Added an implementation of sp_counted_base for g++/x86

[SVN r27933]

include/boost/detail/sp_counted_base_gcc_x86.hpp

@@ -0,0 +1,158 @@
+#ifndef BOOST_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
+#define BOOST_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//
+//  detail/sp_counted_base_gcc_x86.hpp - g++ on 486+ or AMD64
+//
+//  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
+//  Copyright 2004-2005 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)
+//
+//
+//  Lock-free algorithm by Alexander Terekhov
+//
+//  Thanks to Ben Hitchings for the #weak + (#shared != 0)
+//  formulation
+//
+
+#include <typeinfo>
+
+namespace boost
+{
+
+namespace detail
+{
+
+inline long atomic_exchange_and_add( long * pw, long dv )
+{
+    // long r = *pw;
+    // *pw += dv;
+    // return r;
+
+    long r;
+
+    __asm__ __volatile__
+    (
+        "lock\n\t"
+        "xadd %1, %0":
+        "=m"( *pw ), "=r"( r ): // outputs (%0, %1)
+        "0"( *pw ), "1"( dv ): // inputs (%0, %1)
+        "memory", "cc" // clobbers
+    );
+
+    return r;
+}
+
+inline long atomic_conditional_increment( long * pw )
+{
+    // long r = *pw;
+    // if( r != 0 ) ++*pw;
+    // return r;
+
+    long r;
+
+    __asm__ __volatile__
+    (
+        "movl %0, %%eax\n\t"
+        "0:\n\t"
+        "test %%eax, %%eax\n\t"
+        "je 1f\n\t"
+        "leal 1(%%eax), %%ebx\n\t"
+        "lock\n\t"
+        "cmpxchgl %%ebx, %0\n\t"
+        "jne 0b\n\t"
+        "1:":
+        "=m"( *pw ), "=eax"( r ): // outputs (%0, %1)
+        "0"( *pw ): // input (%0)
+        "ebx", "memory", "cc" // clobbers
+    );
+
+    return r;
+}
+
+class sp_counted_base
+{
+private:
+
+    sp_counted_base( sp_counted_base const & );
+    sp_counted_base & operator= ( sp_counted_base const & );
+
+    long use_count_;        // #shared
+    long weak_count_;       // #weak + (#shared != 0)
+
+public:
+
+    sp_counted_base(): use_count_( 1 ), weak_count_( 1 )
+    {
+    }
+
+    virtual ~sp_counted_base() // nothrow
+    {
+    }
+
+    // dispose() is called when use_count_ drops to zero, to release
+    // the resources managed by *this.
+
+    virtual void dispose() = 0; // nothrow
+
+    // destroy() is called when weak_count_ drops to zero.
+
+    virtual void destroy() // nothrow
+    {
+        delete this;
+    }
+
+    virtual void * get_deleter( std::type_info const & ti ) = 0;
+
+    void add_ref_copy()
+    {
+        atomic_exchange_and_add( &use_count_, +1 );
+    }
+
+    bool add_ref_lock() // true on success
+    {
+		return atomic_conditional_increment( &use_count_ ) != 0;
+    }
+
+    void release() // nothrow
+    {
+        if( atomic_exchange_and_add( &use_count_, -1 ) == 1 )
+        {
+            dispose();
+            weak_release();
+        }
+    }
+
+    void weak_add_ref() // nothrow
+    {
+        atomic_exchange_and_add( &weak_count_, +1 );
+    }
+
+    void weak_release() // nothrow
+    {
+        if( atomic_exchange_and_add( &weak_count_, -1 ) == 1 )
+        {
+            destroy();
+        }
+    }
+
+    long use_count() const // nothrow
+    {
+        return static_cast<long const volatile &>( use_count_ );
+    }
+};
+
+} // namespace detail
+
+} // namespace boost
+
+#endif  // #ifndef BOOST_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED