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//
 
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// Copyright (c) 2026 Michael Vandeberg
 
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//
 
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
 
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
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//
 
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// Official repository: https://github.com/cppalliance/corosio
 
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//
 
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#ifndef BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
 
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#define BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP
 
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#include <mutex>
 
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namespace boost::corosio::detail {
 
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/* Mutex wrapper that becomes a no-op when disabled.
 
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   When enabled (the default), lock/unlock delegate to an
 
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   underlying std::mutex. When disabled, all operations are
 
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   no-ops. The enabled flag is fixed after construction.
 
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   scoped_lock wraps std::unique_lock<std::mutex> internally
 
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   so that condvar wait paths (which require the real lock
 
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   type) compile and work in multi-threaded mode.
 
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*/
 
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class conditionally_enabled_mutex
 
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{
 
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    std::mutex mutex_;
 
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    bool enabled_;
 
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public:
 
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    explicit conditionally_enabled_mutex(bool enabled = true) noexcept
 
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        : enabled_(enabled)
 
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    {
 
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    }
 
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    conditionally_enabled_mutex(conditionally_enabled_mutex const&)            = delete;
 
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    conditionally_enabled_mutex& operator=(conditionally_enabled_mutex const&) = delete;
 
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    bool enabled() const noexcept
 
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    {
 
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        return enabled_;
 
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    }
 
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    void set_enabled(bool v) noexcept
 
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    {
 
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        enabled_ = v;
 
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    }
 
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    // Lockable interface — allows std::lock_guard<conditionally_enabled_mutex>
 
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    void lock() { if (enabled_) mutex_.lock(); }
 
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    void unlock() { if (enabled_) mutex_.unlock(); }
 
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    bool try_lock() { return !enabled_ || mutex_.try_lock(); }
 
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    class scoped_lock
 
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    {
 
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        std::unique_lock<std::mutex> lock_;
 
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        bool enabled_;
 
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    public:
 
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        explicit scoped_lock(conditionally_enabled_mutex& m)
 
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            : lock_(m.mutex_, std::defer_lock)
 
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            , enabled_(m.enabled_)
 
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        {
 
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            if (enabled_)
 
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                lock_.lock();
 
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        }
 
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        scoped_lock(scoped_lock const&)            = delete;
 
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        scoped_lock& operator=(scoped_lock const&) = delete;
 
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        void lock()
 
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        {
 
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            if (enabled_)
 
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                lock_.lock();
 
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        }
 
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        void unlock()
 
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        {
 
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            if (enabled_)
 
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                lock_.unlock();
 
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        }
 
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        bool owns_lock() const noexcept
 
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        {
 
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            return enabled_ && lock_.owns_lock();
 
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        }
 
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        // Access the underlying unique_lock for condvar wait().
 
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        // Only called when locking is enabled.
 
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        std::unique_lock<std::mutex>& underlying() noexcept
 
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        {
 
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            return lock_;
 
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        }
 
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    };
 
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};
 
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} // namespace boost::corosio::detail
 
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#endif // BOOST_COROSIO_DETAIL_CONDITIONALLY_ENABLED_MUTEX_HPP