SkLazyPtr suitable as a local or class member.

src/core/SkLazyPtr.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLazyPtr_DEFINED
 #define SkLazyPtr_DEFINED
 
-/** Declare a lazily-chosen static pointer (or array of pointers) of type F.
+/** Declare a lazily-chosen static pointer (or array of pointers) of type T.
  *
  *  Example usage:
  *
  *  Foo* GetSingletonFoo() {
  *      SK_DECLARE_STATIC_LAZY_PTR(Foo, singleton);  // Created with SkNEW, destroyed with SkDELETE.
  *      return singleton.get();
  *  }
  *
  *  These macros take an optional T* (*Create)() and void (*Destroy)(T*) at the end.
  *  If not given, we'll use SkNEW and SkDELETE.
@@ skipping 20 matching lines @@
  *  You can think of SK_DECLARE_STATIC_LAZY_PTR as a cheaper specialization of
  *  SkOnce.  There is no mutex or extra storage used past the pointer itself.
  *
  *  We may call Create more than once, but all threads will see the same pointer
  *  returned from get().  Any extra calls to Create will be cleaned up.
  *
  *  These macros must be used in a global scope, not in function scope or as a class member.
  */
 
 #define SK_DECLARE_STATIC_LAZY_PTR(T, name, ...) \
-    namespace {} static Private::SkLazyPtr<T, ##__VA_ARGS__> name
+    namespace {} static Private::SkLazyPtrBase<T, ##__VA_ARGS__> name
 
 #define SK_DECLARE_STATIC_LAZY_PTR_ARRAY(T, name, N, ...) \
     namespace {} static Private::SkLazyPtrArray<T, N, ##__VA_ARGS__> name
 
 // namespace {} forces these macros to only be legal in global scopes.  Chrome has thread-safety
 // problems with them in function-local statics because it uses -fno-threadsafe-statics, and even
 // in builds with threadsafe statics, those threadsafe statics are just unnecessary overhead.
 
-
 // Everything below here is private implementation details.  Don't touch, don't even look.
 
 #include "SkDynamicAnnotations.h"
 #include "SkThread.h"
 #include "SkThreadPriv.h"
 
 // See FIXME below.
 class SkFontConfigInterfaceDirect;
 
 namespace Private {
@@ skipping 24 matching lines @@
 // _through_ our atomically set pointer, there is a data dependency between our
 // atomic and the guarded data, and so we only need writer-releases /
 // reader-consumes memory pairing rather than the more general write-releases /
 // reader-acquires convention.
 //
 // This is nice, because a sk_consume_load is free on all our platforms: x86,
 // ARM, MIPS.  In contrast, sk_acquire_load issues a memory barrier on non-x86.
 
 // This has no constructor and must be zero-initalized (the macro above does this).
 template <typename T, T* (*Create)() = sk_new<T>, void (*Destroy)(T*) = sk_delete<T> >
-class SkLazyPtr {
+class SkLazyPtrBase {
 public:
     T* get() {
         // If fPtr has already been filled, we need a consume barrier when loading it.
         // If not, we need a release barrier when setting it.  try_cas will do that.
         T* ptr = (T*)sk_consume_load(&fPtr);
         return ptr ? ptr : try_cas<T*, Destroy>(&fPtr, Create());
     }
 
-private:
+protected:
     void* fPtr;
 };
 
 template <typename T> T* sk_new_arg(int i) { return SkNEW_ARGS(T, (i)); }
 
 // This has no constructor and must be zero-initalized (the macro above does this).
 template <typename T, int N, T* (*Create)(int) = sk_new_arg<T>, void (*Destroy)(T*) = sk_delete<T> >
 class SkLazyPtrArray {
 public:
     T* operator[](int i) {
         SkASSERT(i >= 0 && i < N);
         // If fPtr has already been filled, we need an consume barrier when loading it.
         // If not, we need a release barrier when setting it.  try_cas will do that.
         T* ptr = (T*)sk_consume_load(&fArray[i]);
         return ptr ? ptr : try_cas<T*, Destroy>(&fArray[i], Create(i));
     }
 
 private:
     void* fArray[N];
 };
 
 }  // namespace Private
 
+// This version is suitable for use as a class member.
+// It's the same as above except it has a constructor to zero itself and a destructor to clean up.
+template <typename T,
+          T* (*Create)() = Private::sk_new<T>,
+          void (*Destroy)(T*) = Private::sk_delete<T> >
+class SkLazyPtr : public Private::SkLazyPtrBase<T, Create, Destroy> {
+public:
+    SkLazyPtr() { INHERITED::fPtr = NULL; }
+    ~SkLazyPtr() { if (INHERITED::fPtr) { Destroy((T*)INHERITED::fPtr); } }
+private:
+    typedef Private::SkLazyPtrBase<T, Create, Destroy> INHERITED;
+};
+
+
 #endif//SkLazyPtr_DEFINED