Add helpers for CGL types.

base/mac/scoped_typeref.h

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.

[Avi (use Gerrit), 2014/02/07 01:45:29]

no (c)

[ccameron, 2014/02/07 06:57:49]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_MAC_SCOPED_TYPEREF_H_
+#define BASE_MAC_SCOPED_TYPEREF_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/memory/scoped_policy.h"
+
+namespace base {
+
+// ScopedTypeRef<> is a generalized form of ScopedCFTypeRef<>, for use with

[Avi (use Gerrit), 2014/02/07 01:45:29]

OTOH, you could look at ScopedCFTypeRef as being a specialized form of
ScopedTypeRef. If we went this route, I'd like to see some relationship between
them, perhaps even just a typedef of ScopedCFTypeRef as being a partial
specialization of ScopedTypeRef with CFRetain/Release.

Especially since there's massive duplication here.

[ccameron, 2014/02/07 06:57:49]

Good call. Change ScopedCFTypeRef to be a subclass.

+// types that have have type-specific retain and release functions (e.g,
+// CGLContextObj, which requires use of CGLReleaseContext instead of CFRelease).
+//
+// This type may be initialized in the same ways as ScopedCFTypeRef<>, with
+// parameterized ownership.
+//
+// Additionally, for the many types that have pass-by-pointer constructor
+// functions, the operator& is overloaded, to allow direct initialization
+// and assumption of ownership of the object, e.g:
+//
+//     base::ScopedTypeRef<CGLContextObj, CGLRetainContext, CGLReleaseContext>
+//         context;
+//     CGLCreateContext(pixel_format, share_group, &context);
+
+template<typename T, T Retain(T), void Release(T)>
+class ScopedTypeRef {
+ public:
+  typedef T element_type;
+
+  ScopedTypeRef() : object_(NULL) {}
+
+  explicit ScopedTypeRef(
+      T object,
+      base::scoped_policy::OwnershipPolicy policy)
+      : object_(object) {
+    if (object_ && policy == base::scoped_policy::RETAIN)
+      Retain(object_);
+  }
+
+  ScopedTypeRef(const ScopedTypeRef<T, Retain, Release>& that)
+      : object_(that.object_) {
+    if (object_)
+      Retain(object_);
+  }
+
+  ~ScopedTypeRef() {
+    if (object_)
+      Release(object_);
+  }
+
+  // This is to be used only to take ownership of objects that are created
+  // by pass-by-pointer constructor functions. To enforce this, require that
+  // the object be reset to NULL before this may be used.
+  T* operator&() WARN_UNUSED_RESULT {
+    DCHECK(!object_);
+    return &object_;
+  }
+
+  ScopedTypeRef& operator=(const ScopedTypeRef<T, Retain, Release>& that) {
+    reset(that.get(), base::scoped_policy::RETAIN);
+    return *this;
+  }
+
+  void reset(T object = NULL,
+             base::scoped_policy::OwnershipPolicy policy =
+                base::scoped_policy::ASSUME) {
+    if (object && policy == base::scoped_policy::RETAIN)
+      Retain(object);
+    if (object_)
+      Release(object_);
+    object_ = object;
+  }
+
+  bool operator==(T that) const {
+    return object_ == that;
+  }
+
+  bool operator!=(T that) const {
+    return object_ != that;
+  }
+
+  operator T() const {
+    return object_;
+  }
+
+  T get() const {
+    return object_;
+  }
+
+  void swap(ScopedTypeRef& that) {
+    T temp = that.object_;
+    that.object_ = object_;
+    object_ = temp;
+  }
+
+  // ScopedTypeRef<>::release() is like scoped_ptr<>::release.  It is NOT
+  // a wrapper for Release().  To force a ScopedTypeRef<> object to call
+  // Release(), use ScopedTypeRef<>::reset().
+  T release() WARN_UNUSED_RESULT {
+    T temp = object_;
+    object_ = NULL;
+    return temp;
+  }
+
+ private:
+  T object_;
+};
+
+}  // namespace base
+
+#endif  // BASE_MAC_SCOPED_TYPEREF_H_