future.h

Go to the documentation of this file.

#ifndef CVMFS_UTIL_FUTURE_H_
#define CVMFS_UTIL_FUTURE_H_

#include <pthread.h>

#include <cassert>

#include "util/mutex.h"
#include "util/single_copy.h"

#ifdef CVMFS_NAMESPACE_GUARD
namespace CVMFS_NAMESPACE_GUARD {
#endif

template <typename T>
class Future : SingleCopy {
 public:
  Future() : object_was_set_(false) {
    int retval = pthread_mutex_init(&mutex_, NULL);
    assert(retval == 0);
    retval = pthread_cond_init(&object_set_, NULL);
    assert(retval == 0);
  }

  ~Future() {
    int retval = pthread_cond_destroy(&object_set_);
    assert(retval == 0);
    retval = pthread_mutex_destroy(&mutex_);
    assert(retval == 0);
  }

  void Set(const T &object) {
    MutexLockGuard guard(mutex_);
    assert(!object_was_set_);
    object_ = object;
    object_was_set_ = true;
    pthread_cond_broadcast(&object_set_);
  }

  T& Get() {
    Wait();
    return object_;
  }

  const T& Get() const {
    Wait();
    return object_;
  }

 private:
  void Wait() const {
    MutexLockGuard guard(mutex_);
    while (!object_was_set_) {
      pthread_cond_wait(&object_set_, &mutex_);
    }
  }

  T object_;
  mutable pthread_mutex_t mutex_;
  mutable pthread_cond_t object_set_;
  bool object_was_set_;
};

#ifdef CVMFS_NAMESPACE_GUARD
}  // namespace CVMFS_NAMESPACE_GUARD
#endif

#endif  // CVMFS_UTIL_FUTURE_H_