Implement traits

3 files changed, 755 insertions, 380 deletions

diff --git a/odb/oracle/makefile b/odb/oracle/makefile
index 0725800..bd8d8cb 100644
--- a/odb/oracle/makefile
+++ b/odb/oracle/makefile
@@ -16,6 +16,7 @@ exceptions.cxx           \
 object-statements.cxx    \
 statement.cxx            \
 statements-base.cxx      \
+traits.cxx               \
 transaction.cxx          \
 transaction-impl.cxx     \
 details/number.cxx
diff --git a/odb/oracle/traits.cxx b/odb/oracle/traits.cxx
index 16bfdee..6cf55c8 100644
--- a/odb/oracle/traits.cxx
+++ b/odb/oracle/traits.cxx
@@ -3,4 +3,163 @@
 // copyright : Copyright (c) 2005-2011 Code Synthesis Tools CC
 // license   : ODB NCUEL; see accompanying LICENSE file
 
+#include <cstddef> // std::size_t
+#include <cstring> // std::memcpy, std::strlen
+#include <cassert>
+
 #include <odb/oracle/traits.hxx>
+
+using namespace std;
+
+namespace odb
+{
+  namespace oracle
+  {
+    //
+    // string_value_traits
+    //
+
+    void string_value_traits::
+    set_image (char* b,
+               size_t c,
+               size_t& n,
+               bool& is_null,
+               const string& v)
+    {
+      is_null = false;
+      n = v.size ();
+
+      assert (n <= c);
+
+      if (n != 0 && n <= c)
+        memcpy (b, v.c_str (), n);
+    }
+
+    //
+    // c_string_value_traits
+    //
+
+    void c_string_value_traits::
+    set_image (char* b,
+               size_t c,
+               size_t& n,
+               bool& is_null,
+               const char* v)
+    {
+      is_null = false;
+      n = strlen (v);
+
+      assert (n <= c);
+
+      if (n != 0 && n <= c)
+        memcpy (b, v, n);
+    }
+
+    //
+    // string_lob_value_traits
+    //
+
+    bool string_lob_value_traits::
+    param_callback (void* ctx,
+                    ub4* pos_ctx,
+                    void** b,
+                    ub4* s,
+                    chunk_position* p,
+                    void* temp_b,
+                    ub4 cap)
+    {
+      const string& v (*reinterpret_cast<string*> (ctx));
+
+      // @@ We rely on *pos_ctx == 0 for the first call. Make sure that this is
+      // set by the generated code, and update comment in oracle-types.hxx
+      // specifying that this is so.
+      //
+      *s = static_cast<ub4> (v.size ()) - *pos_ctx;
+
+      if (*s <= cap)
+        *p = *pos_ctx == 0 ? one_chunk : last_chunk;
+      else
+      {
+        *p = *pos_ctx == 0 ? first_chunk : next_chunk;
+        *s = cap;
+        *pos_ctx += *s;
+      }
+
+      *b = temp_b;
+      memcpy (temp_b, v.c_str () + *pos_ctx, *s);
+
+      return true;
+    }
+
+    //
+    // c_string_lob_value_traits
+    //
+
+    bool c_string_lob_value_traits::
+    param_callback (void* ctx,
+                    ub4* pos_ctx,
+                    void** b,
+                    ub4* s,
+                    chunk_position* p,
+                    void* temp_b,
+                    ub4 cap)
+    {
+      const char* v (reinterpret_cast<char*> (ctx));
+
+      // @@ We rely on *pos_ctx == 0 for the first call. Make sure that this is
+      // set by the generated code, and update comment in oracle-types.hxx
+      // specifying that this is so.
+      //
+      *s = static_cast<ub4> (strlen (v)) - *pos_ctx;
+
+      if (*s <= cap)
+        *p = *pos_ctx == 0 ? one_chunk : last_chunk;
+      else
+      {
+        *p = *pos_ctx == 0 ? first_chunk : next_chunk;
+        *s = cap;
+        *pos_ctx += *s;
+      }
+
+      *b = temp_b;
+      memcpy (temp_b, v + *pos_ctx, *s);
+
+      return true;
+    }
+
+    //
+    // default_value_traits<std::vector<char>, id_blob>
+    //
+    bool default_value_traits<std::vector<char>, id_blob>::
+    param_callback (void* ctx,
+                    ub4* pos_ctx,
+                    void** b,
+                    ub4* s,
+                    chunk_position* p,
+                    void* temp_b,
+                    ub4 cap)
+    {
+      const value_type& v (*reinterpret_cast<value_type*> (ctx));
+
+      // @@ We rely on *position_context == 0 for the first call. Make sure
+      // that this is set by the generated code and update the comment in
+      // oracle-types.hxx specifying that this is so.
+      //
+      *s = static_cast<ub4> (v.size ()) - *pos_ctx;
+
+      if (*s <= cap)
+        *p = *pos_ctx == 0 ? one_chunk : last_chunk;
+      else
+      {
+        *p = *pos_ctx == 0 ? first_chunk : next_chunk;
+        *s = cap;
+        *pos_ctx += *s;
+      }
+
+      *b = temp_b;
+      memcpy (temp_b, &v[*pos_ctx], *s);
+
+      return true;
+    }
+  }
+}
diff --git a/odb/oracle/traits.hxx b/odb/oracle/traits.hxx
index d3f006d..a05d74f 100644
--- a/odb/oracle/traits.hxx
+++ b/odb/oracle/traits.hxx
@@ -49,57 +49,152 @@ namespace odb
 
