libcxx/test/support/counting_projection.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef TEST_SUPPORT_COUNTING_PROJECTION_H
  10 #define TEST_SUPPORT_COUNTING_PROJECTION_H
  11
  12 #include <functional>
  13 #include <utility>
  14 #include "test_macros.h"
  15
  16 #if TEST_STD_VER > 14
  17
  18 template <class Proj = std::identity>
  19 class counting_projection {
  20   Proj proj_;
  21   int* count_ = nullptr;
  22
  23 public:
  24   constexpr counting_projection() = default;
  25   constexpr counting_projection(int& count) : count_(&count) {}
  26   constexpr counting_projection(Proj proj, int& count) : proj_(std::move(proj)), count_(&count) {}
  27
  28   template <class T>
  29   constexpr decltype(auto) operator()(T && value) const {
  30     ++(*count_);
  31     return std::invoke(proj_, std::forward<T>(value));
  32   }
  33 };
  34
  35 counting_projection(int& count) -> counting_projection<std::identity>;
  36 template <class Proj>
  37 counting_projection(Proj proj, int& count) -> counting_projection<Proj>;
  38
  39 #endif // TEST_STD_VER > 14
  40
  41 #endif // TEST_SUPPORT_COUNTING_PROJECTION_H