整理

include/boost/smart_ptr/detail/yield_k.hpp

@@ -0,0 +1,49 @@
+#ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED
+#define BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+// boost/smart_ptr/detail/yield_k.hpp
+//
+// Copyright 2008, 2020 Peter Dimov
+//
+// inline void boost::detail::yield( unsigned k );
+//
+//   Typical use:
+//   for( unsigned k = 0; !try_lock(); ++k ) yield( k );
+//
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/core/yield_primitives.hpp>
+
+namespace boost
+{
+
+namespace detail
+{
+
+inline void yield( unsigned k )
+{
+    // Experiments on Windows and Fedora 32 show that a single pause,
+    // followed by an immediate sp_thread_sleep(), is best.
+
+    if( k & 1 )
+    {
+        boost::core::sp_thread_sleep();
+    }
+    else
+    {
+        boost::core::sp_thread_pause();
+    }
+}
+
+} // namespace detail
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SMART_PTR_DETAIL_YIELD_K_HPP_INCLUDED