Allow lambdas & std::functions as query factories with C++-98 builds of libodb

3 files changed, 217 insertions, 0 deletions

diff --git a/odb/details/function-wrapper.hxx b/odb/details/function-wrapper.hxx
new file mode 100644
index 0000000..5615fca
--- /dev/null
+++ b/odb/details/function-wrapper.hxx
@@ -0,0 +1,83 @@
+// file      : odb/details/function-wrapper.hxx
+// copyright : Copyright (c) 2009-2014 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#ifndef ODB_DETAILS_FUNCTION_WRAPPER_HXX
+#define ODB_DETAILS_FUNCTION_WRAPPER_HXX
+
+#include <odb/pre.hxx>
+
+#include <odb/details/config.hxx> // ODB_CXX11
+
+#ifdef ODB_CXX11
+#  include <functional>  // std::function
+#  include <type_traits> // std::enable_if, std::is_convertible
+#endif
+
+namespace odb
+{
+  namespace details
+  {
+    // Low-level 'callable object' wrapper similar to std::function but
+    // that works in both C++98 and 11. In particular, the call site can
+    // be compiled in C++98 and the registration site in C++11 and it
+    // will work.
+    //
+    template <typename F>
+    struct function_wrapper
+    {
+      ~function_wrapper ();
+
+      explicit
+      function_wrapper (F* = 0);
+
+#ifdef ODB_CXX11
+      typedef typename std::function<F> std_function_type;
+
+      // This overload accepts lambdas and std::functions, but when the
+      // argument is convertible to F*, then we disable it in favor of the
+      // other overload (above), which is more efficient.
+      //
+      // Subtlety alert: if you're thinking of changing this to accept a
+      // std::function<F> argument, stop. That creates an overload ambiguity
+      // when the actual parameter is a lambda, which is convertible to either
+      // std::function<F> or F*.
+      //
+      template <typename F1>
+      function_wrapper(F1,
+                       typename std::enable_if<
+                       !std::is_convertible<F1, F*>::value>::type* = 0);
+#endif
+
+      // Destructive copy construction and assignment (aka move). These
+      // should really only be called by containers when they need to
+      // reallocate the underlying buffer and move the elements.
+      //
+      function_wrapper (const function_wrapper<F>&);
+      function_wrapper&
+      operator= (const function_wrapper<F>&);
+
+      void swap (function_wrapper<F>&);
+
+      // Conversion to bool.
+      //
+    public:
+      typedef void (function_wrapper<F>::*bool_convertible) ();
+      void true_value () {}
+
+      operator bool_convertible () const;
+
+    public:
+      F* function;
+      void (*deleter) (const void*);
+      const void* std_function;
+    };
+  }
+}
+
+#include <odb/details/function-wrapper.ixx>
+#include <odb/details/function-wrapper.txx>
+
+#include <odb/post.hxx>
+
+#endif // ODB_DETAILS_FUNCTION_WRAPPER_HXX
diff --git a/odb/details/function-wrapper.ixx b/odb/details/function-wrapper.ixx
new file mode 100644
index 0000000..58ede04
--- /dev/null
+++ b/odb/details/function-wrapper.ixx
@@ -0,0 +1,47 @@
+// file      : odb/details/function-wrapper.ixx
+// copyright : Copyright (c) 2009-2014 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+namespace odb
+{
+  namespace details
+  {
+    template <typename F>
+    inline function_wrapper<F>::
+    ~function_wrapper ()
+    {
+      if (deleter != 0)
+        deleter (std_function);
+    }
+
+    template <typename F>
+    inline function_wrapper<F>::
+    function_wrapper (F* f)
+        : function (f), deleter (0), std_function (0)
+    {
+    }
+
+    template <typename F>
+    inline function_wrapper<F>::
+    function_wrapper (const function_wrapper<F>& x)
+        : function (0), deleter (0), std_function (0)
+    {
+      swap (const_cast<function_wrapper<F>&> (x));
+    }
+
+    template <typename F>
+    inline function_wrapper<F>& function_wrapper<F>::
+    operator= (const function_wrapper<F>& x)
+    {
+      swap (const_cast<function_wrapper<F>&> (x));
+      return *this;
+    }
+
+    template <typename F>
+    inline function_wrapper<F>::
+    operator bool_convertible () const
+    {
+      return function != 0 ? &function_wrapper<F>::true_value : 0;
+    }
+  }
+}
diff --git a/odb/details/function-wrapper.txx b/odb/details/function-wrapper.txx
new file mode 100644
index 0000000..70dcb0f
--- /dev/null
+++ b/odb/details/function-wrapper.txx
@@ -0,0 +1,87 @@
+// file      : odb/details/function-wrapper.txx
+// copyright : Copyright (c) 2009-2014 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#include <utility> // std::swap, std::move
+
+namespace odb
+{
+  namespace details
+  {
+#ifdef ODB_CXX11
+    template <typename F>
+    struct caller_impl;
+
+#ifdef ODB_CXX11_VARIADIC_TEMPLATE
+    template <typename R, typename... A>
+    struct caller_impl<R (A...)>
+    {
+      static R
+      function (const void* f, A... a)
+      {
+        return (*static_cast<const std::function<R (A...)>*> (f)) (a...);
+      }
+    };
+#else
+    template <typename R, typename A1>
+    struct caller_impl<R (A1)>
+    {
+      static R
+      function (const void* f, A1 a1)
+      {
+        return (*static_cast<const std::function<R (A1)>*> (f)) (a1);
+      }
+    };
+
+    template <typename R, typename A1, typename A2>
+    struct caller_impl<R (A1, A2)>
+    {
+      static R
+      function (const void* f, A1 a1, A2 a2)
+      {
+        return (*static_cast<const std::function<R (A1, A2)>*> (f)) (a1, a2);
+      }
+    };
+#endif
+
+    template <typename F>
+    void
+    deleter_impl (const void* f)
+    {
+      delete static_cast<const std::function<F>*> (f);
+    }
+
+    template <typename F>
+    template <typename F1>
+    function_wrapper<F>::
+    function_wrapper (
+      F1 f,
+      typename std::enable_if<!std::is_convertible<F1, F*>::value>::type*)
+    {
+      std_function_type sf (std::move (f));
+
+      if (F* const* const f = sf.template target<F*> ())
+      {
+        function = *f;
+        deleter = 0;
+        std_function = 0;
+      }
+      else
+      {
+        function = reinterpret_cast<F*> (&caller_impl<F>::function);
+        deleter = &deleter_impl<F>;
+        std_function = new std_function_type (std::move (sf));
+      }
+    }
+#endif
+
+    template <typename F>
+    void function_wrapper<F>::
+    swap (function_wrapper<F>& x)
+    {
+      std::swap (function, x.function);
+      std::swap (deleter, x.deleter);
+      std::swap (std_function, x.std_function);
+    }
+  }
+}