epoc32/include/stdapis/boost/detail/atomic_count.hpp
branchSymbian2
changeset 2 2fe1408b6811
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/epoc32/include/stdapis/boost/detail/atomic_count.hpp	Tue Mar 16 16:12:26 2010 +0000
@@ -0,0 +1,108 @@
+#ifndef BOOST_DETAIL_ATOMIC_COUNT_HPP_INCLUDED
+#define BOOST_DETAIL_ATOMIC_COUNT_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//
+//  boost/detail/atomic_count.hpp - thread/SMP safe reference counter
+//
+//  Copyright (c) 2001, 2002 Peter Dimov and Multi Media Ltd.
+//
+// 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)
+//
+//  typedef <implementation-defined> boost::detail::atomic_count;
+//
+//  atomic_count a(n);
+//
+//    (n is convertible to long)
+//
+//    Effects: Constructs an atomic_count with an initial value of n
+//
+//  a;
+//
+//    Returns: (long) the current value of a
+//
+//  ++a;
+//
+//    Effects: Atomically increments the value of a
+//    Returns: nothing
+//
+//  --a;
+//
+//    Effects: Atomically decrements the value of a
+//    Returns: (long) zero if the new value of a is zero,
+//      unspecified non-zero value otherwise (usually the new value)
+//
+//    Important note: when --a returns zero, it must act as a
+//      read memory barrier (RMB); i.e. the calling thread must
+//      have a synchronized view of the memory
+//
+//    On Intel IA-32 (x86) memory is always synchronized, so this
+//      is not a problem.
+//
+//    On many architectures the atomic instructions already act as
+//      a memory barrier.
+//
+//    This property is necessary for proper reference counting, since
+//      a thread can update the contents of a shared object, then
+//      release its reference, and another thread may immediately
+//      release the last reference causing object destruction.
+//
+//    The destructor needs to have a synchronized view of the
+//      object to perform proper cleanup.
+//
+//    Original example by Alexander Terekhov:
+//
+//    Given:
+//
+//    - a mutable shared object OBJ;
+//    - two threads THREAD1 and THREAD2 each holding 
+//      a private smart_ptr object pointing to that OBJ.
+//
+//    t1: THREAD1 updates OBJ (thread-safe via some synchronization)
+//      and a few cycles later (after "unlock") destroys smart_ptr;
+//
+//    t2: THREAD2 destroys smart_ptr WITHOUT doing any synchronization 
+//      with respect to shared mutable object OBJ; OBJ destructors
+//      are called driven by smart_ptr interface...
+//
+
+#include <boost/config.hpp>
+
+#ifndef BOOST_HAS_THREADS
+
+namespace boost
+{
+
+namespace detail
+{
+
+typedef long atomic_count;
+
+}
+
+}
+
+#elif defined(BOOST_AC_USE_PTHREADS)
+#  include <boost/detail/atomic_count_pthreads.hpp>
+#elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
+#  include <boost/detail/atomic_count_win32.hpp>
+#elif defined(__GLIBCPP__) || defined(__GLIBCXX__)
+#  include <boost/detail/atomic_count_gcc.hpp>
+#elif defined(BOOST_HAS_PTHREADS)
+#  define BOOST_AC_USE_PTHREADS
+#  include <boost/detail/atomic_count_pthreads.hpp>
+#else
+
+// Use #define BOOST_DISABLE_THREADS to avoid the error
+#error Unrecognized threading platform
+
+#endif
+
+#endif // #ifndef BOOST_DETAIL_ATOMIC_COUNT_HPP_INCLUDED