Support multiple HRTFDatabases for different sample-rates

Source/core/platform/audio/HRTFDatabaseLoader.h

Index: Source/core/platform/audio/HRTFDatabaseLoader.h
diff --git a/Source/core/platform/audio/HRTFDatabaseLoader.h b/Source/core/platform/audio/HRTFDatabaseLoader.h
index 4562db7665e52b54512937aaab2486f5484cf62d..701ddb35862383c6ddd2bba5a7309310fd33c4b2 100644
--- a/Source/core/platform/audio/HRTFDatabaseLoader.h
+++ b/Source/core/platform/audio/HRTFDatabaseLoader.h
@@ -30,10 +30,11 @@
 #define HRTFDatabaseLoader_h
 
 #include "core/platform/audio/HRTFDatabase.h"
-#include <wtf/PassRefPtr.h>
-#include <wtf/RefCounted.h>
-#include <wtf/RefPtr.h>
-#include <wtf/Threading.h>
+#include "wtf/HashMap.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefCounted.h"
+#include "wtf/RefPtr.h"
+#include "wtf/Threading.h"
 
 namespace WebCore {
 
@@ -41,14 +42,12 @@ namespace WebCore {
 
 class HRTFDatabaseLoader : public RefCounted<HRTFDatabaseLoader> {
 public:
-    // Lazily creates the singleton HRTFDatabaseLoader (if not already created) and starts loading asynchronously (when created the first time).
-    // Returns the singleton HRTFDatabaseLoader.
+    // Lazily creates a HRTFDatabaseLoader (if not already created) for the given sample-rate
+    // and starts loading asynchronously (when created the first time).
+    // Returns the HRTFDatabaseLoader.
     // Must be called from the main thread.
     static PassRefPtr<HRTFDatabaseLoader> createAndLoadAsynchronouslyIfNecessary(float sampleRate);
 
-    // Returns the singleton HRTFDatabaseLoader.
-    static HRTFDatabaseLoader* loader() { return s_loader; }
-    
     // Both constructor and destructor must be called from the main thread.
     ~HRTFDatabaseLoader();
     
@@ -65,13 +64,16 @@ public:
     // Called in asynchronous loading thread.
     void load();
 
-    // defaultHRTFDatabase() gives access to the loaded database.
-    // This can be called from any thread, but it is the callers responsibilty to call this while the context (and thus HRTFDatabaseLoader)
-    // is still alive.  Otherwise this will return 0.
-    static HRTFDatabase* defaultHRTFDatabase();
-
     void reportMemoryUsage(MemoryObjectInfo*) const;
 
+    // Map from sample-rate to loader.
+    class LoaderMap : public HashMap<double, HRTFDatabaseLoader*> {
+    public:
+        void reportMemoryUsage(MemoryObjectInfo*) const;
+    };
+
+    static HRTFDatabaseLoader::LoaderMap* loaderMap() { return s_loaderMap; }

[Ken Russell (switch to Gerrit), 2013/05/13 21:44:18]

It seems a bad idea to expose the LoaderMap directly. The methods in this class
which access it assert that they're called on the main thread, but by exposing
the LoaderMap to the outside world, constraints could be violated.

[Chris Rogers, 2013/05/14 20:23:10]

Agreed that it's not ideal, but PlatformMemoryInstrumentation.cpp needs it...

+
 private:
     // Both constructor and destructor must be called from the main thread.
     explicit HRTFDatabaseLoader(float sampleRate);
@@ -80,7 +82,9 @@ private:
     // This must be called from the main thread.
     void loadAsynchronously();
 
-    static HRTFDatabaseLoader* s_loader; // singleton
+    // Keeps track of loaders on a per-sample-rate basis.
+    static LoaderMap* s_loaderMap; // singleton
+
     OwnPtr<HRTFDatabase> m_hrtfDatabase;
 
     // Holding a m_threadLock is required when accessing m_databaseLoaderThread.