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authorBoris Kolpackov <boris@codesynthesis.com>2011-08-04 13:29:42 +0200
committerBoris Kolpackov <boris@codesynthesis.com>2011-08-04 13:29:42 +0200
commit9ac9bb98f307156c02fa19ea747cf5eb1d2dcadf (patch)
tree8237f586c0198b82c186e7e7700ff9aaf7405bd5 /odb/tr1
parent1d2e161846310145c8bf4343a041818c57ca611e (diff)
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.
Diffstat (limited to 'odb/tr1')
-rw-r--r--odb/tr1/wrapper-traits.hxx63
1 files changed, 63 insertions, 0 deletions
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