From 0c29e86728713873868305af30497116f88e8635 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Wed, 12 Feb 2014 20:20:56 +0200
Subject: [PATCH] Add spinlock_std_atomic.hpp

---
 include/boost/smart_ptr/detail/spinlock.hpp   |  5 +-
 .../smart_ptr/detail/spinlock_std_atomic.hpp  | 83 +++++++++++++++++++
 2 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 include/boost/smart_ptr/detail/spinlock_std_atomic.hpp

diff --git a/include/boost/smart_ptr/detail/spinlock.hpp b/include/boost/smart_ptr/detail/spinlock.hpp
index 88d7ad6..deffb67 100644
--- a/include/boost/smart_ptr/detail/spinlock.hpp
+++ b/include/boost/smart_ptr/detail/spinlock.hpp
@@ -31,7 +31,10 @@
 #include <boost/config.hpp>
 #include <boost/smart_ptr/detail/sp_has_sync.hpp>
 
-#if defined( BOOST_SP_USE_PTHREADS )
+#if defined( BOOST_SP_USE_STD_ATOMIC )
+# include <boost/smart_ptr/detail/spinlock_std_atomic.hpp>
+
+#elif defined( BOOST_SP_USE_PTHREADS )
 #  include <boost/smart_ptr/detail/spinlock_pt.hpp>
 
 #elif defined(__GNUC__) && defined( __arm__ ) && !defined( __thumb__ )
diff --git a/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp b/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp
new file mode 100644
index 0000000..a61c1cd
--- /dev/null
+++ b/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp
@@ -0,0 +1,83 @@
+#ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
+#define BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//
+//  Copyright (c) 2014 Peter Dimov
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//  See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <boost/smart_ptr/detail/yield_k.hpp>
+#include <atomic>
+
+namespace boost
+{
+
+namespace detail
+{
+
+class spinlock
+{
+public:
+
+    std::atomic_flag v_;
+
+public:
+
+    bool try_lock()
+    {
+        return !v_.test_and_set( std::memory_order_acquire );
+    }
+
+    void lock()
+    {
+        for( unsigned k = 0; !try_lock(); ++k )
+        {
+            boost::detail::yield( k );
+        }
+    }
+
+    void unlock()
+    {
+        v_ .clear( std::memory_order_release );
+    }
+
+public:
+
+    class scoped_lock
+    {
+    private:
+
+        spinlock & sp_;
+
+        scoped_lock( scoped_lock const & );
+        scoped_lock & operator=( scoped_lock const & );
+
+    public:
+
+        explicit scoped_lock( spinlock & sp ): sp_( sp )
+        {
+            sp.lock();
+        }
+
+        ~scoped_lock()
+        {
+            sp_.unlock();
+        }
+    };
+};
+
+} // namespace detail
+} // namespace boost
+
+#define BOOST_DETAIL_SPINLOCK_INIT { ATOMIC_FLAG_INIT }
+
+#endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED