Introduce OnceClosure and BindOnce

base/bind.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_BIND_H_
 #define BASE_BIND_H_
 
 #include "base/bind_internal.h"
 
 // -----------------------------------------------------------------------------
 // Usage documentation
 // -----------------------------------------------------------------------------
 //
 // See //docs/callback.md for documentation.
 //
 //
 // -----------------------------------------------------------------------------
 // Implementation notes
 // -----------------------------------------------------------------------------
 //
 // If you're reading the implementation, before proceeding further, you should
 // read the top comment of base/bind_internal.h for a definition of common
 // terms and concepts.
 
 namespace base {
+namespace internal {
 
+// Bind as OnceCallback.
 template <typename Functor, typename... Args>
-inline base::Callback<MakeUnboundRunType<Functor, Args...>> Bind(
-    Functor&& functor,
-    Args&&... args) {
+inline OnceCallback<MakeUnboundRunType<Functor, Args...>>
+BindOnce(Functor&& functor, Args&&... args) {
   using BindState = internal::MakeBindStateType<Functor, Args...>;
   using UnboundRunType = MakeUnboundRunType<Functor, Args...>;
   using Invoker = internal::Invoker<BindState, UnboundRunType>;
-  using CallbackType = Callback<UnboundRunType>;
+  using CallbackType = OnceCallback<UnboundRunType>;
 
   // Store the invoke func into PolymorphicInvoke before casting it to
   // InvokeFuncStorage, so that we can ensure its type matches to
+  // PolymorphicInvoke, to which CallbackType will cast back.
+  using PolymorphicInvoke = typename CallbackType::PolymorphicInvoke;
+  PolymorphicInvoke invoke_func = &Invoker::RunOnce;
+
+  using InvokeFuncStorage = internal::BindStateBase::InvokeFuncStorage;
+  return CallbackType(new BindState(
+      reinterpret_cast<InvokeFuncStorage>(invoke_func),
+      std::forward<Functor>(functor),
+      std::forward<Args>(args)...));
+}
+
+// Bind as RepeatingCallback.
+template <typename Functor, typename... Args>
+inline RepeatingCallback<MakeUnboundRunType<Functor, Args...>>
+BindRepeating(Functor&& functor, Args&&... args) {
+  using BindState = internal::MakeBindStateType<Functor, Args...>;
+  using UnboundRunType = MakeUnboundRunType<Functor, Args...>;
+  using Invoker = internal::Invoker<BindState, UnboundRunType>;
+  using CallbackType = RepeatingCallback<UnboundRunType>;
+
+  // Store the invoke func into PolymorphicInvoke before casting it to
+  // InvokeFuncStorage, so that we can ensure its type matches to
   // PolymorphicInvoke, to which CallbackType will cast back.
   using PolymorphicInvoke = typename CallbackType::PolymorphicInvoke;
   PolymorphicInvoke invoke_func = &Invoker::Run;
 
   using InvokeFuncStorage = internal::BindStateBase::InvokeFuncStorage;
   return CallbackType(new BindState(
       reinterpret_cast<InvokeFuncStorage>(invoke_func),
       std::forward<Functor>(functor),
       std::forward<Args>(args)...));
 }
 
+}  // namespace internal
+
+// Unannotated Bind.
+// TODO(tzik): Deprecate this and migrate to OnceCallback and
+// RepeatingCallback, once they get ready.
+template <typename Functor, typename... Args>
+inline Callback<MakeUnboundRunType<Functor, Args...>>
+Bind(Functor&& functor, Args&&... args) {
+  return internal::BindRepeating(std::forward<Functor>(functor),
+                                 std::forward<Args>(args)...);
+}
+
 }  // namespace base
 
 #endif  // BASE_BIND_H_