From 1f217e38f7507758da1d33d46e675e801621aa38 Mon Sep 17 00:00:00 2001
From: Michael Shepanski <michael@codesynthesis.com>
Date: Thu, 30 Oct 2014 15:21:32 +1100
Subject: Allow lambdas & std::functions as query factories with C++-98 builds
 of libodb

---
 odb/schema-catalog.hxx | 164 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 144 insertions(+), 20 deletions(-)

(limited to 'odb/schema-catalog.hxx')

diff --git a/odb/schema-catalog.hxx b/odb/schema-catalog.hxx
index 7d675fe..510126a 100644
--- a/odb/schema-catalog.hxx
+++ b/odb/schema-catalog.hxx
@@ -13,7 +13,9 @@
 #include <cstddef> // std::size_t
 
 #ifdef ODB_CXX11
-#  include <functional> // std::function
+#  include <utility>     // std::move
+#  include <functional>  // std::function
+#  include <type_traits> // std::enable_if, std::is_convertible
 #endif
 
 #include <odb/forward.hxx> // schema_version, odb::core
@@ -74,11 +76,11 @@ namespace odb
                   schema_version = 0,
                   const std::string& name = "");
 
-#ifdef ODB_CXX11
-    typedef std::function<void (database&)> data_migration_function_type;
-#else
-    typedef void (*data_migration_function_type) (database&);
-#endif
+    typedef void data_migration_function_type (database&);
+    typedef data_migration_function_type* data_migration_function_ptr;
+
+    typedef details::function_wrapper<data_migration_function_type>
+    data_migration_function_wrapper;
 
     // The following three variants of the registration functions make
     // sure that the version is greater that the base model version.
@@ -87,38 +89,59 @@ namespace odb
     //
     // Data migration functions are called in the order of registration.
     //
+#ifndef ODB_CXX11
     template <schema_version v, schema_version base>
     static void
-    data_migration_function (data_migration_function_type f,
+    data_migration_function (data_migration_function_ptr f,
                              const std::string& name = "")
     {
       data_migration_function<v, base> (id_common, f, name);
     }
 
+#else
+    template <schema_version v, schema_version base, typename F>
+    static typename std::enable_if<
+      std::is_convertible<
+        F, std::function<data_migration_function_type>>::value, void>::type
+    data_migration_function (F f, const std::string& name = "")
+    {
+      data_migration_function<v, base> (id_common, std::move (f), name);
+    }
+#endif
+
     // Database-specific data migration.
     //
+#ifndef ODB_CXX11
     template <schema_version v, schema_version base>
     static void
     data_migration_function (database& db,
-                             data_migration_function_type f,
+                             data_migration_function_ptr f,
                              const std::string& name = "")
     {
       data_migration_function<v, base> (db.id (), f, name);
     }
+#else
+    template <schema_version v, schema_version base, typename F>
+    static typename std::enable_if<
+      std::is_convertible<
+        F, std::function<data_migration_function_type>>::value, void>::type
+    data_migration_function (database& db, F f, const std::string& name = "")
+    {
+      data_migration_function<v, base> (db.id (), std::move (f), name);
+    }
+#endif
 
+#ifndef ODB_CXX11
     template <schema_version v, schema_version base>
     static void
     data_migration_function (database_id id,
-                             data_migration_function_type f,
+                             data_migration_function_ptr f,
                              const std::string& name = "")
     {
       // If the data migration version is below the base model version
       // then it will never be called.
       //
-#ifdef ODB_CXX11
-      static_assert (v > base || base == 0,
-                     "data migration function is no longer necessary");
-#else
+
       // Poor man's static_assert.
       //
       typedef details::meta::static_assert_test<(v > base || base == 0)>
@@ -126,36 +149,109 @@ namespace odb
 
       char sa [sizeof (data_migration_function_is_no_longer_necessary)];
       ODB_POTENTIALLY_UNUSED (sa);
-#endif
 
       data_migration_function (id, v, f, name);
     }
+#else
+    template <schema_version v, schema_version base, typename F>
+    static typename std::enable_if<
+      std::is_convertible<
+        F, std::function<data_migration_function_type>>::value, void>::type
+    data_migration_function (database_id id, F f, const std::string& name = "")
+    {
+      // If the data migration version is below the base model version
+      // then it will never be called.
+      //
+      static_assert (v > base || base == 0,
+                     "data migration function is no longer necessary");
+
+      data_migration_function (id, v, std::move (f), name);
+    }
+#endif
 
