Add support for object sections

Sections are an optimization mechanism that allows the partitioning of
data members of a persistent class into groups that can be separately
loaded and/or updated.

1 files changed, 114 insertions, 0 deletions

diff --git a/odb/section.hxx b/odb/section.hxx
new file mode 100644
index 0000000..e32996c
--- /dev/null
+++ b/odb/section.hxx
@@ -0,0 +1,114 @@
+// file      : odb/section.hxx
+// copyright : Copyright (c) 2009-2013 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#ifndef ODB_SECTION_HXX
+#define ODB_SECTION_HXX
+
+#include <odb/pre.hxx>
+
+#include <odb/transaction.hxx>
+#include <odb/details/export.hxx>
+
+namespace odb
+{
+  class LIBODB_EXPORT section
+  {
+  public:
+    // Load state.
+    //
+    bool
+    loaded () const {return state_.loaded;}
+
+    // Mark a loaded section as not loaded. This, for example, can be
+    // useful if you don't want the section to be reloaded during the
+    // object reload.
+    //
+    void
+    unload ()
+    {
+      state_.loaded = 0;
+      state_.changed = 0;
+      state_.restore = 0;
+    }
+
+    // Change state.
+    //
+    bool
+    changed () const {return state_.changed;}
+
+    // Mark the section as changed.
+    //
+    void
+    change ()
+    {
+      state_.changed = 1;
+      state_.restore = 0;
+    }
+
+    // User data. 4 bits of custom state.
+    //
+    unsigned char
+    user_data () const {return state_.user;}
+
+    void
+    user_data (unsigned char u) {state_.user = u;}
+
+  public:
+    section ()
+    {
+      state_.loaded = 0;
+      state_.changed = 0;
+      state_.armed = 0;
+      state_.restore = 0;
+    }
+
+    ~section ()
+    {
+      if (state_.armed)
+        disarm ();
+    }
+
+    // Implementation details.
+    //
+  public:
+    // Arm the callback and set the restore flag if transaction is not NULL.
+    //
+    void
+    reset (bool l = false, bool c = false, transaction* t = 0) const
+    {
+      state_.loaded = l;
+      state_.changed = c;
+
+      if (t != 0 && !state_.armed)
+      {
+        t->callback_register (&transacion_callback,
+                              const_cast<section*> (this));
+        state_.armed = 1;
+      }
+
+      state_.restore = (t != 0);
+    }
+
+  private:
+    void
+    disarm ();
+
+    static void
+    transacion_callback (unsigned short, void* key, unsigned long long);
+
+  private:
+    mutable struct
+    {
+      unsigned char loaded : 1;
+      unsigned char changed : 1;
+      unsigned char armed : 1;    // Transaction callback is armed.
+      unsigned char restore: 1;   // Restore changed flag on rollback.
+      unsigned char user : 4;     // User data.
+    } state_;
+  };
+}
+
+#include <odb/post.hxx>
+
+#endif // ODB_SECTION_HXX