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## Class named_upgradable_mutex

boost::interprocess::named_upgradable_mutex

## Synopsis

    // In header: <boost/interprocess/sync/named_upgradable_mutex.hpp>

    class named_upgradable_mutex {
    public:
      // construct/copy/destruct
      named_upgradable_mutex(create_only_t, const char *,
                             const permissions & = permissions());
      named_upgradable_mutex(open_or_create_t, const char *,
                             const permissions & = permissions());
      named_upgradable_mutex(open_only_t, const char *);
      ~named_upgradable_mutex();

      // public member functions
      void lock();
      bool try_lock();
      bool timed_lock(const boost::posix_time::ptime &);
      void unlock();
      void lock_sharable();
      bool try_lock_sharable();
      bool timed_lock_sharable(const boost::posix_time::ptime &);
      void unlock_sharable();
      void lock_upgradable();
      bool try_lock_upgradable();
      bool timed_lock_upgradable(const boost::posix_time::ptime &);
      void unlock_upgradable();
      void unlock_and_lock_upgradable();
      void unlock_and_lock_sharable();
      void unlock_upgradable_and_lock_sharable();
      void unlock_upgradable_and_lock();
      bool try_unlock_upgradable_and_lock();
      bool timed_unlock_upgradable_and_lock(const boost::posix_time::ptime &);
      bool try_unlock_sharable_and_lock();
      bool try_unlock_sharable_and_lock_upgradable();

      // public static functions
      static bool remove(const char *);
    };

## Description

A upgradable mutex with a global name, so it can be found from different processes. This mutex can't be placed in shared memory, and each process should have it's own named upgradable mutex.

### `named_upgradable_mutex` public construct/copy/destruct

1.     named_upgradable_mutex(create_only_t create_only, const char * name,
                              const permissions & perm = permissions());

   Creates a global upgradable mutex with a name. If the upgradable mutex can't be created throws `interprocess_exception`

2.     named_upgradable_mutex(open_or_create_t open_or_create, const char * name,
                              const permissions & perm = permissions());

   Opens or creates a global upgradable mutex with a name, and an initial count. If the upgradable mutex is created, this call is equivalent to `named_upgradable_mutex`(`create_only_t`, ...) If the upgradable mutex is already created, this call is equivalent to `named_upgradable_mutex`(`open_only_t`, ... ).

3.     named_upgradable_mutex(open_only_t open_only, const char * name);

   Opens a global upgradable mutex with a name if that upgradable mutex is previously. created. If it is not previously created this function throws `interprocess_exception`.

4.     ~named_upgradable_mutex();

   Destroys *this and indicates that the calling process is finished using the resource. The destructor function will deallocate any system resources allocated by the system for use by this process for this resource. The resource can still be opened again calling the open constructor overload. To erase the resource from the system use remove().

### `named_upgradable_mutex` public member functions

1.     void lock();

   Effects: The calling thread tries to obtain exclusive ownership of the mutex, and if another thread has exclusive, sharable or upgradable ownership of the mutex, it waits until it can obtain the ownership. Throws: `interprocess_exception` on error.

2.     bool try_lock();

   Effects: The calling thread tries to acquire exclusive ownership of the mutex without waiting. If no other thread has exclusive, sharable or upgradable ownership of the mutex this succeeds. Returns: If it can acquire exclusive ownership immediately returns true. If it has to wait, returns false. Throws: `interprocess_exception` on error.

3.     bool timed_lock(const boost::posix_time::ptime & abs_time);

   Effects: The calling thread tries to acquire exclusive ownership of the mutex waiting if necessary until no other thread has exclusive, sharable or upgradable ownership of the mutex or abs_time is reached. Returns: If acquires exclusive ownership, returns true. Otherwise returns false. Throws: `interprocess_exception` on error.

4.     void unlock();

   Precondition: The thread must have exclusive ownership of the mutex. Effects: The calling thread releases the exclusive ownership of the mutex. Throws: An exception derived from `interprocess_exception` on error.

5.     void lock_sharable();

   Effects: The calling thread tries to obtain sharable ownership of the mutex, and if another thread has exclusive ownership of the mutex, waits until it can obtain the ownership. Throws: `interprocess_exception` on error.

6.     bool try_lock_sharable();

   Effects: The calling thread tries to acquire sharable ownership of the mutex without waiting. If no other thread has exclusive ownership of the mutex this succeeds. Returns: If it can acquire sharable ownership immediately returns true. If it has to wait, returns false. Throws: `interprocess_exception` on error.

