func_task.h

// Copyright 2023 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
 
#include <optional>
#include <type_traits>
 
#include "pw_async2/task.h"
#include "pw_function/function.h"
 
namespace pw::async2 {
 
 
template <typename Func = Function<Poll<>(Context&)>>
class FuncTask final : public Task {
 public:
  template <typename F>
  explicit constexpr FuncTask(F&& func) : func_(std::forward<F>(func)) {}
 
  FuncTask(const FuncTask&) = delete;
  FuncTask& operator=(const FuncTask&) = delete;
 
  FuncTask(FuncTask&&) = delete;
  FuncTask& operator=(FuncTask&&) = delete;
 
  ~FuncTask() override { Deregister(); }
 
 private:
  Poll<> DoPend(Context& cx) override { return func_(cx); }
 
  Func func_;
};
 
template <typename Func>
FuncTask(Func&&) -> FuncTask<std::decay_t<Func>>;
 
enum class ReturnValuePolicy : bool { kKeep, kDiscard };
 
template <typename Func = Function<Poll<>()>,
          ReturnValuePolicy = std::is_void_v<std::invoke_result_t<Func>>
                                  ? ReturnValuePolicy::kDiscard
                                  : ReturnValuePolicy::kKeep>
class RunOnceTask final : public Task {
 public:
  using value_type =
      std::conditional_t<std::is_void_v<std::invoke_result_t<Func>>,
                         ReadyType,
                         std::invoke_result_t<Func>>;
 
  explicit constexpr RunOnceTask(Func&& func)
      : func_(std::forward<Func>(func)) {}
 
  RunOnceTask(const RunOnceTask&) = delete;
  RunOnceTask& operator=(const RunOnceTask&) = delete;
 
  RunOnceTask(RunOnceTask&&) = delete;
  RunOnceTask& operator=(RunOnceTask&&) = delete;
 
  ~RunOnceTask() override { Deregister(); }
 
  bool has_value() const { return return_value_.has_value(); }
 
  value_type& value() { return return_value_.value(); }
 
  const value_type& value() const { return return_value_.value(); }
 
  value_type& Wait() {
    Task::Join();
    return *return_value_;
  }
 
 private:
  Poll<> DoPend(Context&) override {
    if constexpr (std::is_void_v<std::invoke_result_t<Func>>) {
      func_();
      return_value_.emplace();
    } else {
      return_value_ = func_();
    }
    return Ready();
  }
 
  Func func_;
  std::optional<value_type> return_value_;
};
 
template <typename Func>
class RunOnceTask<Func, ReturnValuePolicy::kDiscard> final : public Task {
 public:
  explicit constexpr RunOnceTask(Func&& func)
      : func_(std::forward<Func>(func)) {}
 
  RunOnceTask(const RunOnceTask&) = delete;
  RunOnceTask& operator=(const RunOnceTask&) = delete;
 
  RunOnceTask(RunOnceTask&&) = delete;
  RunOnceTask& operator=(RunOnceTask&&) = delete;
 
  ~RunOnceTask() override { Deregister(); }
 
 private:
  Poll<> DoPend(Context&) override {
    (void)func_();
    return Ready();
  }
 
  Func func_;
};
 
template <typename Func>
RunOnceTask(Func&&) -> RunOnceTask<Func>;
 
 
}  // namespace pw::async2