Andrew Zambazos
54 lines
1.9 KiB
C++
54 lines
1.9 KiB
C++
/**************************************************************************************************
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* This file is a part of Ultralight. *
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* *
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* See <https://ultralig.ht> for licensing and more. *
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* *
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* (C) 2024 Ultralight, Inc. *
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**************************************************************************************************/
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#pragma once
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#include <Ultralight/Defines.h>
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#include <atomic>
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#include <mutex> // for std::lock_guard<>
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namespace ultralight {
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///
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/// Tiny, efficient spinlock that is optimized for short locking periods but will still
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/// intelligently yield the current thread and save CPU if the lock is held longer.
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///
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/// Can be used in place of std::mutex since it implements the STL's Lockable interface.
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///
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class Lock {
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public:
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constexpr Lock() = default;
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UL_ALWAYS_INLINE void lock() noexcept {
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// Optimistically assume the lock is free on the first try
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if (!lock_.exchange(true, std::memory_order_acquire))
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return;
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contended_lock();
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}
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UL_ALWAYS_INLINE bool try_lock() noexcept {
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// First do a relaxed load to check if lock is free in order to prevent
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// unnecessary cache misses if someone does while(!try_lock())
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return !lock_.load(std::memory_order_relaxed)
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&& !lock_.exchange(true, std::memory_order_acquire);
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}
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UL_ALWAYS_INLINE void unlock() noexcept { lock_.store(false, std::memory_order_release); }
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protected:
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Lock(const Lock&) = delete;
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Lock& operator=(const Lock&) = delete;
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void contended_lock() noexcept;
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std::atomic<bool> lock_ = { 0 };
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};
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using LockHolder = std::lock_guard<Lock>;
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} // namespace ultralight
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