     // The same as above but take the version as an argument and do
     // not check whether it is greater than the base model version.
     //
+#ifndef ODB_CXX11
     static void
     data_migration_function (schema_version v,
-                             data_migration_function_type f,
+                             data_migration_function_ptr f,
                              const std::string& name = "")
     {
       data_migration_function (id_common, v, f, name);
     }
+#else
+    template <typename F>
+    static typename std::enable_if<
+      std::is_convertible<
+        F, std::function<data_migration_function_type>>::value, void>::type
+    data_migration_function (schema_version v,
+                             F f,
+                             const std::string& name = "")
+    {
+      data_migration_function (id_common, v, std::move (f), name);
+    }
+#endif
 
+#ifndef ODB_CXX11
     static void
     data_migration_function (database& db,
                              schema_version v,
-                             data_migration_function_type f,
+                             data_migration_function_ptr f,
                              const std::string& name = "")
     {
       data_migration_function (db.id (), v, f, name);
     }
+#else
+    template <typename F>
+    static typename std::enable_if<
+      std::is_convertible<
+        F, std::function<data_migration_function_type>>::value, void>::type
+    data_migration_function (database& db,
+                             schema_version v,
+                             F f,
+                             const std::string& name = "")
+    {
+      data_migration_function (db.id (), v, std::move (f), name);
+    }
+#endif
+
+#ifndef ODB_CXX11
+    static void
+    data_migration_function (database_id i,
+                             schema_version v,
+                             data_migration_function_ptr f,
+                             const std::string& name = "")
+    {
+      data_migration_function (i,
+                               v,
+                               data_migration_function_wrapper (f),
+                               name);
+    }
+#else
+    template <typename F>
+    static typename std::enable_if<
+      std::is_convertible<
+        F, std::function<data_migration_function_type>>::value, void>::type
+    data_migration_function (database_id i,
+                             schema_version v,
+                             F f,
+                             const std::string& name = "")
+    {
+      data_migration_function (
+        i,
+        v,
+        data_migration_function_wrapper (std::move (f)),
+        name);
+    }
+#endif
 
+  private:
     static void
     data_migration_function (database_id,
                              schema_version,
-                             data_migration_function_type,
-                             const std::string& name = "");
+                             data_migration_function_wrapper,
+                             const std::string& name);
 
     // Combined schema and data migration.
     //
@@ -244,17 +340,45 @@ namespace odb
   {
     typedef schema_catalog::data_migration_function_type function_type;
 
-    data_migration_entry (function_type f, const std::string& name = "")
+#ifndef ODB_CXX11
+    data_migration_entry (function_type* f, const std::string& name = "")
     {
       schema_catalog::data_migration_function<v, base> (f, name);
     }
+#else
+    template <typename F>
+    data_migration_entry (F f,
+                          const std::string& name = "",
+                          typename std::enable_if<std::is_convertible<
+                            F, std::function<function_type>>::value>
+                          ::type* = 0)
+    {
+      schema_catalog::data_migration_function<v, base> (std::move (f), name);
+    }
+#endif
 
+#ifndef ODB_CXX11
     data_migration_entry (database_id id,
-                          function_type f,
+                          function_type *f,
                           const std::string& name = "")
     {
       schema_catalog::data_migration_function<v, base> (id, v, f, name);
     }
+#else
+    template <typename F>
+    data_migration_entry (database_id id,
+                          F f,
+                          const std::string& name = "",
+                          typename std::enable_if<std::is_convertible<
+                            F, std::function<function_type>>::value>
+                          ::type* = 0)
+    {
+      schema_catalog::data_migration_function<v, base> (id,
+                                                        v,
+                                                        std::move (f),
+                                                        name);
+    }
+#endif
   };
 
   namespace common
-- 
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