Bug 489561 - nsPrincipal should cache nsIPrefBranch and codebase_principal_support pref, r+sr=dveditz, +comments from bz

caps/src/nsPrincipal.cpp

@@ -52,13 +52,77 @@
 #include "nsHashtable.h"
 #include "nsIObjectInputStream.h"
 #include "nsIObjectOutputStream.h"
-#include "nsIPrefBranch.h"
+#include "nsIPrefBranch2.h"
 #include "nsIPrefService.h"
 #include "nsIClassInfoImpl.h"
 #include "nsDOMError.h"
 
 #include "nsPrincipal.h"
 
+class nsCodeBasePrefObserver : nsIObserver
+{
+public:
+  nsCodeBasePrefObserver()
+  {
+    NS_ASSERTION(!sObserverInstalled, "Shouldn't recreate observer\n");
+  }
+  ~nsCodeBasePrefObserver()
+  {
+    sObserverInstalled = PR_FALSE;
+  }
+
+  void Init()
+  {
+    nsCOMPtr<nsIPrefBranch2> prefBranch =
+      do_GetService(NS_PREFSERVICE_CONTRACTID);
+    if (prefBranch) {
+      if (NS_FAILED(prefBranch->GetBoolPref(PrefName(), &sPrefValue))) {
+        sPrefValue = PR_FALSE;
+      }
+      if (NS_SUCCEEDED(prefBranch->AddObserver(PrefName(), this, PR_FALSE))) {
+        sObserverInstalled = PR_TRUE;
+      }
+    }
+  }
+
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHOD Observe(nsISupports* aSubject,
+                     const char* aTopic,
+                     const PRUnichar* aData)
+  {
+    NS_ASSERTION(!strcmp(aTopic,  NS_PREFBRANCH_PREFCHANGE_TOPIC_ID),
+                 "Wrong topic!");
+    NS_ASSERTION(!strcmp(NS_ConvertUTF16toUTF8(aData).get(), PrefName()),
+                 "Wrong pref!");
+
+    nsCOMPtr<nsIPrefBranch> prefBranch(do_QueryInterface(aSubject));
+    if (!prefBranch ||
+        NS_FAILED(prefBranch->GetBoolPref(PrefName(), &sPrefValue))) {
+      sPrefValue = PR_FALSE;
+    }
+    return NS_OK;
+  }
+
+  const char* PrefName()
+  {
+    static const char pref[] = "signed.applets.codebase_principal_support";
+    return pref;
+  }
+
+  static PRBool PrefValue() { return sPrefValue; }
+  static PRBool Installed() { return sObserverInstalled; }
+
+
+protected:
+  static PRBool sPrefValue;
+  static PRBool sObserverInstalled;
+};
+
+PRBool nsCodeBasePrefObserver::sPrefValue = PR_FALSE;
+PRBool nsCodeBasePrefObserver::sObserverInstalled = PR_FALSE;
+NS_IMPL_ISUPPORTS1(nsCodeBasePrefObserver, nsIObserver)
+
 static PRBool URIIsImmutable(nsIURI* aURI)
 {
   nsCOMPtr<nsIMutable> mutableObj(do_QueryInterface(aURI));
@@ -112,6 +176,13 @@ nsPrincipal::nsPrincipal()
     mCodebaseImmutable(PR_FALSE),
     mDomainImmutable(PR_FALSE)
 {
+  if (!nsCodeBasePrefObserver::Installed()) {
+    nsRefPtr<nsCodeBasePrefObserver> obs = new nsCodeBasePrefObserver();
+    if (obs)
+      obs->Init();
+    NS_WARN_IF_FALSE(nsCodeBasePrefObserver::Installed(),
+                     "Installing nsCodeBasePrefObserver failed!");
+  }
 }
 
 nsresult
@@ -425,21 +496,15 @@ nsPrincipal::CanEnableCapability(const char *capability, PRInt16 *result)
     // schemes are special and may be able to get extra capabilities
     // even with the pref disabled.
 
-    static const char pref[] = "signed.applets.codebase_principal_support";
-    nsCOMPtr<nsIPrefBranch> prefBranch =
-      do_GetService(NS_PREFSERVICE_CONTRACTID);
-    if (prefBranch) {
-      PRBool mightEnable;
-      nsresult rv = prefBranch->GetBoolPref(pref, &mightEnable);
+    if (!nsCodeBasePrefObserver::PrefValue()) {
+      PRBool mightEnable = PR_FALSE;
+      nsresult rv = mCodebase->SchemeIs("file", &mightEnable);
       if (NS_FAILED(rv) || !mightEnable) {
-        rv = mCodebase->SchemeIs("file", &mightEnable);
+        rv = mCodebase->SchemeIs("resource", &mightEnable);
         if (NS_FAILED(rv) || !mightEnable) {
-          rv = mCodebase->SchemeIs("resource", &mightEnable);
-          if (NS_FAILED(rv) || !mightEnable) {
-            *result = nsIPrincipal::ENABLE_DENIED;
+          *result = nsIPrincipal::ENABLE_DENIED;
 
-            return NS_OK;
-          }
+          return NS_OK;
         }
       }
     }