wyonce.h

一个不错

/* Copyright is licensed under GNU LGPL.                 by I.J.Wang 2003
*/

#ifndef WYONCE_H__
#define WYONCE_H__
#define WYONCE_VERSION 31

#include "wyret.h"     // include libwy base definitions
#include <pthread.h>

/*
  WyOnce defines the object that ensures the only member function once(...)
  calls the given paramter function at most once.
*/
class WyOnce {
  public:
    //
    // [Syn] Construct default object
    //
    inline WyOnce() WY__TSPC()
	  :_ovar(DefaultValue) {};
    
    //
    // [Syn] Construct object and call the given parameter function immedicately.
    //
    // Note: If object is declared auto, static modifier may be required.
    //
    // [Throw]
    //
    explicit  // no implicit conversion
    inline WyOnce( void(*once_func)(void) )
	      :_ovar(DefaultValue) { once(once_func); };

    //
    // [Syn] Is object the same as that of default constructed state.
    //
    // [Ret] true = object is the same as default constructed state.
    //       false= otherwise
    //
    bool is_default(void) const WY__TSPC()
              { return _ovar==DefaultValue; };

    //
    // [Syn] Call the parameter function at most once.
    //       This function moves object away from the default state
    //
    // [Throw]
    //
    void once( void(*once_func)(void) );

  private:
    static const ::pthread_once_t DefaultValue=PTHREAD_ONCE_INIT;
    ::pthread_once_t _ovar;

    WyOnce(const WyOnce&) WY__TSPC(); // not to use
    const WyOnce& operator=(const WyOnce&) WY__TSPC(); // not to use
    bool operator==(const WyOnce&) WY__TSPC(); // not to use
};

#endif