timer.hpp

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// 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
//
//     http://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

#ifndef __PROCESS_TIMER_HPP__
#define __PROCESS_TIMER_HPP__

#include <stdint.h>
#include <stdlib.h> // For abort.

#include <process/pid.hpp>
#include <process/timeout.hpp>

#include <stout/duration.hpp>
#include <stout/lambda.hpp>

namespace process {

// Timer represents a delayed thunk, that can get created (scheduled)
// and canceled using the Clock.

class Timer
{
public:
  Timer() : id(0), pid(process::UPID()), thunk(&abort) {}

  bool operator==(const Timer& that) const
  {
    return id == that.id;
  }

  // Invokes this timer's thunk.
  void operator()() const
  {
    thunk();
  }

  // Returns the timeout associated with this timer.
  Timeout timeout() const
  {
    return t;
  }

  // Returns the PID of the running process when this timer was
  // created (via timers::create) or an empty PID if no process was
  // running when this timer was created.
  process::UPID creator() const
  {
    return pid;
  }

private:
  friend class Clock;

  Timer(uint64_t _id,
        const Timeout& _t,
        const process::UPID& _pid,
        const lambda::function<void()>& _thunk)
    : id(_id), t(_t), pid(_pid), thunk(_thunk)
  {}

  uint64_t id; // Used for equality.

  Timeout t;

  // We store the PID of the "issuing" (i.e., "running") process (if
  // there is one). We don't store a pointer to the process because we
  // can't dereference it since it might no longer be valid. (Instead,
  // the PID can be used internally to check if the process is still
  // valid and get a reference to it.)
  process::UPID pid;

  lambda::function<void()> thunk;
};

} // namespace process {

#endif // __PROCESS_TIMER_HPP__