       id_blob,
       id_clob,
-      id_nclob,
+      id_nclob
+    };
+
+    //
+    // int_traits
+    //
+
+    // Only mark fundamental unsigned integers as unsigned. In particular,
+    // treat enums as signed since in most cases and on most platforms the
+    // underlying integer type will be signed. On Windows with VC9 and up
+    // and with GCC, the __intN types are simply aliases for the respective
+    // standard integers so the below code will cover them as well. Also
+    // note that the ODB compiler performs a similar test, so if you change
+    // anything below you will probably also need to make a similar change
+    // there.
+    //
+    template <typename T>
+    struct int_traits {static const bool unsign = false;};
+
+    template <>
+    struct int_traits<bool> {static const bool unsign = true;};
+    template <>
+    struct int_traits<unsigned char> {static const bool unsign = true;};
+    template <>
+    struct int_traits<unsigned short> {static const bool unsign = true;};
+    template <>
+    struct int_traits<unsigned int> {static const bool unsign = true;};
+    template <>
+    struct int_traits<unsigned long> {static const bool unsign = true;};
+    template <>
+    struct int_traits<unsigned long long>
+    {
+      static const bool unsign = true;
     };
 
     //
     // image_traits
     //
 
-    template <database_type_id>
+    template <typename T, database_type_id>
     struct image_traits;
 
-    template <>
-    struct image_traits<id_int32> {typedef int image_type;};
+    // int32
+    //
+    template <bool unsign>
+    struct int32_image_traits;
 
     template <>
-    struct image_traits<id_int64> {typedef unsigned char[12] image_type;};
+    struct int32_image_traits<false>
+    {
+      typedef int image_type;
+    };
 
     template <>
-    struct image_traits<id_big_int> {typedef unsigned char[21] image_type;};
+    struct int32_image_traits<true>
+    {
+      typedef unsigned int image_type;
+    };
 
-    template <>
-    struct image_traits<id_float> {typedef float image_type;};
+    template <typename T>
+    struct image_traits<T, id_int32>: int32_image_traits<int_traits<T>::unsign>
+    {
+    };
 
-    template <>
-    struct image_traits<id_double> {typedef double image_type;};
+    // int64
+    //
+    template <bool unsign>
+    struct int64_image_traits;
 
     template <>
-    struct image_traits<id_big_float> {typedef unsigned char[21] image_type;};
+    struct int64_image_traits<false>
+    {
+      typedef long long image_type;
+    };
 
     template <>
-    struct image_traits<id_date> {typedef unsigned char[7] image_type;};
+    struct int64_image_traits<true>
+    {
+      typedef unsigned long long image_type;
+    };
 
-    template <>
-    struct image_traits<id_timestamp> {typedef unsigned char* image_type;};
+    template <typename T>
+    struct image_traits<T, id_int64>: int64_image_traits<int_traits<T>::unsign>
+    {
+    };
 
-    template <>
-    struct image_traits<id_string> {typedef char* image_type;};
+    // big_int
+    //
+    template <typename T>
+    struct image_traits<T, id_big_int>
+    {
+      // Image is a buffer containing native OCI NUMBER representation.
+      //
+      typedef char* image_type;
+    };
 
-    template <>
-    struct image_traits<id_nstring> {typedef char* image_type;};
+    template <typename T>
+    struct image_traits<T, id_float> {typedef float image_type;};
 
-    template <>
-    struct image_traits<id_raw> {typedef char* image_type;};
+    template <typename T>
+    struct image_traits<T, id_double> {typedef double image_type;};
 
-    template <>
-    struct image_traits<id_blob> {typedef lob_callback image_type;};
+    template <typename T>
+    struct image_traits<T, id_big_float>
+    {
+      // Image is a buffer containing the native OCI NUMBER representation.
+      //
+      typedef char* image_type;
+    };
 
-    template <>
-    struct image_traits<id_clob> {typedef lob_callback image_type;};
+    template <typename T>
+    struct image_traits<T, id_date>
+    {
+      // Image is a buffer containing the native OCI DATE representation. This
+      // buffer has a fixed length of 7 bytes.
+      //
+      typedef char* image_type;
+    };
 
-    template <>
-    struct image_traits<id_nclob> {typedef lob_callback image_type;};
+    template <typename T>
+    struct image_traits<T, id_timestamp>
+    {
+      // Image is a buffer containing the native OCI TIMESTAMP representation.
+      // This buffer has varying length, depending on the microsecond
+      // precision of the TIMESTAMP value.
+      //
+      typedef char* image_type;
+    };
+
+    template <typename T>
+    struct image_traits<T, id_string> {typedef char* image_type;};
+
+    template <typename T>
+    struct image_traits<T, id_nstring> {typedef char* image_type;};
+
+    template <typename T>
+    struct image_traits<T, id_raw> {typedef char* image_type;};
+
+    template <typename T>
+    struct image_traits<T, id_blob> {typedef lob_callback image_type;};
+
+    template <typename T>
+    struct image_traits<T, id_clob> {typedef lob_callback image_type;};
+
+    template <typename T>
+    struct image_traits<T, id_nclob> {typedef lob_callback image_type;};
 
     //
     // value_traits
@@ -114,360 +209,480 @@ namespace odb
     template <typename T, database_type_id, bool w = details::wrapper_p<T>::r>
     struct select_traits;
 
-    // template <typename T, database_type_id ID>
-    // struct select_traits<T, ID, false>
-    // {
-    //   typedef default_value_traits<T, ID> type;
-    // };
-
-    // template <typename W, database_type_id ID>
-    // struct select_traits<W, ID, true>
-    // {
-    //   typedef
-    //   wrapped_value_traits<W, ID, wrapper_traits<W>::null_handler>
-    //   type;
-    // };
-
-    // template <typename T, database_type_id ID>
-    // class value_traits: public select_traits<T, ID>::type
-    // {
-    // };
-
-    // // The wrapped_value_traits specializations should be able to handle
-    // // any value type which means we have to have every possible signature
-    // // of the set_value() and set_image() functions.
-    // //
-    // template <typename W, database_type_id ID>
-    // struct wrapped_value_traits<W, ID, false>
-    // {
-    //   typedef wrapper_traits<W> wtraits;
-    //   typedef typename wtraits::wrapped_type wrapped_type;
-
-    //   typedef W value_type;
-    //   typedef wrapped_type query_type;
-    //   typedef typename image_traits<ID>::image_type image_type;
-
-    //   typedef value_traits<wrapped_type, ID> vtraits;
-
-    //   static void
-    //   set_value (W& v, const image_type& i, bool is_null)
-    //   {
-    //     vtraits::set_value (wtraits::set_ref (v), i, is_null);
-    //   }
-
-    //   static void
-    //   set_image (image_type& i, bool& is_null, const W& v)
-    //   {
-    //     vtraits::set_image (i, is_null, wtraits::get_ref (v));
-    //   }
-
-    //   // String, BLOB, ENUM, and SET.
-    //   //
-    //   static void
-    //   set_value (W& v, const details::buffer& b, std::size_t n, bool is_null)
-    //   {
-    //     vtraits::set_value (wtraits::set_ref (v), b, n, is_null);
-    //   }
-
-    //   static void
-    //   set_image (details::buffer& b, std::size_t& n, bool& is_null, const W& v)
-    //   {
-    //     vtraits::set_image (b, n, is_null, wtraits::get_ref (v));
-    //   }
-
-    //   // BIT.
-    //   //
-    //   static void
-    //   set_value (W& v, const unsigned char* i, std::size_t n, bool is_null)
-    //   {
-    //     vtraits::set_value (wtraits::set_ref (v), i, n, is_null);
-    //   }
-
-    //   static void
-    //   set_image (unsigned char* i,
-    //              std::size_t c,
-    //              std::size_t& n,
-    //              bool& is_null,
-    //              const W& v)
-    //   {
-    //     vtraits::set_image (i, c, n, is_null, wtraits::get_ref (v));
-    //   }
-    // };
-
-    // template <typename W, database_type_id ID>
-    // struct wrapped_value_traits<W, ID, true>
-    // {
-    //   typedef wrapper_traits<W> wtraits;
-    //   typedef typename wtraits::wrapped_type wrapped_type;
-
-    //   typedef W value_type;
-    //   typedef wrapped_type query_type;
-    //   typedef typename image_traits<ID>::image_type image_type;
-
-    //   typedef value_traits<wrapped_type, ID> vtraits;
-
-    //   static void
-    //   set_value (W& v, const image_type& i, bool is_null)
-    //   {
-    //     if (is_null)
-    //       wtraits::set_null (v);
-    //     else
-    //       vtraits::set_value (wtraits::set_ref (v), i, is_null);
-    //   }
-
-    //   static void
-    //   set_image (image_type& i, bool& is_null, const W& v)
-    //   {
-    //     is_null = wtraits::get_null (v);
-
-    //     if (!is_null)
-    //       vtraits::set_image (i, is_null, wtraits::get_ref (v));
-    //   }
-
-    //   // String, BLOB, ENUM, and SET.
-    //   //
-    //   static void
-    //   set_value (W& v, const details::buffer& b, std::size_t n, bool is_null)
-    //   {
-    //     if (is_null)
-    //       wtraits::set_null (v);
-    //     else
-    //       vtraits::set_value (wtraits::set_ref (v), b, n, is_null);
-    //   }
-
-    //   static void
-    //   set_image (details::buffer& b, std::size_t& n, bool& is_null, const W& v)
-    //   {
-    //     is_null = wtraits::get_null (v);
-
-    //     if (!is_null)
-    //       vtraits::set_image (b, n, is_null, wtraits::get_ref (v));
-    //   }
-
-    //   // BIT.
-    //   //
-    //   static void
-    //   set_value (W& v, const unsigned char* i, std::size_t n, bool is_null)
-    //   {
-    //     if (is_null)
-    //       wtraits::set_null (v);
-    //     else
-    //       vtraits::set_value (wtraits::set_ref (v), i, n, is_null);
-    //   }
-
-    //   static void
-    //   set_image (unsigned char* i,
-    //              std::size_t c,
-    //              std::size_t& n,
-    //              bool& is_null,
-    //              const W& v)
-    //   {
-    //     is_null = wtraits::get_null (v);
-
-    //     if (!is_null)
-    //       vtraits::set_image (i, c, n, is_null, wtraits::get_ref (v));
-    //   }
-    // };
-
-    // template <typename T, database_type_id ID>
-    // struct default_value_traits
-    // {
-    //   typedef T value_type;
-    //   typedef T query_type;
-    //   typedef typename image_traits<ID>::image_type image_type;
-
-    //   static void
-    //   set_value (T& v, const image_type& i, bool is_null)
-    //   {
-    //     if (!is_null)
-    //       v = T (i);
-    //     else
-    //       v = T ();
-    //   }
-
-    //   static void
-    //   set_image (image_type& i, bool& is_null, T v)
-    //   {
-    //     is_null = false;
-    //     i = image_type (v);
-    //   }
-    // };
-
-    // // Specialization for numeric enum representations (C++ enum, integer
-    // // types, etc). In particular, this specialization works only for C++
-    // // enum type as long as its numeric value space starts with 0, is
-    // // ascending and contiguous (i.e., the default enumerator assignment).
-    // //
-    // template <typename T>
-    // struct default_value_traits<T, id_enum>
-    // {
-    //   typedef T value_type;
-    //   typedef T query_type;
-    //   typedef unsigned short image_type;
-
-    //   static void
-    //   set_value (T& v, unsigned short i, bool is_null)
-    //   {
-    //     // In MySQL first enumerator has index 1.
-    //     //
-    //     if (!is_null)
-    //       v = static_cast<T> (i - 1);
-    //     else
-    //       v = T ();
-    //   }
-
-    //   static void
-    //   set_image (unsigned short& i, bool& is_null, const T& v)
-    //   {
-    //     is_null = false;
-    //     i = static_cast<unsigned short> (v) + 1;
-    //   }
-    // };
-
-    // // std::string specialization.
-    // //
-    // class LIBODB_MYSQL_EXPORT string_value_traits
-    // {
-    // public:
-    //   typedef std::string value_type;
-    //   typedef std::string query_type;
-    //   typedef details::buffer image_type;
-
-    //   static void
-    //   set_value (std::string& v,
-    //              const details::buffer& b,
-    //              std::size_t n,
-    //              bool is_null)
-    //   {
-    //     if (!is_null)
-    //       v.assign (b.data (), n);
-    //     else
-    //       v.erase ();
-    //   }
-
-    //   static void
-    //   set_image (details::buffer&,
-    //              std::size_t& n,
-    //              bool& is_null,
-    //              const std::string&);
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<std::string, id_string>:
-    //   string_value_traits
-    // {
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<std::string, id_decimal>:
-    //   string_value_traits
-    // {
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<std::string, id_enum>:
-    //   string_value_traits
-    // {
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<std::string, id_set>:
-    //   string_value_traits
-    // {
-    // };
-
-    // // const char* specialization
-    // //
-    // // Specialization for const char* which only supports initialization
-    // // of an image from the value but not the other way around. This way
-    // // we can pass such values to the queries.
-    // //
-    // class LIBODB_MYSQL_EXPORT c_string_value_traits
-    // {
-    // public:
-    //   typedef const char* value_type;
-    //   typedef const char* query_type;
-    //   typedef details::buffer image_type;
-
-    //   static void
-    //   set_image (details::buffer&,
-    //              std::size_t& n,
-    //              bool& is_null,
-    //              const char*);
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<const char*, id_string>:
-    //   c_string_value_traits
-    // {
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<const char*, id_decimal>:
-    //   c_string_value_traits
-    // {
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<const char*, id_enum>:
-    //   c_string_value_traits
-    // {
-    // };
-
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<const char*, id_set>:
-    //   c_string_value_traits
-    // {
-    // };
-
-    // template <std::size_t n>
-    // struct default_value_traits<char[n], id_string>: c_string_value_traits
-    // {
-    // };
-
-    // template <std::size_t n>
-    // struct default_value_traits<char[n], id_decimal>: c_string_value_traits
-    // {
-    // };
-
-    // template <std::size_t n>
-    // struct default_value_traits<char[n], id_enum>: c_string_value_traits
-    // {
-    // };
-
-    // template <std::size_t n>
-    // struct default_value_traits<char[n], id_set>: c_string_value_traits
-    // {
-    // };
-
-    // // std::vector<char> (buffer) specialization.
-    // //
-    // template <>
-    // struct LIBODB_MYSQL_EXPORT default_value_traits<std::vector<char>, id_blob>
-    // {
-    // public:
-    //   typedef std::vector<char> value_type;
-    //   typedef std::vector<char> query_type;
-    //   typedef details::buffer image_type;
-
-    //   static void
-    //   set_value (value_type& v,
-    //              const details::buffer& b,
-    //              std::size_t n,
-    //              bool is_null)
-    //   {
-    //     if (!is_null)
-    //       v.assign (b.data (), b.data () + n);
-    //     else
-    //       v.clear ();
-    //   }
-
-    //   static void
-    //   set_image (details::buffer&,
-    //              std::size_t& n,
-    //              bool& is_null,
-    //              const value_type&);
-    // };
+    template <typename T, database_type_id ID>
+    struct select_traits<T, ID, false>
+    {
+      typedef default_value_traits<T, ID> type;
+    };
+
+    template <typename W, database_type_id ID>
+    struct select_traits<W, ID, true>
+    {
+      typedef
+      wrapped_value_traits<W, ID, wrapper_traits<W>::null_handler>
+      type;
+    };
+
+    template <typename T, database_type_id ID>
+    class value_traits: public select_traits<T, ID>::type
+    {
+    };
+
+    // The wrapped_value_traits specializations should be able to handle
+    // any value type which means we have to have every possible signature
+    // of the set_value() and set_image() functions.
+    //
+    template <typename W, database_type_id ID>
+    struct wrapped_value_traits<W, ID, false>
+    {
+      typedef wrapper_traits<W> wtraits;
+      typedef typename wtraits::wrapped_type wrapped_type;
+
+      typedef W value_type;
+      typedef wrapped_type query_type;
+      typedef typename image_traits<wrapped_type, ID>::image_type image_type;
+
+      typedef value_traits<wrapped_type, ID> vtraits;
+
+      static void
+      set_value (W& v, const image_type& i, bool is_null)
+      {
+        vtraits::set_value (wtraits::set_ref (v), i, is_null);
+      }
+
+      static void
+      set_image (image_type& i, bool& is_null, const W& v)
+      {
+        vtraits::set_image (i, is_null, wtraits::get_ref (v));
+      }
+
+      // big_int, big_float, timestamp, string, nstring, raw.
+      //
+      static void
+      set_value (W& v, const char* i, std::size_t n, bool is_null)
+      {
+        vtraits::set_value (wtraits::set_ref (v), i, n, is_null);
+      }
+
+      static void
+      set_image (char* i,
+                 std::size_t c,
+                 std::size_t& n,
+                 bool& is_null,
+                 const W& v)
+      {
+        vtraits::set_image (i, c, n, is_null, wtraits::get_ref (v));
+      }
+
+      // blob, clob, nclob.
+      //
+      static void
+      set_value (W& v, result_callback_type& cb, void*& context, bool is_null)
+      {
+        vtraits::set_value (wtraits::set_ref (v), cb, context, is_null);
+      }
+
+      static void
+      set_image (param_callback_type& cb,
+                 void*& context,
+                 bool& is_null,
+                 const W& v)
+      {
+        vtraits::set_image (cb, context, is_null, wtraits::get_ref (v));
+      }
+    };
+
+    template <typename W, database_type_id ID>
+    struct wrapped_value_traits<W, ID, true>
+    {
+      typedef wrapper_traits<W> wtraits;
+      typedef typename wtraits::wrapped_type wrapped_type;
+
+      typedef W value_type;
+      typedef wrapped_type query_type;
+      typedef typename image_traits<wrapped_type, ID>::image_type image_type;
+
+      typedef value_traits<wrapped_type, ID> vtraits;
+
+      static void
+      set_value (W& v, const image_type& i, bool is_null)
+      {
+        if (is_null)
+          wtraits::set_null (v);
+        else
+          vtraits::set_value (wtraits::set_ref (v), i, is_null);
+      }
+
+      static void
+      set_image (image_type& i, bool& is_null, const W& v)
+      {
+        is_null = wtraits::get_null (v);
+
+        if (!is_null)
+          vtraits::set_image (i, is_null, wtraits::get_ref (v));
+      }
+
+      // big_int, big_float, timestamp, string, nstring, raw.
+      //
+      static void
+      set_value (W& v, const char* i, std::size_t n, bool is_null)
+      {
+        if (is_null)
+          wtraits::set_null (v);
+        else
+          vtraits::set_value (wtraits::set_ref (v), i, n, is_null);
+      }
+
+      static void
+      set_image (char* i,
+                 std::size_t c,
+                 std::size_t& n,
+                 bool& is_null,
+                 const W& v)
+      {
+        is_null = wtraits::get_null (v);
+
+        if (!is_null)
+          vtraits::set_image (i, c, n, is_null, wtraits::get_ref (v));
+      }
+
+      // blob, clob, nclob.
+      //
+      static void
+      set_value (W& v, result_callback_type& cb, void*& context, bool is_null)
+      {
+        if (is_null)
+          wtraits::set_null (v);
+        else
+          vtraits::set_value (wtraits::set_ref (v), cb, context, is_null);
+      }
+
+      static void
+      set_image (param_callback_type& cb,
+                 void*& context,
+                 bool& is_null,
+                 const W& v)
+      {
+        is_null = wtraits::get_null (v);
+
+        if (!is_null)
+          vtraits::set_image (cb, context, is_null, wtraits::get_ref (v));
+      }
+    };
+
+    template <typename T, database_type_id ID>
+    struct default_value_traits
+    {
+      typedef T value_type;
+      typedef T query_type;
+      typedef typename image_traits<T, ID>::image_type image_type;
+
+      static void
+      set_value (T& v, const image_type& i, bool is_null)
+      {
+        if (!is_null)
+          v = T (i);
+        else
+          v = T ();
+      }
+
+      static void
+      set_image (image_type& i, bool& is_null, T v)
+      {
+        is_null = false;
+        i = image_type (v);
+      }
+    };
+
+    // std::string specialization.
+    //
+    class LIBODB_ORACLE_EXPORT string_value_traits
+    {
+    public:
+      typedef std::string value_type;
+      typedef std::string query_type;
+      typedef char* image_type;
+
+      static void
+      set_value (std::string& v,
+                 const char* b,
+                 std::size_t n,
+                 bool is_null)
+      {
+        if (!is_null)
+          v.assign (b, n);
+        else
+          v.erase ();
+      }
+
+      static void
+      set_image (char*,
+                 std::size_t c,
+                 std::size_t& n,
+                 bool& is_null,
+                 const std::string&);
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<std::string, id_string>:
+      string_value_traits
+    {
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<std::string, id_nstring>:
+      string_value_traits
+    {
+    };
+
+    // const char* specialization.
+    //
+    // Specialization for const char* which only supports initialization
+    // of an image from the value but not the other way around. This way
+    // we can pass such values to the queries.
+    //
+    class LIBODB_ORACLE_EXPORT c_string_value_traits
+    {
+    public:
+      typedef const char* value_type;
+      typedef const char* query_type;
+      typedef char* image_type;
+
+      static void
+      set_image (char*,
+                 std::size_t c,
+                 std::size_t& n,
+                 bool& is_null,
+                 const char*);
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<const char*, id_string>:
+      c_string_value_traits
+    {
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<const char*, id_nstring>:
+      c_string_value_traits
+    {
+    };
+
+    template <std::size_t n>
+    struct default_value_traits<char[n], id_string>: c_string_value_traits
+    {
+    };
+
+    template <std::size_t n>
+    struct default_value_traits<char[n], id_nstring>: c_string_value_traits
+    {
+    };
+
+    // std::string specialization for LOBs.
+    //
+    class string_lob_value_traits
+    {
+    public:
+      typedef std::string value_type;
+      typedef std::string query_type;
+      typedef lob_callback image_type;
+
+      static void
+      set_value (std::string& v,
+                 result_callback_type& cb,
+                 void*& context,
+                 bool is_null)
+      {
+        if (!is_null)
+        {
+          cb = &result_callback;
+          context = &v;
+        }
+        else
+          v.erase ();
+      }
+
+      static void
+      set_image (param_callback_type& cb,
+                 void*& context,
+                 bool& is_null,
+                 const std::string& v)
+      {
+        is_null = false;
+        cb = &param_callback;
+        context = const_cast<std::string*> (&v);
+      }
+
+      static bool
+      result_callback (void* context, void* buffer, ub4 size, chunk_position p)
+      {
+        std::string& v (*reinterpret_cast<std::string*> (context));
+
+        switch (p)
+        {
+        case one_chunk:
+        case first_chunk:
+          {
+            v.clear ();
+          }
+        case next_chunk:
+        case last_chunk:
+          {
+            v.append (reinterpret_cast<char*> (buffer), size);
+          }
+        }
+
+        return true;
+      }
+
+      static bool
+      param_callback (void* context,
+                      ub4* position_context,
+                      void** buffer,
+                      ub4* size,
+                      chunk_position*,
+                      void* temp_buffer,
+                      ub4 capacity);
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<std::string, id_clob>:
+      string_lob_value_traits
+    {
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<std::string, id_nclob>:
+      string_lob_value_traits
+    {
+    };
+
+    // const char* specialization for LOBs.
+    //
+    // Specialization for const char* which only supports initialization
+    // of an image from the value but not the other way around. This way
+    // we can such values to the queries.
+    //
+    class c_string_lob_value_traits
+    {
+    public:
+      typedef const char* value_type;
+      typedef const char* query_type;
+      typedef lob_callback image_type;
+
+      static void
+      set_image (param_callback_type& cb,
+                 void*& context,
+                 bool& is_null,
+                 const char* v)
+      {
+        is_null = false;
+        cb = &param_callback;
+        context = const_cast<char*> (v);
+      }
+
+      static bool
+      param_callback (void* context,
+                      ub4* position_context,
+                      void** buffer,
+                      ub4* size,
+                      chunk_position*,
+                      void* temp_buffer,
+                      ub4 capacity);
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<const char*, id_clob>:
+      c_string_lob_value_traits
+    {
+    };
+
+    template <>
+    struct LIBODB_ORACLE_EXPORT default_value_traits<const char*, id_nclob>:
+      c_string_lob_value_traits
+    {
+    };
+
+    template <std::size_t n>
+    struct default_value_traits<char[n], id_clob>:
+      c_string_lob_value_traits
+    {
+    };
+
+    template <std::size_t n>
+    struct default_value_traits<char[n], id_nclob>:
+      c_string_lob_value_traits
+    {
+    };
+
+    // std::vector<char> (buffer) specialization.
+    //
+    template <>
+    struct default_value_traits<std::vector<char>, id_blob>
+    {
+    public:
+      typedef std::vector<char> value_type;
+      typedef std::vector<char> query_type;
+      typedef lob_callback image_type;
+
+      static void
+      set_value (value_type& v,
+                 result_callback_type& cb,
+                 void*& context,
+                 bool is_null)
+      {
+        if (!is_null)
+        {
+          cb = &result_callback;
+          context = &v;
+        }
+        else
+          v.clear ();
+      }
+
+      static void
+      set_image (param_callback_type& cb,
+                 void*& context,
+                 bool& is_null,
+                 const value_type& v)
+      {
+        is_null = false;
+        cb = &param_callback;
+        context = const_cast<value_type*> (&v);
+      }
+
+      static bool
+      result_callback (void* context, void* buffer, ub4 size, chunk_position p)
+      {
+        value_type& v (*reinterpret_cast<value_type*> (context));
+
+        switch (p)
+        {
+        case one_chunk:
+        case first_chunk:
+          {
+            v.clear ();
+          }
+        case next_chunk:
+        case last_chunk:
+          {
+            char* b (reinterpret_cast<char*> (buffer));
+            v.insert (v.end (), b, b + size);
+          }
+        }
+
+        return true;
+      }
+
+      static bool
+      param_callback (void* context,
+                      ub4* position_context,
+                      void** buffer,
+                      ub4* size,
+                      chunk_position*,
+                      void* temp_buffer,
+                      ub4 capacity);
+    };
 
     //
     // type_traits