Add odb::connection class

This abstract class represents a connection to the database. One can
use it to start a transaction or to execute a native statement out
of a transaction.

Before we had concrete connection classes in the database runtime
libraries (e.g., odb::mysql::connection). Now these classes derive
from odb::connection.

8 files changed, 160 insertions, 22 deletions

diff --git a/odb/tracer/connection.cxx b/odb/tracer/connection.cxx
new file mode 100644
index 0000000..516e36a
--- /dev/null
+++ b/odb/tracer/connection.cxx
@@ -0,0 +1,37 @@
+// file      : odb/tracer/connection.cxx
+// author    : Boris Kolpackov <boris@codesynthesis.com>
+// copyright : Copyright (c) 2009-2011 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#include <odb/transaction.hxx>
+
+#include <odb/tracer/database.hxx>
+#include <odb/tracer/connection.hxx>
+
+namespace odb
+{
+  namespace tracer
+  {
+    connection::
+    connection (database_type& db)
+        : odb::connection (db)
+    {
+    }
+
+    unsigned long long connection::
+    execute (const char*, std::size_t)
+    {
+      return 0;
+    }
+
+    transaction_impl* connection::
+    begin ()
+    {
+      if (odb::transaction::has_current ())
+        throw already_in_transaction ();
+
+      return new transaction_impl (
+        connection_ptr (inc_ref (this)));
+    }
+  }
+}
diff --git a/odb/tracer/connection.hxx b/odb/tracer/connection.hxx
new file mode 100644
index 0000000..743bf92
--- /dev/null
+++ b/odb/tracer/connection.hxx
@@ -0,0 +1,44 @@
+// file      : odb/tracer/connection.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_TRACER_CONNECTION_HXX
+#define ODB_TRACER_CONNECTION_HXX
+
+#include <odb/pre.hxx>
+
+#include <odb/connection.hxx>
+#include <odb/details/shared-ptr.hxx>
+
+#include <odb/tracer/transaction-impl.hxx>
+#include <odb/tracer/details/export.hxx>
+
+namespace odb
+{
+  namespace tracer
+  {
+    class database;
+
+    class connection;
+    typedef details::shared_ptr<connection> connection_ptr;
+
+    class LIBODB_TRACER_EXPORT connection: public odb::connection
+    {
+    public:
+      typedef tracer::database database_type;
+
+      connection (database_type&);
+
+      virtual unsigned long long
+      execute (const char* statement, std::size_t length);
+
+      virtual transaction_impl*
+      begin ();
+    };
+  }
+}
+
+#include <odb/post.hxx>
+
+#endif // ODB_TRACER_CONNECTION_HXX
diff --git a/odb/tracer/database.cxx b/odb/tracer/database.cxx
index 1359a26..90cfdfd 100644
--- a/odb/tracer/database.cxx
+++ b/odb/tracer/database.cxx
@@ -3,8 +3,8 @@
 // copyright : Copyright (c) 2009-2011 Code Synthesis Tools CC
 // license   : GNU GPL v2; see accompanying LICENSE file
 
-#include <odb/transaction.hxx>
 #include <odb/tracer/database.hxx>
+#include <odb/tracer/connection.hxx>
 
 namespace odb
 {
@@ -15,19 +15,26 @@ namespace odb
     {
     }
 
-    unsigned long long database::
-    execute (const char*, std::size_t)
+    transaction_impl* database::
+    begin ()
     {
-      return 0;
+      return connection ()->begin ();
     }
 
-    transaction_impl* database::
-    begin ()
+    inline connection_ptr database::
+    connection ()
     {
-      if (odb::transaction::has_current ())
-        throw already_in_transaction ();
+      // Go through the virtual connection_() function instead of
+      // directly to allow overriding.
+      //
+      return connection_ptr (
+        static_cast<tracer::connection*> (connection_ ()));
+    }
 
-      return new transaction_impl (*this);
+    odb::connection* database::
+    connection_ ()
+    {
+      return new (details::shared) connection_type (*this);
     }
   }
 }
diff --git a/odb/tracer/database.hxx b/odb/tracer/database.hxx
index 7210681..2468583 100644
--- a/odb/tracer/database.hxx
+++ b/odb/tracer/database.hxx
@@ -9,8 +9,9 @@
 #include <odb/pre.hxx>
 
