. /include/boost/corosio /detail /conditionally_enabled_mutex.hpp
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1   // 1   //
2   // Copyright (c) 2026 Michael Vandeberg 2   // Copyright (c) 2026 Michael Vandeberg
3   // 3   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 4   // Distributed under the Boost Software License, Version 1.0. (See accompanying
5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   // 6   //
7   // Official repository: https://github.com/cppalliance/corosio 7   // Official repository: https://github.com/cppalliance/corosio
8   // 8   //
9   9  
10   #ifndef BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP 10   #ifndef BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
11   #define BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP 11   #define BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
12   12  
13   #include <mutex> 13   #include <mutex>
14   14  
15   namespace boost::corosio::detail { 15   namespace boost::corosio::detail {
16   16  
17   /* Mutex wrapper that becomes a no-op when disabled. 17   /* Mutex wrapper that becomes a no-op when disabled.
18   18  
19   When enabled (the default), lock/unlock delegate to an 19   When enabled (the default), lock/unlock delegate to an
20   underlying std::mutex. When disabled, all operations are 20   underlying std::mutex. When disabled, all operations are
21   no-ops. The enabled flag is fixed after construction. 21   no-ops. The enabled flag is fixed after construction.
22   22  
23   scoped_lock wraps std::unique_lock<std::mutex> internally 23   scoped_lock wraps std::unique_lock<std::mutex> internally
24   so that condvar wait paths (which require the real lock 24   so that condvar wait paths (which require the real lock
25   type) compile and work in multi-threaded mode. 25   type) compile and work in multi-threaded mode.
26   */ 26   */
27   class conditionally_enabled_mutex 27   class conditionally_enabled_mutex
28   { 28   {
29   std::mutex mutex_; 29   std::mutex mutex_;
30   bool enabled_; 30   bool enabled_;
31   31  
32   public: 32   public:
HITCBC 33   16837 explicit conditionally_enabled_mutex(bool enabled = true) noexcept 33   16814 explicit conditionally_enabled_mutex(bool enabled = true) noexcept
HITCBC 34   16837 : enabled_(enabled) 34   16814 : enabled_(enabled)
35   { 35   {
HITCBC 36   16837 } 36   16814 }
37   37  
38   conditionally_enabled_mutex(conditionally_enabled_mutex const&) = delete; 38   conditionally_enabled_mutex(conditionally_enabled_mutex const&) = delete;
39   conditionally_enabled_mutex& 39   conditionally_enabled_mutex&
40   operator=(conditionally_enabled_mutex const&) = delete; 40   operator=(conditionally_enabled_mutex const&) = delete;
41   41  
HITCBC 42   23211 bool enabled() const noexcept 42   23602 bool enabled() const noexcept
43   { 43   {
HITCBC 44   23211 return enabled_; 44   23602 return enabled_;
45   } 45   }
46   46  
HITCBC 47   4510 void set_enabled(bool v) noexcept 47   4516 void set_enabled(bool v) noexcept
48   { 48   {
HITCBC 49   4510 enabled_ = v; 49   4516 enabled_ = v;
HITCBC 50   4510 } 50   4516 }
51   51  
52   // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex> 52   // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex>
HITCBC 53   227760 void lock() 53   232113 void lock()
54   { 54   {
HITCBC 55   227760 if (enabled_) 55   232113 if (enabled_)
HITCBC 56   227718 mutex_.lock(); 56   232071 mutex_.lock();
HITCBC 57   227760 } 57   232113 }
HITCBC 58   227760 void unlock() 58   232113 void unlock()
59   { 59   {
HITCBC 60   227760 if (enabled_) 60   232113 if (enabled_)
HITCBC 61   227718 mutex_.unlock(); 61   232071 mutex_.unlock();
HITCBC 62   227760 } 62   232113 }
63   bool try_lock() 63   bool try_lock()
64   { 64   {
65   return !enabled_ || mutex_.try_lock(); 65   return !enabled_ || mutex_.try_lock();
66   } 66   }
67   67  
68   class scoped_lock 68   class scoped_lock
69   { 69   {
70   std::unique_lock<std::mutex> lock_; 70   std::unique_lock<std::mutex> lock_;
71   bool enabled_; 71   bool enabled_;
72   72  
73   public: 73   public:
HITCBC 74   458936 explicit scoped_lock(conditionally_enabled_mutex& m) 74   444196 explicit scoped_lock(conditionally_enabled_mutex& m)
HITCBC 75   458936 : lock_(m.mutex_, std::defer_lock) 75   444196 : lock_(m.mutex_, std::defer_lock)
HITCBC 76   458936 , enabled_(m.enabled_) 76   444196 , enabled_(m.enabled_)
77   { 77   {
HITCBC 78   458936 if (enabled_) 78   444196 if (enabled_)
HITCBC 79   458877 lock_.lock(); 79   444135 lock_.lock();
HITCBC 80   458936 } 80   444196 }
81   81  
82   scoped_lock(scoped_lock const&) = delete; 82   scoped_lock(scoped_lock const&) = delete;
83   scoped_lock& operator=(scoped_lock const&) = delete; 83   scoped_lock& operator=(scoped_lock const&) = delete;
84   84  
HITCBC 85   820926 void lock() 85   791179 void lock()
86   { 86   {
HITCBC 87   820926 if (enabled_) 87   791179 if (enabled_)
HITCBC 88   820917 lock_.lock(); 88   791170 lock_.lock();
HITCBC 89   820926 } 89   791179 }
90   90  
HITCBC 91   862513 void unlock() 91   832624 void unlock()
92   { 92   {
HITCBC 93   862513 if (enabled_) 93   832624 if (enabled_)
HITCBC 94   862505 lock_.unlock(); 94   832616 lock_.unlock();
HITCBC 95   862513 } 95   832624 }
96   96  
HITCBC 97   832031 bool owns_lock() const noexcept 97   799884 bool owns_lock() const noexcept
98   { 98   {
HITCBC 99   832031 return enabled_ && lock_.owns_lock(); 99   799884 return enabled_ && lock_.owns_lock();
100   } 100   }
101   101  
102   // Access the underlying unique_lock for condvar wait(). 102   // Access the underlying unique_lock for condvar wait().
103   // Only called when locking is enabled. 103   // Only called when locking is enabled.
HITCBC 104   780 std::unique_lock<std::mutex>& underlying() noexcept 104   857 std::unique_lock<std::mutex>& underlying() noexcept
105   { 105   {
HITCBC 106   780 return lock_; 106   857 return lock_;
107   } 107   }
108   }; 108   };
109   }; 109   };
110   110  
111   } // namespace boost::corosio::detail 111   } // namespace boost::corosio::detail
112   112  
113   #endif // BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP 113   #endif // BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP