Add a 'unique' method to SkRefCnt, document the usage, and add support.

include/core/SkRefCnt.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkRefCnt_DEFINED
@@ skipping 23 matching lines @@
 
     /** Destruct, asserting that the reference count is 1.
     */
     virtual ~SkRefCnt() {
 #ifdef SK_DEBUG
         SkASSERT(fRefCnt == 1);
         fRefCnt = 0;    // illegal value, to catch us if we reuse after delete
 #endif
     }
 
-    /** Return the reference count.
-    */
+    /** Return the reference count. Use only for debugging. */
     int32_t getRefCnt() const { return fRefCnt; }
 
+    /** Returns true if the caller is the only owner.
+     *  Ensures that all previous owner's actions are complete.
+     */
+    bool unique() const {
+        bool const unique = (1 == fRefCnt);
+        if (unique) {
+            // Aquire barrier (L/SL), if not provided by load of fRefCnt.
+            // Prevents user's 'unique' code from happening before decrements.
+            //TODO: issue the barrier.
+        }
+        return unique;
+    }
+
     /** Increment the reference count. Must be balanced by a call to unref().
     */
     void ref() const {
         SkASSERT(fRefCnt > 0);
         sk_atomic_inc(&fRefCnt);  // No barrier required.
     }
 
     /** Decrement the reference count. If the reference count is 1 before the
         decrement, then delete the object. Note that if this is the case, then
         the object needs to have been allocated via new, and not on the stack.
     */
     void unref() const {
         SkASSERT(fRefCnt > 0);
         // Release barrier (SL/S), if not provided below.
         if (sk_atomic_dec(&fRefCnt) == 1) {
             // Aquire barrier (L/SL), if not provided above.
             // Prevents code in dispose from happening before the decrement.
             sk_membar_aquire__after_atomic_dec();
             internal_dispose();
         }
     }
 
     void validate() const {
         SkASSERT(fRefCnt > 0);
     }
 
     /**
-     *  Alias for ref(), for compatibility with scoped_refptr.
-     */
-    void AddRef() { this->ref(); }
-
-    /**
-     *  Alias for unref(), for compatibility with scoped_refptr.
-     */
-    void Release() { this->unref(); }
-
-    /**
      * Alias for unref(), for compatibility with WTF::RefPtr.
      */
     void deref() { this->unref(); }
 
 protected:
     /**
      *  Allow subclasses to call this if they've overridden internal_dispose
      *  so they can reset fRefCnt before the destructor is called. Should only
      *  be called right before calling through to inherited internal_dispose()
      *  or before calling the destructor.
      */
     void internal_dispose_restore_refcnt_to_1() const {
 #ifdef SK_DEBUG
         SkASSERT(0 == fRefCnt);
         fRefCnt = 1;
 #endif
     }
 
 private:
     /**
      *  Called when the ref count goes to 0.
      */
     virtual void internal_dispose() const {
         this->internal_dispose_restore_refcnt_to_1();
         SkDELETE(this);
     }
 
+    // The following friends are those which override internal_dispose()
+    // and conditionally call SkRefCnt::internal_dispose().
+    friend class GrTexture;
     friend class SkWeakRefCnt;
-    friend class GrTexture;     // to allow GrTexture's internal_dispose to
-                                // call SkRefCnt's & directly set fRefCnt (to 1)
 
     mutable int32_t fRefCnt;
 
     typedef SkNoncopyable INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /** Helper macro to safely assign one SkRefCnt[TS]* to another, checking for
     null in on each side of the assignment, and ensuring that ref() is called
@@ skipping 137 matching lines @@
     typedef T* SkRefPtr::*unspecified_bool_type;
     operator unspecified_bool_type() const {
         return fObj ? &SkRefPtr::fObj : NULL;
     }
 
 private:
     T* fObj;
 };
 
 #endif