 #include <odb/database.hxx>
-#include <odb/tracer/transaction-impl.hxx>
 
+#include <odb/tracer/connection.hxx>
+#include <odb/tracer/transaction-impl.hxx>
 #include <odb/tracer/details/export.hxx>
 
 namespace odb
@@ -20,14 +21,20 @@ namespace odb
     class LIBODB_TRACER_EXPORT database: public odb::database
     {
     public:
+      typedef tracer::connection connection_type;
+
       virtual
       ~database ();
 
-      virtual unsigned long long
-      execute (const char* statement, std::size_t length);
-
-      virtual transaction_impl*
+      transaction_impl*
       begin ();
+
+      connection_ptr
+      connection ();
+
+    protected:
+      virtual odb::connection*
+      connection_ ();
     };
   }
 }
diff --git a/odb/tracer/forward.hxx b/odb/tracer/forward.hxx
new file mode 100644
index 0000000..61f0eb7
--- /dev/null
+++ b/odb/tracer/forward.hxx
@@ -0,0 +1,35 @@
+// file      : odb/tracer/forward.hxx
+// author    : Boris Kolpackov <boris@codesynthesis.com>
+// copyright : Copyright (c) 2005-2011 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#ifndef ODB_TRACER_FORWARD_HXX
+#define ODB_TRACER_FORWARD_HXX
+
+#include <odb/pre.hxx>
+
+#include <odb/forward.hxx>
+
+namespace odb
+{
+  namespace tracer
+  {
+    class database;
+    class connection;
+    typedef details::shared_ptr<connection> connection_ptr;
+    class transaction;
+  }
+
+  namespace details
+  {
+    template <>
+    struct counter_type<tracer::connection>
+    {
+      typedef shared_base counter;
+    };
+  }
+}
+
+#include <odb/post.hxx>
+
+#endif // ODB_TRACER_FORWARD_HXX
diff --git a/odb/tracer/makefile b/odb/tracer/makefile
index d7b4611..335e681 100644
--- a/odb/tracer/makefile
+++ b/odb/tracer/makefile
@@ -5,7 +5,12 @@
 
 include $(dir $(lastword $(MAKEFILE_LIST)))../../build/bootstrap.make
 
-cxx := exceptions.cxx database.cxx transaction.cxx transaction-impl.cxx
+cxx :=               \
+exceptions.cxx       \
+database.cxx         \
+connection.cxx       \
+transaction.cxx      \
+transaction-impl.cxx
 
 cxx_tun := $(cxx)
 cxx_obj := $(addprefix $(out_base)/,$(cxx_tun:.cxx=.o))
diff --git a/odb/tracer/transaction-impl.cxx b/odb/tracer/transaction-impl.cxx
index f8b90af..2069568 100644
--- a/odb/tracer/transaction-impl.cxx
+++ b/odb/tracer/transaction-impl.cxx
@@ -6,6 +6,7 @@
 #include <iostream>
 
 #include <odb/tracer/database.hxx>
+#include <odb/tracer/connection.hxx>
 #include <odb/tracer/transaction-impl.hxx>
 
 using std::cout;
@@ -16,8 +17,10 @@ namespace odb
   namespace tracer
   {
     transaction_impl::
-    transaction_impl (database_type& db)
-        : odb::transaction_impl (db), finalized_ (false)
+    transaction_impl (connection_ptr c)
+        : odb::transaction_impl (c->database (), *c),
+          finalized_ (false),
+          connection_ (c)
     {
       cout << "begin transaction" << endl;
     }
diff --git a/odb/tracer/transaction-impl.hxx b/odb/tracer/transaction-impl.hxx
index a4d2b40..f926183 100644
--- a/odb/tracer/transaction-impl.hxx
+++ b/odb/tracer/transaction-impl.hxx
@@ -9,25 +9,24 @@
 #include <odb/pre.hxx>
 
 #include <odb/transaction.hxx>
+#include <odb/details/shared-ptr.hxx>
 
+#include <odb/tracer/forward.hxx>
 #include <odb/tracer/details/export.hxx>
 
 namespace odb
 {
   namespace tracer
   {
-    class database;
-    class transaction;
-
     class LIBODB_TRACER_EXPORT transaction_impl: public odb::transaction_impl
     {
     protected:
-      friend class database;
+      friend class connection;
       friend class transaction;
 
       typedef tracer::database database_type;
 
-      transaction_impl (database_type&);
+      transaction_impl (connection_ptr);
 
       virtual
       ~transaction_impl ();
@@ -40,6 +39,7 @@ namespace odb
 
     private:
       bool finalized_;
+      connection_ptr connection_;
     };
   }
 }