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      1 //
      2 // detail/scoped_lock.hpp
      3 // ~~~~~~~~~~~~~~~~~~~~~~
      4 //
      5 // Copyright (c) 2003-2015 Christopher M. Kohlhoff (chris at kohlhoff dot com)
      6 //
      7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
      8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
      9 //
     10 
     11 #ifndef ASIO_DETAIL_SCOPED_LOCK_HPP
     12 #define ASIO_DETAIL_SCOPED_LOCK_HPP
     13 
     14 
     15 #include "asio/detail/noncopyable.hpp"
     16 
     17 #include "asio/detail/push_options.hpp"
     18 
     19 namespace asio {
     20 namespace detail {
     21 
     22 // Helper class to lock and unlock a mutex automatically.
     23 template <typename Mutex>
     24 class scoped_lock
     25   : private noncopyable
     26 {
     27 public:
     28   // Tag type used to distinguish constructors.
     29   enum adopt_lock_t { adopt_lock };
     30 
     31   // Constructor adopts a lock that is already held.
     32   scoped_lock(Mutex& m, adopt_lock_t)
     33     : mutex_(m),
     34       locked_(true)
     35   {
     36   }
     37 
     38   // Constructor acquires the lock.
     39   explicit scoped_lock(Mutex& m)
     40     : mutex_(m)
     41   {
     42     mutex_.lock();
     43     locked_ = true;
     44   }
     45 
     46   // Destructor releases the lock.
     47   ~scoped_lock()
     48   {
     49     if (locked_)
     50       mutex_.unlock();
     51   }
     52 
     53   // Explicitly acquire the lock.
     54   void lock()
     55   {
     56     if (!locked_)
     57     {
     58       mutex_.lock();
     59       locked_ = true;
     60     }
     61   }
     62 
     63   // Explicitly release the lock.
     64   void unlock()
     65   {
     66     if (locked_)
     67     {
     68       mutex_.unlock();
     69       locked_ = false;
     70     }
     71   }
     72 
     73   // Test whether the lock is held.
     74   bool locked() const
     75   {
     76     return locked_;
     77   }
     78 
     79   // Get the underlying mutex.
     80   Mutex& mutex()
     81   {
     82     return mutex_;
     83   }
     84 
     85 private:
     86   // The underlying mutex.
     87   Mutex& mutex_;
     88 
     89   // Whether the mutex is currently locked or unlocked.
     90   bool locked_;
     91 };
     92 
     93 } // namespace detail
     94 } // namespace asio
     95 
     96 #include "asio/detail/pop_options.hpp"
     97 
     98 #endif // ASIO_DETAIL_SCOPED_LOCK_HPP
     99