From 9ac9bb98f307156c02fa19ea747cf5eb1d2dcadf Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 4 Aug 2011 13:29:42 +0200
Subject: Add support for value wrappers

Wrapper is a class that wraps another type. Examples of wrappers are
various smart pointers, holders, etc. A wrapper can be transparent or
it can handle the NULL semantics.

The new odb::nullable class template is a NULL wrapper that helps
to add the NULL semantics to a value type.

New test: common/wrapper.
---
 odb/tr1/wrapper-traits.hxx | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 odb/tr1/wrapper-traits.hxx

(limited to 'odb/tr1')

diff --git a/odb/tr1/wrapper-traits.hxx b/odb/tr1/wrapper-traits.hxx
new file mode 100644
index 0000000..e65e2d7
--- /dev/null
+++ b/odb/tr1/wrapper-traits.hxx
@@ -0,0 +1,63 @@
+// file      : odb/tr1/wrapper-traits.hxx
+// author    : Boris Kolpackov <boris@codesynthesis.com>
+// copyright : Copyright (c) 2009-2011 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#ifndef ODB_TR1_WRAPPER_TRAITS_HXX
+#define ODB_TR1_WRAPPER_TRAITS_HXX
+
+#include <odb/pre.hxx>
+
+//
+// This header assumes that the necessary TR1 header has already
+// been included.
+//
+
+#include <odb/wrapper-traits.hxx>
+
+namespace odb
+{
+  // Specialization for std::tr1::shared_ptr.
+  //
+  template <typename T>
+  class wrapper_traits< std::tr1::shared_ptr<T> >
+  {
+  public:
+    typedef T wrapped_type;
+    typedef std::tr1::shared_ptr<T> wrapper_type;
+
+    static const bool null_handler = true;
+    static const bool null_default = false;
+
+    static bool
+    get_null (const wrapper_type& p)
+    {
+      return !p;
+    }
+
+    static void
+    set_null (wrapper_type& p)
+    {
+      p.reset ();
+    }
+
+    static const wrapped_type&
+    get_ref (const wrapper_type& p)
+    {
+      return *p;
+    }
+
+    static wrapped_type&
+    set_ref (wrapper_type& p)
+    {
+      if (!p)
+        p.reset (new wrapped_type);
+
+      return *p;
+    }
+  };
+}
+
+#include <odb/post.hxx>
+
+#endif // ODB_TR1_WRAPPER_TRAITS_HXX
-- 
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