Add experimental support for RDF delegates.

rdf/base/idl/nsIRDFDelegateFactory.idl

@@ -33,7 +33,7 @@ interface nsIRDFResource;
 
 /**
  * This interface should be implemented by an XPCOM factory that
- * is registered to handle "component:/rdf/delegate/[key]/[scheme]"
+ * is registered to handle "component:/rdf/delegate-factory/[key]/[scheme]"
  * ProgIDs.
  *
  * The factory will be invoked to create delegate objects from

rdf/base/idl/nsIRDFResource.idl

@@ -20,6 +20,7 @@
  * Contributor(s): 
  */
 
+#include "nsrootidl.idl"
 #include "nsIRDFNode.idl"
 
 
@@ -51,5 +52,39 @@ interface nsIRDFResource : nsIRDFNode {
      * Determine if the resource has the given URI.
      */
     boolean EqualsString(in string aURI);
+
+    /**
+     * Retrieve the "delegate" object for this resource. A resource
+     * may have several delegate objects, each of whose lifetimes is
+     * bound to the life of the resource object.
+     *
+     * This method will return the delegate for the given key after
+     * QueryInterface()-ing it to the requested IID.
+     *
+     * If no delegate exists for the specified key, this method will
+     * attempt to create one using the component manager. Specifically,
+     * it will combine aKey with the resource's URI scheme to produce
+     * a ProgID as follows:
+     *
+     *   component:/rdf/delegate-factory/[key]/[scheme]
+     *
+     * This ProgID will be used to locate a factory using the
+     * FindFactory() method of nsIComponentManager. If the nsIFactory
+     * exists, it will be used to create a "delegate factory"; that
+     * is, an object that supports nsIRDFDelegateFactory. The delegate
+     * factory will be used to construct the delegate object.
+     */
+    void GetDelegate(in string aKey, in nsIIDRef aIID,
+                     [iid_is(aIID),retval] out nsQIResult aResult);
+
+    /**
+     * Force a delegate to be "unbound" from the resource.
+     *
+     * Normally, a delegate object's lifetime will be identical to
+     * that of the resource to which it is bound; this method allows a
+     * delegate to unlink itself from an RDF resource prematurely.
+     */
+    void ReleaseDelegate(in string aKey);
 };
 
+

rdf/util/public/nsRDFResource.h

@@ -23,9 +23,11 @@
 #ifndef nsRDFResource_h__
 #define nsRDFResource_h__
 
+#include "nsCOMPtr.h"
 #include "nsIRDFNode.h"
 #include "nsIRDFResource.h"
 #include "nscore.h"
+#include "nsString.h"
 #include "rdf.h"
 class nsIRDFService;
 
@@ -46,6 +48,8 @@ public:
     NS_IMETHOD GetValue(char* *aURI);
     NS_IMETHOD GetValueConst(const char** aURI);
     NS_IMETHOD EqualsString(const char* aURI, PRBool* aResult);
+    NS_IMETHOD GetDelegate(const char* aKey, REFNSIID aIID, void** aResult);
+    NS_IMETHOD ReleaseDelegate(const char* aKey);
 
     // nsRDFResource methods:
     nsRDFResource(void);
@@ -57,6 +61,14 @@ protected:
 
 protected:
     char* mURI;
+
+    struct DelegateEntry {
+        nsCString             mKey;
+        nsCOMPtr<nsISupports> mDelegate;
+        DelegateEntry*        mNext;
+    };
+
+    DelegateEntry* mDelegates;
 };
 
 #endif // nsRDFResource_h__

rdf/util/src/nsRDFResource.cpp

@@ -23,6 +23,7 @@
 #include "nsRDFResource.h"
 #include "nsCRT.h"
 #include "nsIServiceManager.h"
+#include "nsIRDFDelegateFactory.h"
 #include "nsIRDFService.h"
 #include "nsRDFCID.h"
 #include "nsXPIDLString.h"
@@ -37,13 +38,20 @@ nsrefcnt nsRDFResource::gRDFServiceRefCnt = 0;
 ////////////////////////////////////////////////////////////////////////////////
 
 nsRDFResource::nsRDFResource(void)
-    : mURI(nsnull)
+    : mURI(nsnull), mDelegates(nsnull)
 {
     NS_INIT_REFCNT();
 }
 
 nsRDFResource::~nsRDFResource(void)
 {
+    // Release all of the delegate objects
+    while (mDelegates) {
+        DelegateEntry* doomed = mDelegates;
+        mDelegates = mDelegates->mNext;
+        delete doomed;
+    }
+
     gRDFService->UnregisterResource(this);
 
     // N.B. that we need to free the URI *after* we un-cache the resource,
@@ -166,4 +174,85 @@ nsRDFResource::EqualsString(const char* aURI, PRBool* aResult)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsRDFResource::GetDelegate(const char* aKey, REFNSIID aIID, void** aResult)
+{
+    NS_PRECONDITION(aKey != nsnull, "null ptr");
+    if (! aKey)
+        return NS_ERROR_NULL_POINTER;
+
+    nsresult rv;
+    *aResult = nsnull;
+
+    DelegateEntry* entry = mDelegates;
+    while (entry) {
+        if (entry->mKey == aKey) {
+            rv = entry->mDelegate->QueryInterface(aIID, aResult);
+            return rv;
+        }
+
+        entry = entry->mNext;
+    }
+
+    // Construct a ProgID of the form "component:/rdf/delegate/[key]/[scheme]
+    nsCAutoString progID("component://rdf/delegate-factory/");
+    progID.Append(aKey);
+    progID.Append("/");
+
+    for (const char* p = mURI; *p && *p != ':'; ++p)
+        progID.Append(*p);
+
+    nsCOMPtr<nsIRDFDelegateFactory> delegateFactory;
+    rv = nsComponentManager::CreateInstance(progID,
+                                            nsnull,
+                                            NS_GET_IID(nsIRDFDelegateFactory),
+                                            getter_AddRefs(delegateFactory));
+    if (NS_FAILED(rv)) return rv;
+
+    rv = delegateFactory->CreateDelegate(this, aKey, aIID, aResult);
+    if (NS_FAILED(rv)) return rv;
+
+    // Okay, we've successfully created a delegate. Let's remember it.
+    entry = new DelegateEntry;
+    if (! entry) {
+        NS_RELEASE(*NS_REINTERPRET_CAST(nsISupports**, aResult));
+        return NS_ERROR_OUT_OF_MEMORY;
+    }
+    
+    entry->mKey      = aKey;
+    entry->mDelegate = do_QueryInterface(*NS_REINTERPRET_CAST(nsISupports**, aResult));
+    entry->mNext     = mDelegates;
+
+    mDelegates = entry;
+
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsRDFResource::ReleaseDelegate(const char* aKey)
+{
+    NS_PRECONDITION(aKey != nsnull, "null ptr");
+    if (! aKey)
+        return NS_ERROR_NULL_POINTER;
+
+    DelegateEntry* entry = mDelegates;
+    DelegateEntry** link = &mDelegates;
+
+    while (entry) {
+        if (entry->mKey == aKey) {
+            *link = entry->mNext;
+            delete entry;
+            return NS_OK;
+        }
+
+        link = &(entry->mNext);
+        entry = entry->mNext;
+    }
+
+    NS_WARNING("nsRDFResource::ReleaseDelegate() no delegate found");
+    return NS_OK;
+}
+
+
+
 ////////////////////////////////////////////////////////////////////////////////