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      1 // Copyright 2014 The Chromium OS Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef LIBBRILLO_BRILLO_BIND_LAMBDA_H_
      6 #define LIBBRILLO_BRILLO_BIND_LAMBDA_H_
      7 
      8 #include <base/bind.h>
      9 
     10 ////////////////////////////////////////////////////////////////////////////////
     11 // This file is an extension to base/bind_internal.h and adds a RunnableAdapter
     12 // class specialization that wraps a functor (including lambda objects), so
     13 // they can be used in base::Callback/base::Bind constructs.
     14 // By including this file you will gain the ability to write expressions like:
     15 //    base::Callback<int(int)> callback = base::Bind([](int value) {
     16 //      return value * value;
     17 //    });
     18 ////////////////////////////////////////////////////////////////////////////////
     19 namespace base {
     20 namespace internal {
     21 
     22 // LambdaAdapter is a helper class that specializes on different function call
     23 // signatures and provides the RunType and Run() method required by
     24 // RunnableAdapter<> class.
     25 template <typename Lambda, typename Sig>
     26 class LambdaAdapter;
     27 
     28 // R(...)
     29 template <typename Lambda, typename R, typename... Args>
     30 class LambdaAdapter<Lambda, R(Lambda::*)(Args... args)> {
     31  public:
     32   typedef R(RunType)(Args...);
     33   explicit LambdaAdapter(Lambda lambda) : lambda_(lambda) {}
     34   R Run(Args... args) { return lambda_(std::forward<Args>(args)...); }
     35 
     36  private:
     37   Lambda lambda_;
     38 };
     39 
     40 // R(...) const
     41 template <typename Lambda, typename R, typename... Args>
     42 class LambdaAdapter<Lambda, R(Lambda::*)(Args... args) const> {
     43  public:
     44   typedef R(RunType)(Args...);
     45   explicit LambdaAdapter(Lambda lambda) : lambda_(lambda) {}
     46   R Run(Args... args) { return lambda_(std::forward<Args>(args)...); }
     47 
     48  private:
     49   Lambda lambda_;
     50 };
     51 
     52 template <typename Lambda>
     53 class RunnableAdapter
     54     : public LambdaAdapter<Lambda, decltype(&Lambda::operator())> {
     55  public:
     56   explicit RunnableAdapter(Lambda lambda)
     57       : LambdaAdapter<Lambda, decltype(&Lambda::operator())>(lambda) {}
     58 };
     59 
     60 }  // namespace internal
     61 }  // namespace base
     62 
     63 #endif  // LIBBRILLO_BRILLO_BIND_LAMBDA_H_
     64