Bug 1407494 (part 9) - Merge PREF_RegisterCallback() and PREF_RegisterPriorityCallback. r=glandium.

This avoids some code duplication.

MozReview-Commit-ID: 2Cb4YtL5RSu

modules/libpref/Preferences.cpp

@@ -373,13 +373,10 @@ PREF_ClearAllUserPrefs();
 // returns PREF_NOERROR if a callback was found that matched all the
 // parameters; otherwise it returns PREF_ERROR.
 void
-PREF_RegisterPriorityCallback(const char* aPrefNode,
-                              PrefChangedFunc aCallback,
-                              void* aData);
-void
 PREF_RegisterCallback(const char* aPrefNode,
                       PrefChangedFunc aCallback,
-                      void* aData);
+                      void* aData,
+                      bool aIsPriority);
 nsresult
 PREF_UnregisterCallback(const char* aPrefNode,
                         PrefChangedFunc aCallback,
@@ -450,6 +447,8 @@ PLDHashTable* gHashTable;
 
 static ArenaAllocator<8192, 4> gPrefNameArena;
 
+// The callback list contains all the priority callbacks followed by the
+// non-priority callbacks. gLastPriorityNode records where the first part ends.
 static CallbackNode* gFirstCallback = nullptr;
 static CallbackNode* gLastPriorityNode = nullptr;
 
@@ -1302,11 +1301,12 @@ PREF_PrefIsLocked(const char* aPrefName)
   return result;
 }
 
-// Adds a node to the beginning of the callback list.
+// Adds a node to the callback list; the position depends on aIsPriority.
 void
-PREF_RegisterPriorityCallback(const char* aPrefNode,
+PREF_RegisterCallback(const char* aPrefNode,
                       PrefChangedFunc aCallback,
-                              void* aData)
+                      void* aData,
+                      bool aIsPriority)
 {
   NS_PRECONDITION(aPrefNode, "aPrefNode must not be nullptr");
   NS_PRECONDITION(aCallback, "aCallback must not be nullptr");
@@ -1315,26 +1315,16 @@ PREF_RegisterPriorityCallback(const char* aPrefNode,
   node->mDomain = moz_xstrdup(aPrefNode);
   node->mFunc = aCallback;
   node->mData = aData;
+
+  if (aIsPriority) {
+    // Add to the start of the list.
     node->mNext = gFirstCallback;
     gFirstCallback = node;
     if (!gLastPriorityNode) {
       gLastPriorityNode = node;
     }
-}
+  } else {
-
+    // Add to the start of the non-priority part of the list.
-// Adds a node to the end of the callback list.
-void
-PREF_RegisterCallback(const char* aPrefNode,
-                      PrefChangedFunc aCallback,
-                      void* aData)
-{
-  NS_PRECONDITION(aPrefNode, "aPrefNode must not be nullptr");
-  NS_PRECONDITION(aCallback, "aCallback must not be nullptr");
-
-  auto node = new CallbackNode();
-  node->mDomain = moz_xstrdup(aPrefNode);
-  node->mFunc = aCallback;
-  node->mData = aData;
     if (gLastPriorityNode) {
       node->mNext = gLastPriorityNode->mNext;
       gLastPriorityNode->mNext = node;
@@ -1343,6 +1333,7 @@ PREF_RegisterCallback(const char* aPrefNode,
       gFirstCallback = node;
     }
   }
+}
 
 // Removes |node| from callback list. Returns the node after the deleted one.
 CallbackNode*
@@ -3176,7 +3167,8 @@ nsPrefBranch::AddObserver(const char* aDomain,
   // aDomain == nullptr is the only possible failure, and we trapped it with
   // NS_ENSURE_ARG above.
   const PrefName& pref = GetPrefName(aDomain);
-  PREF_RegisterCallback(pref.get(), NotifyObserver, pCallback);
+  PREF_RegisterCallback(
+    pref.get(), NotifyObserver, pCallback, /* isPriority */ false);
   return NS_OK;
 }
 
@@ -5338,8 +5330,10 @@ RegisterPriorityCallback(PrefChangedFunc aCallback,
 
   observer = new ValueObserver(aPref, aCallback, Preferences::ExactMatch);
   observer->AppendClosure(aClosure);
-  PREF_RegisterPriorityCallback(
+  PREF_RegisterCallback(aPref,
-    aPref, NotifyObserver, static_cast<nsIObserver*>(observer));
+                        NotifyObserver,
+                        static_cast<nsIObserver*>(observer),
+                        /* isPriority */ true);
   gObserverTable->Put(observer, observer);
 }