be refcounted by the
* RDF service! The assumption is that an RDF data source
* registers with the service once it is initialized (via
* <tt>nsIRDFDataSource::Init()</tt>), and unregisters when the
* last reference to the data source is released.
*/
NS_IMETHOD RegisterDataSource(nsIRDFDataSource* dataSource,
PRBool replace = PR_FALSE) = 0;
/**
* Unregister a <i>named data source</i>. The RDF service will call
* <tt>nsIRDFDataSource::GetURI()</tt> to determine the URI under which the
* data source was registered.
*/
NS_IMETHOD UnregisterDataSource(nsIRDFDataSource* dataSource) = 0;
/**
* Get the <i>named data source</i> corresponding to the URI. If a data
* source has been registered via <tt>RegisterDataSource()</tt>, that
* data source will be returned.
*
* If no data source is currently
* registered for the specified URI, and a data source <i>constructor</i>
* function has been registered via <tt>RegisterDatasourceConstructor()</tt>,
* the RDF service will call the constructor to attempt to construct a
* new data source. If construction is successful, the data source will
* be initialized via <tt>nsIRDFDataSource::Init()</tt>.
*/
NS_IMETHOD GetDataSource(const char* uri, nsIRDFDataSource** dataSource) = 0;
/**
* Create a database that contains the specified named data
* sources. This is a convenience method whose functionality is
* equivalent to (1) constructing a new nsIRDFDataBase object from
* the repository, and (2) iteratively adding the named data sources
* to it, in order.
*/
NS_IMETHOD CreateDatabase(const char** uris, nsIRDFDataBase** dataBase) = 0;
/**
* Get the database aggregating all the stuff that Navigator sees as a default,
* including a "local" store.
*/
NS_IMETHOD CreateBrowserDatabase(nsIRDFDataBase** dataBase) = 0;
};
extern nsresult
NS_NewRDFService(nsIRDFService** result);
#endif // nsIRDFService_h__