Implement support for database operations callbacks

New object pragma: callback. New test: common/callback. New manual
section: 10.1.4, "callback".

3 files changed, 48 insertions, 8 deletions

diff --git a/odb/mysql/object-statements.hxx b/odb/mysql/object-statements.hxx
index e5f6489..c341352 100644
--- a/odb/mysql/object-statements.hxx
+++ b/odb/mysql/object-statements.hxx
@@ -362,6 +362,28 @@ namespace odb
 
       typedef std::vector<delayed_load> delayed_loads;
       delayed_loads delayed_;
+
+      // Delayed vectors swap guard. See the load_delayed_() function for
+      // details.
+      //
+      struct swap_guard
+      {
+        swap_guard (object_statements& os, delayed_loads& dl)
+            : os_ (os), dl_ (dl)
+        {
+          dl_.swap (os_.delayed_);
+        }
+
+        ~swap_guard ()
+        {
+          os_.clear_delayed ();
+          dl_.swap (os_.delayed_);
+        }
+
+      private:
+        object_statements& os_;
+        delayed_loads& dl_;
+      };
     };
   }
 }
diff --git a/odb/mysql/object-statements.txx b/odb/mysql/object-statements.txx
index 46c8ab0..f98f11d 100644
--- a/odb/mysql/object-statements.txx
+++ b/odb/mysql/object-statements.txx
@@ -7,6 +7,7 @@
 #include <cstring> // std::memset
 
 #include <odb/session.hxx>
+#include <odb/callback.hxx>
 #include <odb/exceptions.hxx>
 
 #include <odb/mysql/connection.hxx>
@@ -43,22 +44,34 @@ namespace odb
     void object_statements<T>::
     load_delayed_ ()
     {
-      // We should be careful here: the delayed vector can change
-      // from under us as a result of a recursive load.
-      //
       database& db (connection ().database ());
 
-      while (!delayed_.empty ())
+      delayed_loads dls;
+      swap_guard sg (*this, dls);
+
+      while (!dls.empty ())
       {
-        delayed_load l (delayed_.back ());
+        delayed_load l (dls.back ());
         typename object_cache_traits::insert_guard g (l.pos);
-        delayed_.pop_back ();
+        dls.pop_back ();
 
         if (!object_traits::find_ (*this, l.id))
           throw object_not_persistent ();
 
+        object_traits::callback (db, *l.obj, callback_event::pre_load);
+
+        // Our calls to init/load below can result in additional delayed
+        // loads being added to the delayed_ vector. We need to process
+        // those before we call the post callback.
+        //
         object_traits::init (*l.obj, image (), db);
         object_traits::load_ (*this, *l.obj); // Load containers, etc.
+
+        if (!delayed_.empty ())
+          load_delayed_ ();
+
+        object_traits::callback (db, *l.obj, callback_event::post_load);
+
         g.release ();
       }
     }
diff --git a/odb/mysql/result.txx b/odb/mysql/result.txx
index f6d0a79..84eb723 100644
--- a/odb/mysql/result.txx
+++ b/odb/mysql/result.txx
@@ -3,6 +3,7 @@
 // copyright : Copyright (c) 2009-2011 Code Synthesis Tools CC
 // license   : GNU GPL v2; see accompanying LICENSE file
 
+#include <odb/callback.hxx>
 #include <odb/exceptions.hxx>
 
 namespace odb
@@ -39,8 +40,11 @@ namespace odb
       assert (!statements_.locked ());
       typename object_statements<object_type>::auto_lock l (statements_);
 
+      odb::database& db (this->database ());
+      object_traits::callback (db, obj, callback_event::pre_load);
+
       typename object_traits::image_type& i (statements_.image ());
-      object_traits::init (obj, i, this->database ());
+      object_traits::init (obj, i, db);
 
       // Initialize the id image and binding and load the rest of the object
       // (containers, etc).
@@ -57,8 +61,9 @@ namespace odb
       }
 
       object_traits::load_ (statements_, obj);
-
       statements_.load_delayed ();
+      object_traits::callback (db, obj, callback_event::post_load);
+
       l.unlock ();
     }