78 lines
2.2 KiB
C++
78 lines
2.2 KiB
C++
/**
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Copyright (c) 2013 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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C++11 does not support std::shared_mutex and std::shared_lock yet.
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This piece of code is based on the proposal submitted to the C++
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standardization committee. The proposal was written by Howard
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Hinnant. The proposal is also part of the Boost library which is
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licensed under http://www.boost.org/LICENSE_1_0.txt
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*/
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#pragma once
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#include <climits>
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#include "util/thread.h"
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namespace lean {
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#if defined(LEAN_MULTI_THREAD)
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class shared_mutex {
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mutex m_mutex;
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thread::id m_rw_owner;
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unsigned m_rw_counter;
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condition_variable m_gate1;
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condition_variable m_gate2;
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unsigned m_state;
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static constexpr unsigned write_entered = 1u << (sizeof(unsigned)*8 - 1);
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static constexpr unsigned readers = ~write_entered;
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public:
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shared_mutex();
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~shared_mutex();
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shared_mutex(shared_mutex const &) = delete;
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shared_mutex(shared_mutex &&) = delete;
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shared_mutex& operator=(shared_mutex const &) = delete;
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shared_mutex&& operator=(shared_mutex &&) = delete;
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void lock();
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bool try_lock();
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void unlock();
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void lock_shared();
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bool try_lock_shared();
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void unlock_shared();
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};
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#else
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class shared_mutex {
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public:
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shared_mutex() {}
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shared_mutex(shared_mutex const &) = delete;
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shared_mutex(shared_mutex &&) = delete;
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shared_mutex& operator=(shared_mutex const &) = delete;
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shared_mutex&& operator=(shared_mutex &&) = delete;
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void lock() {}
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bool try_lock() { return true; }
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void unlock() {}
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void lock_shared() {}
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bool try_lock_shared() { return true; }
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void unlock_shared() {}
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};
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#endif
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class shared_lock {
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shared_mutex & m_mutex;
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public:
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shared_lock(shared_mutex & m):m_mutex(m) { m_mutex.lock_shared(); }
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~shared_lock() { m_mutex.unlock_shared(); }
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};
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class exclusive_lock {
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shared_mutex & m_mutex;
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public:
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exclusive_lock(shared_mutex & m):m_mutex(m) { m_mutex.lock(); }
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~exclusive_lock() { m_mutex.unlock(); }
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};
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}
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