Implements remaining SecurityContext calls for iOS

runtime/bin/reference_counting.h

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef BIN_REFERENCE_COUNTING_H_
+#define BIN_REFERENCE_COUNTING_H_
+
+#include "vm/atomic.h"
+
+namespace dart {
+namespace bin {
+
+// Inherit from this class where instances of the derived class should be
+// reference counted. Reference counts on instances are incremented and
+// decremented explicitly with calls to Retain() and Release(). E.g.:
+//
+// class Foo : public ReferenceCounted<Foo> {
+//  public:
+//   Foo() : ReferenceCounted() {}
+//   ...
+// };
+//
+// void DoStuffWithAFoo() {
+//   Foo* foo = new Foo();
+//   foo->Retain();
+//   ...
+//   foo->Release();
+// }
+template <class Derived>
+class ReferenceCounted {
+ public:
+  ReferenceCounted() :
+    ref_count_(0) {
+  }
+
+  ~ReferenceCounted() {
+    ASSERT(ref_count_ == 0);
+  }
+
+  void Retain() {
+    uintptr_t old = AtomicOperations::FetchAndIncrement(&ref_count_);
+    ASSERT(old >= 0);
+  }
+
+  void Release() {
+    uintptr_t old = AtomicOperations::FetchAndDecrement(&ref_count_);
+    ASSERT(old > 0);
+    if (old == 1) {
+      delete reinterpret_cast<Derived*>(this);
+    }
+  }
+
+ private:
+  uintptr_t ref_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReferenceCounted);
+};
+
+// Creates a scope at the end of which, a reference counted object is
+// Released. This is useful for reference counted objects recieved by the IO
+// Service, which have already been Retained E.g.:
+//
+// CObject* Foo::FooRequest(const CObjectArray& request) {
+//   Foo* foo = CObjectToFoo(request[0]);
+//   RefCntReleaseScope<Foo> rs(foo);
+//   ...
+// }
+template <class Target>
+class RefCntReleaseScope {
+ public:
+  explicit RefCntReleaseScope(ReferenceCounted<Target>* t) : target_(t) {
+    ASSERT(target_ != NULL);

[Ivan Posva, 2016/04/08 13:18:21]

ASSERT that ref_count_ is greater than 1?

[zra, 2016/04/08 16:07:48]

Done.

+  }
+  ~RefCntReleaseScope() {
+    target_->Release();
+  }
+
+ private:
+  ReferenceCounted<Target>* target_;
+
+  DISALLOW_ALLOCATION();
+  DISALLOW_COPY_AND_ASSIGN(RefCntReleaseScope);
+};
+
+template <class Target>

[Ivan Posva, 2016/04/08 13:18:21]

There is good documentation for the above classes, which seems to be missing
from here. Can you please add it, as it is hard to understand the purpose of
this class otherwise.

[zra, 2016/04/08 16:07:48]

Done.

+class RetainedPointer {
+ public:
+  RetainedPointer() : target_(NULL) {}
+
+  explicit RetainedPointer(ReferenceCounted<Target>* t) : target_(t) {
+    if (target_ != NULL) {
+      target_->Retain();
+    }
+  }
+
+  ~RetainedPointer() {
+    if (target_ != NULL) {
+      target_->Release();
+    }
+  }
+
+  void set(ReferenceCounted<Target>* t) {
+    if (target_ != NULL) {
+      target_->Release();
+    }
+    target_ = t;
+    if (target_ != NULL) {
+      target_->Retain();
+    }
+  }
+
+  Target* get() const {
+    return reinterpret_cast<Target*>(target_);
+  }
+
+ private:
+  ReferenceCounted<Target>* target_;
+
+  DISALLOW_ALLOCATION();
+  DISALLOW_COPY_AND_ASSIGN(RetainedPointer);
+};
+
+}  // namespace bin
+}  // namespace dart
+
+#endif  // BIN_REFERENCE_COUNTING_H_