boost::detail::spinlock added.

[SVN r43950]

include/boost/detail/spinlock_sync.hpp

@@ -0,0 +1,83 @@
+#ifndef BOOST_DETAIL_SPINLOCK_SYNC_HPP_INCLUDED
+#define BOOST_DETAIL_SPINLOCK_SYNC_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//
+//  Copyright (c) 2008 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/detail/yield_k.hpp>
+
+namespace boost
+{
+
+namespace detail
+{
+
+class spinlock
+{
+public:
+
+    int v_;
+
+public:
+
+    bool try_lock()
+    {
+        int r = __sync_lock_test_and_set( &v_, 1 );
+        return r == 0;
+    }
+
+    void lock()
+    {
+        for( unsigned k = 0; !try_lock(); ++k )
+        {
+            boost::detail::yield( k );
+        }
+    }
+
+    void unlock()
+    {
+        __sync_lock_release( &v_ );
+    }
+
+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 {0}
+
+#endif // #ifndef BOOST_DETAIL_SPINLOCK_SYNC_HPP_INCLUDED