From b366c3176462d470e445bc8aeb93a13df87e0518 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 7 Jan 2013 12:51:22 +0200
Subject: Cleanup object cache position type

---
 odb/cache-traits.hxx | 22 ++++++++++++++++------
 odb/session.hxx      | 18 +++++++++++-------
 odb/session.ixx      |  2 +-
 odb/session.txx      |  4 ++--
 4 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/odb/cache-traits.hxx b/odb/cache-traits.hxx
index c0c1272..6a6741e 100644
--- a/odb/cache-traits.hxx
+++ b/odb/cache-traits.hxx
@@ -27,7 +27,17 @@ namespace odb
     typedef odb::pointer_traits<pointer_type> pointer_traits;
     typedef typename pointer_traits::element_type object_type;
     typedef typename object_traits<object_type>::id_type id_type;
-    typedef session::object_position<object_type> position_type;
+
+    struct position_type
+    {
+      typedef session::position<object_type> base_type;
+
+      position_type (): empty_ (true) {}
+      position_type (const base_type& pos): empty_ (false), pos_ (pos) {}
+
+      bool empty_;
+      base_type pos_;
+    };
 
     struct insert_guard
     {
@@ -35,13 +45,13 @@ namespace odb
       insert_guard (const position_type& pos): pos_ (pos) {}
       ~insert_guard () {erase (pos_);}
 
-      position_type
+      const position_type&
       position () const {return pos_;}
 
       void
-      release () {pos_.map_ = 0;}
+      release () {pos_.empty_ = true;}
 
-      // Note: doesn't call erase() on the old position (assumes not set).
+      // Note: doesn't call erase() on the old position (assumes empty).
       //
       void
       reset (const position_type& pos) {pos_ = pos;}
@@ -94,8 +104,8 @@ namespace odb
     static void
     erase (const position_type& p)
     {
-      if (p.map_ != 0)
-        session::current ().erase<object_type> (p);
+      if (!p.empty_)
+        session::current ().erase<object_type> (p.pos_);
     }
   };
 
diff --git a/odb/session.hxx b/odb/session.hxx
index cfeebce..f9c8739 100644
--- a/odb/session.hxx
+++ b/odb/session.hxx
@@ -83,22 +83,26 @@ namespace odb
     // Object cache.
     //
   public:
+    // Position in the cache of an inserted element. The requirements
+    // for this class template are: default and copy-constructible and
+    // copy-assignable. In particular, a standard iterator can be used
+    // as a position.
+    //
     template <typename T>
-    struct object_position
+    struct position
     {
-      typedef T object_type;
-      typedef object_map<object_type> map;
+      typedef object_map<T> map;
       typedef typename map::iterator iterator;
 
-      object_position (): map_ (0) {}
-      object_position (map& m, const iterator& p): map_ (&m), pos_ (p) {}
+      position () {}
+      position (map& m, const iterator& p): map_ (&m), pos_ (p) {}
 
       map* map_;
       iterator pos_;
     };
 
     template <typename T>
-    object_position<T>
+    position<T>
     insert (database_type&,
             const typename object_traits<T>::id_type&,
             const typename object_traits<T>::pointer_type&);
@@ -113,7 +117,7 @@ namespace odb
 
     template <typename T>
     void
-    erase (const object_position<T>&);
+    erase (const position<T>&);
 
   protected:
     typedef std::map<const std::type_info*,
diff --git a/odb/session.ixx b/odb/session.ixx
index b359e95..50a2ca1 100644
--- a/odb/session.ixx
+++ b/odb/session.ixx
@@ -8,7 +8,7 @@ namespace odb
 {
   template <typename T>
   inline void session::
-  erase (const object_position<T>& p)
+  erase (const position<T>& p)
   {
     // @@ Empty maps are not cleaned up by this version of erase.
     //
diff --git a/odb/session.txx b/odb/session.txx
index ce13970..42aa965 100644
--- a/odb/session.txx
+++ b/odb/session.txx
@@ -7,7 +7,7 @@
 namespace odb
 {
   template <typename T>
-  typename session::object_position<T> session::
+  typename session::position<T> session::
   insert (database_type& db,
           const typename object_traits<T>::id_type& id,
           const typename object_traits<T>::pointer_type& obj)
@@ -33,7 +33,7 @@ namespace odb
     if (!r.second)
       r.first->second = obj;
 
-    return object_position<T> (om, r.first);
+    return position<T> (om, r.first);
   }
 
   template <typename T>
-- 
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