7.     bool timed_lock_sharable(const boost::posix_time::ptime & abs_time);

   Effects: The calling thread tries to acquire sharable ownership of the mutex waiting if necessary until no other thread has exclusive ownership of the mutex or abs_time is reached. Returns: If acquires sharable ownership, returns true. Otherwise returns false. Throws: `interprocess_exception` on error.

8.     void unlock_sharable();

   Precondition: The thread must have sharable ownership of the mutex. Effects: The calling thread releases the sharable ownership of the mutex. Throws: An exception derived from `interprocess_exception` on error.

9.     void lock_upgradable();

   Effects: The calling thread tries to obtain upgradable ownership of the mutex, and if another thread has exclusive or upgradable ownership of the mutex, waits until it can obtain the ownership. Throws: `interprocess_exception` on error.

10.     bool try_lock_upgradable();

    Effects: The calling thread tries to acquire upgradable ownership of the mutex without waiting. If no other thread has exclusive or upgradable ownership of the mutex this succeeds. Returns: If it can acquire upgradable ownership immediately returns true. If it has to wait, returns false. Throws: `interprocess_exception` on error.

11.     bool timed_lock_upgradable(const boost::posix_time::ptime & abs_time);

    Effects: The calling thread tries to acquire upgradable ownership of the mutex waiting if necessary until no other thread has exclusive or upgradable ownership of the mutex or abs_time is reached. Returns: If acquires upgradable ownership, returns true. Otherwise returns false. Throws: `interprocess_exception` on error.

12.     void unlock_upgradable();

    Precondition: The thread must have upgradable ownership of the mutex. Effects: The calling thread releases the upgradable ownership of the mutex. Throws: An exception derived from `interprocess_exception` on error.

13.     void unlock_and_lock_upgradable();

    Precondition: The thread must have exclusive ownership of the mutex. Effects: The thread atomically releases exclusive ownership and acquires upgradable ownership. This operation is non-blocking. Throws: An exception derived from `interprocess_exception` on error.

14.     void unlock_and_lock_sharable();

    Precondition: The thread must have exclusive ownership of the mutex. Effects: The thread atomically releases exclusive ownership and acquires sharable ownership. This operation is non-blocking. Throws: An exception derived from `interprocess_exception` on error.

15.     void unlock_upgradable_and_lock_sharable();

    Precondition: The thread must have upgradable ownership of the mutex. Effects: The thread atomically releases upgradable ownership and acquires sharable ownership. This operation is non-blocking. Throws: An exception derived from `interprocess_exception` on error.

16.     void unlock_upgradable_and_lock();

    Precondition: The thread must have upgradable ownership of the mutex. Effects: The thread atomically releases upgradable ownership and acquires exclusive ownership. This operation will block until all threads with sharable ownership release it. Throws: An exception derived from `interprocess_exception` on error.

17.     bool try_unlock_upgradable_and_lock();

    Precondition: The thread must have upgradable ownership of the mutex. Effects: The thread atomically releases upgradable ownership and tries to acquire exclusive ownership. This operation will fail if there are threads with sharable ownership, but it will maintain upgradable ownership. Returns: If acquires exclusive ownership, returns true. Otherwise returns false. Throws: An exception derived from `interprocess_exception` on error.

18.     bool timed_unlock_upgradable_and_lock(const boost::posix_time::ptime & abs_time);

    Precondition: The thread must have upgradable ownership of the mutex. Effects: The thread atomically releases upgradable ownership and tries to acquire exclusive ownership, waiting if necessary until abs_time. This operation will fail if there are threads with sharable ownership or timeout reaches, but it will maintain upgradable ownership. Returns: If acquires exclusive ownership, returns true. Otherwise returns false. Throws: An exception derived from `interprocess_exception` on error.

19.     bool try_unlock_sharable_and_lock();

    Precondition: The thread must have sharable ownership of the mutex. Effects: The thread atomically releases sharable ownership and tries to acquire exclusive ownership. This operation will fail if there are threads with sharable or upgradable ownership, but it will maintain sharable ownership. Returns: If acquires exclusive ownership, returns true. Otherwise returns false. Throws: An exception derived from `interprocess_exception` on error.

20.     bool try_unlock_sharable_and_lock_upgradable();

### `named_upgradable_mutex` public static functions

1.     static bool remove(const char * name);

   Erases a named upgradable mutex from the system. Returns false on error. Never throws.