diff options
Diffstat (limited to 'third_party/immer/immer/refcount/refcount_policy.hpp')
-rw-r--r-- | third_party/immer/immer/refcount/refcount_policy.hpp | 101 |
1 files changed, 0 insertions, 101 deletions
diff --git a/third_party/immer/immer/refcount/refcount_policy.hpp b/third_party/immer/immer/refcount/refcount_policy.hpp deleted file mode 100644 index a7a282cd13a7..000000000000 --- a/third_party/immer/immer/refcount/refcount_policy.hpp +++ /dev/null @@ -1,101 +0,0 @@ -// -// immer: immutable data structures for C++ -// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente -// -// This software is distributed under the Boost Software License, Version 1.0. -// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt -// - -#pragma once - -#include <immer/refcount/no_refcount_policy.hpp> - -#include <atomic> -#include <cassert> -#include <thread> -#include <utility> - -// This has been shamelessly copied from boost... -#if defined(_MSC_VER) && _MSC_VER >= 1310 && \ - (defined(_M_IX86) || defined(_M_X64)) && !defined(__c2__) -extern "C" void _mm_pause(); -#define IMMER_SMT_PAUSE _mm_pause() -#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) -#define IMMER_SMT_PAUSE __asm__ __volatile__("rep; nop" : : : "memory") -#endif - -namespace immer { - -// This is an atomic spinlock similar to the one used by boost to provide -// "atomic" shared_ptr operations. It also does not differ much from the one -// from libc++ or libstdc++... -struct spinlock -{ - std::atomic_flag v_{}; - - bool try_lock() { return !v_.test_and_set(std::memory_order_acquire); } - - void lock() - { - for (auto k = 0u; !try_lock(); ++k) { - if (k < 4) - continue; -#ifdef IMMER_SMT_PAUSE - else if (k < 16) - IMMER_SMT_PAUSE; -#endif - else - std::this_thread::yield(); - } - } - - void unlock() { v_.clear(std::memory_order_release); } - - struct scoped_lock - { - scoped_lock(const scoped_lock&) = delete; - scoped_lock& operator=(const scoped_lock&) = delete; - - explicit scoped_lock(spinlock& sp) - : sp_{sp} - { - sp.lock(); - } - - ~scoped_lock() { sp_.unlock(); } - - private: - spinlock& sp_; - }; -}; - -/*! - * A reference counting policy implemented using an *atomic* `int` - * count. It is **thread-safe**. - */ -struct refcount_policy -{ - using spinlock_type = spinlock; - - mutable std::atomic<int> refcount; - - refcount_policy() - : refcount{1} {}; - refcount_policy(disowned) - : refcount{0} - {} - - void inc() { refcount.fetch_add(1, std::memory_order_relaxed); } - - bool dec() { return 1 == refcount.fetch_sub(1, std::memory_order_acq_rel); } - - void dec_unsafe() - { - assert(refcount.load() > 1); - refcount.fetch_sub(1, std::memory_order_relaxed); - } - - bool unique() { return refcount == 1; } -}; - -} // namespace immer |