Ticket #2056: single_patch_of_boost_array_swap_modifications.patch

boost/utility/swap.hpp

@@ -1 @@
-// Copyright (C) 2007 Steven Watanabe, Joseph Gauterin
+// Copyright (C) 2007, 2008 Steven Watanabe, Joseph Gauterin
 //
 // 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)
 // For more information, see http://www.boost.org
+//
+// Update:
+// 29 June 2008 (Added support for built-in arrays.) Niels Dekker  
 
 
 #ifndef BOOST_UTILITY_SWAP_HPP
 #define BOOST_UTILITY_SWAP_HPP
 
 #include <algorithm> //for std::swap
+#include <cstddef> //for std::size_t
 
 namespace boost_swap_impl
 {
@@ -19 +23 @@
     using std::swap;//use std::swap if argument dependent lookup fails
     swap(left,right);
   }
+
+  template<class T, std::size_t N>
+  void swap_impl(T (& left)[N], T (& right)[N])
+  {
+    for (std::size_t i = 0; i < N; ++i)
+    {
+      ::boost_swap_impl::swap_impl(left[i], right[i]);
+    }
+  }
 }
 
 namespace boost

libs/utility/swap.html

@@ -26 +26 @@
     <p>
       The alternative to using argument dependent lookup in this situation is to provide a template specialization of std::swap for every type that requires a specialized swap. Although this is legal C++, no boost libraries use this method, whereas many boost libraries provide specialized swap functions in their own namespaces.
     </p>
+    <p>
+      <tt>boost::swap</tt> also supports swapping built-in arrays. Note that <tt>std::swap</tt> doesn't yet do so, but a request to add an overload of <tt>std::swap</tt> for built-in arrays has been well received by the Library Working Group of the C++ Standards Committee: <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#809">LWG issue 809. std::swap should be overloaded for array types</a>
+      <tt>boost::swap</tt> is no-throw for arrays whose element type has a no-throw swap. However, if the swap function of the element type provides the strong guarantee, then <tt>boost::swap</tt> only provides the basic guarantee, for arrays of size > 1.
+    </p>
     
     <!-- Requirements -->
     <h2>Requirements</h2>
@@ -42 +46 @@
     <ul>
       <li>A template specialization of std::swap exists for T</li>
     </ul>
+    <p>Or:</p>
+    <ul>
+      <li>T is a built-in array of swappable elements</li>
+    </ul>
 
     
     <!-- Portability -->
@@ -56 +64 @@
       <li>
         <em>Steven Wanatabe</em> - for the idea to use a barrier namespaces, enabling the function to have the name '<tt>swap</tt>' without introducing ambiguity or infinite recursion.
       </li>
+      <li>
+        <em>Niels Dekker</em> - for adding support for built-in arrays
+      </li>
       <li>        
         <em><a href="mailto:Joseph.Gauterin@googlemail.com">Joseph Gauterin</a></em> - for the initial idea, final implementation, tests, and documentation.
       </li>
@@ -63 +74 @@
 
     <!-- Copyright info -->    
     <hr/>
-    <p>Revised: 3rd October 2007</p>
+    <p>Revised: 29 June 2008</p>
     <p>
       Copyright 2007 Joseph Gauterin. Use, modification, and distribution are subject to the Boost Software License, Version 1.0.
       (See accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or a copy at &lt;<a href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>&gt;.)

libs/utility/swap/test/Jamfile.v2

@@ -1 @@
-# Copyright (c) 2007 Joseph Gauterin
+# Copyright (c) 2007, 2008 Joseph Gauterin
 #
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at
@@ -20 +20 @@
     [ run specialized_in_global.cpp ../../../test/build//boost_test_exec_monitor/<link>static ]
     [ run specialized_in_other.cpp ../../../test/build//boost_test_exec_monitor/<link>static  ]
     [ run specialized_in_std.cpp ../../../test/build//boost_test_exec_monitor/<link>static    ]
+    [ run swap_arrays.cpp ../../../test/build//boost_test_exec_monitor/<link>static    ]
     ;
     
 

libs/utility/swap/test/swap_arrays.cpp

@@ +1 @@
+// Copyright (c) 2008 Joseph Gauterin, Niels Dekker
+//
+// 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/utility/swap.hpp>
+#define BOOST_INCLUDE_MAIN
+#include <boost/test/test_tools.hpp>
+
+//Put test class in the global namespace
+#include "./swap_test_class.hpp"
+
+
+int test_main(int, char*[])
+{
+  const std::size_t dimension = 7;
+
+  swap_test_class array1[dimension];
+  swap_test_class array2[dimension];
+  boost::swap(array1, array2);
+
+  BOOST_CHECK_EQUAL(swap_test_class::swap_count(), dimension);
+  BOOST_CHECK_EQUAL(swap_test_class::copy_count(), 0);
+
+  swap_test_class::reset();
+
+  const std::size_t firstDimension = 3;
+  const std::size_t secondDimension = 4;
+
+  swap_test_class two_d_array1[firstDimension][secondDimension];
+  swap_test_class two_d_array2[firstDimension][secondDimension];
+  boost::swap(two_d_array1, two_d_array1);
+
+  BOOST_CHECK_EQUAL(swap_test_class::swap_count(), firstDimension*secondDimension);
+  BOOST_CHECK_EQUAL(swap_test_class::copy_count(), 0);
+
+  return 0;
+}