task_runner.cpp

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// Copyright 2024 Arthur Sonzogni. All rights reserved.
// Use of this source code is governed by the MIT license that can be found in
// the LICENSE file.
#include "ftxui/component/task_runner.hpp"
 
#include <cassert>
#include <thread>
 
namespace ftxui::task {
 
static thread_local TaskRunner* current_task_runner = nullptr;  // NOLINT
 
TaskRunner::TaskRunner() {
  assert(!previous_task_runner_);
  previous_task_runner_ = current_task_runner;
  current_task_runner = this;
}
 
TaskRunner::~TaskRunner() {
  current_task_runner = previous_task_runner_;
}
 
// static
auto TaskRunner::Current() -> TaskRunner* {
  assert(current_task_runner);
  return current_task_runner;
}
 
auto TaskRunner::PostTask(Task task) -> void {
  queue_.PostTask(PendingTask{std::move(task)});
}
 
auto TaskRunner::PostDelayedTask(Task task,
                                 std::chrono::steady_clock::duration duration)
    -> void {
  queue_.PostTask(PendingTask{std::move(task), duration});
}
 
/// 執行佇列中的 task。
auto TaskRunner::RunUntilIdle()
    -> std::optional<std::chrono::steady_clock::duration> {
  while (true) {
    auto maybe_task = queue_.Get();
    if (std::holds_alternative<std::monostate>(maybe_task)) {
      // 沒有更多的 task 可執行，結束迴圈。
      return std::nullopt;
    }
 
    if (std::holds_alternative<Task>(maybe_task)) {
      executed_tasks_++;
      std::get<Task>(maybe_task)();
      continue;
    }
 
    if (std::holds_alternative<std::chrono::steady_clock::duration>(
            maybe_task)) {
      return std::get<std::chrono::steady_clock::duration>(maybe_task);
    }
  }
}
 
auto TaskRunner::Run() -> void {
  while (true) {
    auto duration = RunUntilIdle();
    if (!duration) {
      // 沒有更多的 task 可執行，結束迴圈。
      return;
    }
 
    // 睡眠，直到下一個 task 可以執行的時間為止。
    std::this_thread::sleep_for(duration.value());
  }
}
 
}  // namespace ftxui::task