monitor/src/misc/Singleton.h

   1 #ifndef AESALON_MISC_SINGLETON_H
   2 #define AESALON_MISC_SINGLETON_H
   3
   4 #include <pthread.h>
   5
   6 #include "Exception.h"
   7
   8 namespace Aesalon {
   9 namespace Misc {
  10
  11 /** Exception class, thrown when a singleton is initialized for the second
  12     time.
  13 */
  14 class MultipleSingletonException : public Exception {
  15 public:
  16     MultipleSingletonException() : Exception("Singleton already initialized") {}
  17 };
  18
  19 /** Exception class, thrown when a singleton instance is requested before the
  20     singleton has been initialized.
  21 */
  22 class UnitializedSingletonException : public Exception {
  23 public:
  24     UnitializedSingletonException() : Exception("Singleton not initialized") {}
  25 };
  26
  27 /** Singleton class, contains a basic singleton implementation. */
  28 template<typename Type>
  29 class Singleton {
  30 private:
  31     /** Singleton instance, declared in each singleton derived class. */
  32     static Type *instance;
  33     /** Singleton multithreading mutex. Makes the singleton class
  34         thread-safe. */
  35     pthread_mutex_t singleton_mutex;
  36
  37     /** Returns the lockable mutex for the current singleton.
  38         @return A lockable mutex, which helps make the singleton library
  39             thread-safe.
  40     */
  41     pthread_mutex_t *get_mutex() { return &singleton_mutex; }
  42 public:
  43     /** Basic constructor, checks if the singleton has been initialized yet.
  44         @throw MultipleSingletonException If the singleton has already been
  45             initialized.
  46     */
  47     Singleton() {
  48         if(instance) throw MultipleSingletonException();
  49         instance = static_cast<Type *>(this);
  50         pthread_mutex_init(&singleton_mutex, NULL);
  51     }
  52
  53     /** Virtual destructor. If the instance is initialized, set the pointer to
  54             zero, so that it can be initialized again if nessasary.
  55     */
  56     virtual ~Singleton() {
  57         if(instance) instance = 0;
  58         pthread_mutex_destroy(&singleton_mutex);
  59     }
  60
  61     /** Static member to return the singleton instance.
  62         @throw UnitializedSingletonException If the instance is not initialized.
  63         @return The singleton instance, as a pointer.
  64     */
  65     static Type *get_instance() {
  66         if(!instance) throw UnitializedSingletonException();
  67         return instance;
  68     }
  69
  70     static void lock_mutex() {
  71         pthread_mutex_lock(get_instance()->get_mutex());
  72     }
  73
  74     static void unlock_mutex() {
  75         pthread_mutex_unlock(get_instance()->get_mutex());
  76     }
  77 };
  78
  79 } // namespace Misc
  80 } // namespace Aesalon
  81
  82 #endif