From 1cc4eb4d11c08f986408c9b671840b6e077b42ff Mon Sep 17 00:00:00 2001
From: Constantin Michael <constantin@codesynthesis.com>
Date: Fri, 28 Oct 2011 14:10:36 +0200
Subject: Implement lob_auto_descriptor

---
 odb/oracle/auto-descriptor.hxx |  4 ++--
 odb/oracle/oracle-types.hxx    | 38 +++++++++++++++++++++++++++++++++++---
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/odb/oracle/auto-descriptor.hxx b/odb/oracle/auto-descriptor.hxx
index a6c82a3..cd537ef 100644
--- a/odb/oracle/auto-descriptor.hxx
+++ b/odb/oracle/auto-descriptor.hxx
@@ -85,11 +85,11 @@ namespace odb
         d_ = d;
       }
 
-    private:
+    protected:
       auto_descriptor (const auto_descriptor&);
       auto_descriptor& operator= (const auto_descriptor&);
 
-    private:
+    protected:
       D* d_;
     };
   }
diff --git a/odb/oracle/oracle-types.hxx b/odb/oracle/oracle-types.hxx
index 7f2c46d..1e94894 100644
--- a/odb/oracle/oracle-types.hxx
+++ b/odb/oracle/oracle-types.hxx
@@ -98,8 +98,7 @@ namespace odb
 
       buffer_type type; // The type stored by buffer.
       void* buffer;     // Data buffer pointer. When result callbacks are in
-                        // use, this is interpreted as an
-                        // auto_descriptor<OCILobLocator>*.
+                        // use, this is interpreted as an lob_auto_descriptor*.
       ub2* size;        // The number of bytes in buffer. When parameter
                         // callbacks are in use, this is interpreted as a ub4*
                         // indicating the current position.
@@ -117,7 +116,7 @@ namespace odb
 
     // An instance of this structure specifies the function to invoke and
     // the context to pass just prior to the image associated with a query
-    // is modified.
+    // being modified.
     //
     struct change_callback
     {
@@ -126,6 +125,39 @@ namespace odb
       void (*callback) (void*);
       void* context;
     };
+
+    // The LOB specialization of auto_descriptor allows for transparent
+    // transferal of LOB descriptors between auto_descriptor instances. This
+    // simplifies the implementation of a private copy of the shared image
+    // associated with queries.
+    //
+    class LIBODB_ORACLE_EXPORT lob_auto_descriptor
+      : auto_descriptor<OCILobLocator>
+    {
+    public:
+      lob_auto_descriptor (OCILobLocator* l = 0)
+        : auto_descriptor<OCILobLocator> (l)
+      {
+      }
+
+      lob_auto_descriptor (lob_auto_descriptor& x)
+        : auto_descriptor<OCILobLocator> (0)
+      {
+        OCILobLocator* l (x.d_);
+        x.d_ = 0;
+        reset (l);
+      }
+
+      lob_auto_descriptor&
+      operator= (lob_auto_descriptor& x)
+      {
+        OCILobLocator* l (x.d_);
+        x.d_ = 0;
+        reset (l);
+
+        return *this;
+      }
+    };
   }
 }
 
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