. /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   20698 explicit conditionally_enabled_mutex(bool enabled = true) noexcept 33   20919 explicit conditionally_enabled_mutex(bool enabled = true) noexcept
HITCBC 34   20698 : enabled_(enabled) 34   20919 : enabled_(enabled)
35   { 35   {
HITCBC 36   20698 } 36   20919 }
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  
42   bool enabled() const noexcept 42   bool enabled() const noexcept
43   { 43   {
44   return enabled_; 44   return enabled_;
45   } 45   }
46   46  
HITCBC 47   13328 void set_enabled(bool v) noexcept 47   13475 void set_enabled(bool v) noexcept
48   { 48   {
HITCBC 49   13328 enabled_ = v; 49   13475 enabled_ = v;
HITCBC 50   13328 } 50   13475 }
51   51  
52   // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex> 52   // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex>
HITCBC 53   72219 void lock() 53   73169 void lock()
54   { 54   {
HITCBC 55   72219 if (enabled_) 55   73169 if (enabled_)
HITCBC 56   72219 mutex_.lock(); 56   73169 mutex_.lock();
HITCBC 57   72219 } 57   73169 }
HITCBC 58   72219 void unlock() 58   73169 void unlock()
59   { 59   {
HITCBC 60   72219 if (enabled_) 60   73169 if (enabled_)
HITCBC 61   72219 mutex_.unlock(); 61   73169 mutex_.unlock();
HITCBC 62   72219 } 62   73169 }
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   855712 explicit scoped_lock(conditionally_enabled_mutex& m) 74   858019 explicit scoped_lock(conditionally_enabled_mutex& m)
HITCBC 75   855712 : lock_(m.mutex_, std::defer_lock) 75   858019 : lock_(m.mutex_, std::defer_lock)
HITCBC 76   855712 , enabled_(m.enabled_) 76   858019 , enabled_(m.enabled_)
77   { 77   {
HITCBC 78   855712 if (enabled_) 78   858019 if (enabled_)
HITCBC 79   855692 lock_.lock(); 79   857999 lock_.lock();
HITCBC 80   855712 } 80   858019 }
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   782544 void lock() 85   784647 void lock()
86   { 86   {
HITCBC 87   782544 if (enabled_) 87   784647 if (enabled_)
HITCBC 88   782536 lock_.lock(); 88   784639 lock_.lock();
HITCBC 89   782544 } 89   784647 }
90   90  
HITCBC 91   799294 void unlock() 91   801470 void unlock()
92   { 92   {
HITCBC 93   799294 if (enabled_) 93   801470 if (enabled_)
HITCBC 94   799286 lock_.unlock(); 94   801462 lock_.unlock();
HITCBC 95   799294 } 95   801470 }
96   96  
HITCBC 97   791611 bool owns_lock() const noexcept 97   794093 bool owns_lock() const noexcept
98   { 98   {
HITCBC 99   791611 return enabled_ && lock_.owns_lock(); 99   794093 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   25 std::unique_lock<std::mutex>& underlying() noexcept 104   19 std::unique_lock<std::mutex>& underlying() noexcept
105   { 105   {
HITCBC 106   25 return lock_; 106   19 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