. /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   23607 explicit conditionally_enabled_mutex(bool enabled = true) noexcept 33   20813 explicit conditionally_enabled_mutex(bool enabled = true) noexcept
HITCBC 34   23607 : enabled_(enabled) 34   20813 : enabled_(enabled)
35   { 35   {
HITCBC 36   23607 } 36   20813 }
37   37  
38   conditionally_enabled_mutex(conditionally_enabled_mutex const&) = delete; 38   conditionally_enabled_mutex(conditionally_enabled_mutex const&) = delete;
39   conditionally_enabled_mutex& operator=(conditionally_enabled_mutex const&) = delete; 39   conditionally_enabled_mutex& operator=(conditionally_enabled_mutex const&) = delete;
40   40  
41   bool enabled() const noexcept 41   bool enabled() const noexcept
42   { 42   {
43   return enabled_; 43   return enabled_;
44   } 44   }
45   45  
HITCBC 46   15487 void set_enabled(bool v) noexcept 46   13625 void set_enabled(bool v) noexcept
47   { 47   {
HITCBC 48   15487 enabled_ = v; 48   13625 enabled_ = v;
HITCBC 49   15487 } 49   13625 }
50   50  
51   // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex> 51   // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex>
HITCBC 52   93399 void lock() { if (enabled_) mutex_.lock(); } 52   81215 void lock() { if (enabled_) mutex_.lock(); }
HITCBC 53   93399 void unlock() { if (enabled_) mutex_.unlock(); } 53   81215 void unlock() { if (enabled_) mutex_.unlock(); }
54   bool try_lock() { return !enabled_ || mutex_.try_lock(); } 54   bool try_lock() { return !enabled_ || mutex_.try_lock(); }
55   55  
56   class scoped_lock 56   class scoped_lock
57   { 57   {
58   std::unique_lock<std::mutex> lock_; 58   std::unique_lock<std::mutex> lock_;
59   bool enabled_; 59   bool enabled_;
60   60  
61   public: 61   public:
HITCBC 62   848110 explicit scoped_lock(conditionally_enabled_mutex& m) 62   665478 explicit scoped_lock(conditionally_enabled_mutex& m)
HITCBC 63   848110 : lock_(m.mutex_, std::defer_lock) 63   665478 : lock_(m.mutex_, std::defer_lock)
HITCBC 64   848110 , enabled_(m.enabled_) 64   665478 , enabled_(m.enabled_)
65   { 65   {
HITCBC 66   848110 if (enabled_) 66   665478 if (enabled_)
HITCBC 67   848092 lock_.lock(); 67   665460 lock_.lock();
HITCBC 68   848110 } 68   665478 }
69   69  
70   scoped_lock(scoped_lock const&) = delete; 70   scoped_lock(scoped_lock const&) = delete;
71   scoped_lock& operator=(scoped_lock const&) = delete; 71   scoped_lock& operator=(scoped_lock const&) = delete;
72   72  
HITCBC 73   801561 void lock() 73   645487 void lock()
74   { 74   {
HITCBC 75   801561 if (enabled_) 75   645487 if (enabled_)
HITCBC 76   801553 lock_.lock(); 76   645479 lock_.lock();
HITCBC 77   801561 } 77   645487 }
78   78  
HITCBC 79   811128 void unlock() 79   655039 void unlock()
80   { 80   {
HITCBC 81   811128 if (enabled_) 81   655039 if (enabled_)
HITCBC 82   811120 lock_.unlock(); 82   655031 lock_.unlock();
HITCBC 83   811128 } 83   655039 }
84   84  
HITCBC 85   808513 bool owns_lock() const noexcept 85   651491 bool owns_lock() const noexcept
86   { 86   {
HITCBC 87   808513 return enabled_ && lock_.owns_lock(); 87   651491 return enabled_ && lock_.owns_lock();
88   } 88   }
89   89  
90   // Access the underlying unique_lock for condvar wait(). 90   // Access the underlying unique_lock for condvar wait().
91   // Only called when locking is enabled. 91   // Only called when locking is enabled.
HITCBC 92   10 std::unique_lock<std::mutex>& underlying() noexcept 92   8 std::unique_lock<std::mutex>& underlying() noexcept
93   { 93   {
HITCBC 94   10 return lock_; 94   8 return lock_;
95   } 95   }
96   }; 96   };
97   }; 97   };
98   98  
99   } // namespace boost::corosio::detail 99   } // namespace boost::corosio::detail
100   100  
101   #endif // BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP 101   #endif // BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP