From 35a280c5f8fa20e54bd56efd64fcdb9bd2f10dc4 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 21 Sep 2010 19:55:14 +0200
Subject: Redesign value_traits

---
 odb/mysql/query.hxx  |  42 +++++++-------
 odb/mysql/traits.cxx |  48 +++-------------
 odb/mysql/traits.hxx | 158 +++++++++++++++++++++++++--------------------------
 3 files changed, 108 insertions(+), 140 deletions(-)

diff --git a/odb/mysql/query.hxx b/odb/mysql/query.hxx
index 99d9d38..5fd89ec 100644
--- a/odb/mysql/query.hxx
+++ b/odb/mysql/query.hxx
@@ -97,14 +97,14 @@ namespace odb
       explicit
       query (val_bind<T> v)
       {
-        append<T, value_traits<T>::image_id> (v);
+        append<T, image_traits<T>::image_id> (v);
       }
 
       template <typename T>
       explicit
       query (ref_bind<T> r)
       {
-        append<T, value_traits<T>::image_id> (r);
+        append<T, image_traits<T>::image_id> (r);
       }
 
       template <image_id_type ID>
@@ -157,7 +157,7 @@ namespace odb
       query&
       operator+= (val_bind<T> v)
       {
-        append<T, value_traits<T>::image_id> (v);
+        append<T, image_traits<T>::image_id> (v);
         return *this;
       }
 
@@ -165,7 +165,7 @@ namespace odb
       query&
       operator+= (ref_bind<T> r)
       {
-        append<T, value_traits<T>::image_id> (r);
+        append<T, image_traits<T>::image_id> (r);
         return *this;
       }
 
@@ -1024,7 +1024,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, signed char>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1056,7 +1056,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, unsigned char>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1090,7 +1090,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, short>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1122,7 +1122,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, unsigned short>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1156,7 +1156,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, int>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1188,7 +1188,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, unsigned int>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1222,7 +1222,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, long long>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1254,7 +1254,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, unsigned long long>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1288,7 +1288,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, float>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1322,7 +1322,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, double>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1355,7 +1355,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, MYSQL_TIME>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1388,7 +1388,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, MYSQL_TIME>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1421,7 +1421,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, MYSQL_TIME>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1454,7 +1454,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, MYSQL_TIME>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1488,7 +1488,7 @@ namespace odb
       init (const T& v)
       {
         bool dummy;
-        value_traits<T>::set_image (image_, dummy, v);
+        value_traits<T, short>::set_image (image_, dummy, v);
       }
 
     private:
@@ -1524,7 +1524,7 @@ namespace odb
       {
         bool dummy;
         std::size_t size;
-        value_traits<T>::set_image (buffer_, size, dummy, v);
+        value_traits<T, details::buffer>::set_image (buffer_, size, dummy, v);
         size_ = static_cast<unsigned long> (size);
       }
 
@@ -1562,7 +1562,7 @@ namespace odb
       {
         bool dummy;
         std::size_t size;
-        value_traits<T>::set_image (buffer_, size, dummy, v);
+        value_traits<T, details::buffer>::set_image (buffer_, size, dummy, v);
         size_ = static_cast<unsigned long> (size);
       }
 
diff --git a/odb/mysql/traits.cxx b/odb/mysql/traits.cxx
index f90cc0b..f701978 100644
--- a/odb/mysql/traits.cxx
+++ b/odb/mysql/traits.cxx
@@ -13,29 +13,14 @@ namespace odb
 {
   namespace mysql
   {
+    using details::buffer;
+
     //
-    // value_traits<string>
+    // value_traits<string, buffer>
     //
 
-    void value_traits<string>::
-    set_image (char* s,
-               size_t c,
-               size_t& n,
-               bool& is_null,
-               const string& v)
-    {
-      is_null = false;
-      n = v.size ();
-
-      if (n > c)
-        n = c;
-
-      if (n != 0)
-        memcpy (s, v.c_str (), n);
-    }
-
-    void value_traits<string>::
-    set_image (details::buffer& b,
+    void value_traits<string, buffer>::
+    set_image (buffer& b,
                size_t& n,
                bool& is_null,
                const string& v)
@@ -51,28 +36,11 @@ namespace odb
     }
 
     //
-    // value_traits<const char*>
+    // value_traits<const char*, buffer>
     //
 
-    void value_traits<const char*>::
-    set_image (char* s,
-               size_t c,
-               size_t& n,
-               bool& is_null,
-               const char* v)
-    {
-      is_null = false;
-      n = strlen (v);
-
-      if (n > c)
-        n = c;
-
-      if (n != 0)
-        memcpy (s, v, n);
-    }
-
-    void value_traits<const char*>::
-    set_image (details::buffer& b,
+    void value_traits<const char*, buffer>::
+    set_image (buffer& b,
                size_t& n,
                bool& is_null,
                const char* v)
diff --git a/odb/mysql/traits.hxx b/odb/mysql/traits.hxx
index f05e04e..c708726 100644
--- a/odb/mysql/traits.hxx
+++ b/odb/mysql/traits.hxx
@@ -48,14 +48,14 @@ namespace odb
       id_blob
     };
 
-    template <typename T>
-    class generic_value_traits
+    template <typename T, typename I>
+    class value_traits
     {
     public:
-      typedef T type;
       typedef T value_type;
+      typedef T query_type;
+      typedef I image_type;
 
-      template <typename I>
       static void
       set_value (T& v, I i, bool is_null)
       {
@@ -65,7 +65,6 @@ namespace odb
           v = T ();
       }
 
-      template <typename I>
       static void
       set_image (I& i, bool& is_null, T v)
       {
@@ -74,163 +73,164 @@ namespace odb
       }
     };
 
+    // std::string specialization.
+    //
+    template <>
+    class LIBODB_MYSQL_EXPORT value_traits<std::string, details::buffer>
+    {
+    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&);
+    };
+
+    // 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.
+    //
+    template <>
+    class LIBODB_MYSQL_EXPORT value_traits<const char*, details::buffer>
+    {
+    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*);
+    };
+
+    //
+    // image_traits
+    //
+
     template <typename T>
-    class value_traits: public generic_value_traits<T>
+    struct default_image_id;
+
+    template <typename T>
+    class image_traits
     {
+    public:
+      static const image_id_type image_id = default_image_id<T>::image_id;
     };
 
     // Integral types.
     //
     template <>
-    class value_traits<bool>: public generic_value_traits<bool>
+    struct default_image_id<bool>
     {
-    public:
       static const image_id_type image_id = id_tiny;
     };
 
     template <>
-    class value_traits<signed char>: public generic_value_traits<signed char>
+    struct default_image_id<signed char>
     {
-    public:
       static const image_id_type image_id = id_tiny;
     };
 
     template <>
-    class value_traits<unsigned char>: public generic_value_traits<unsigned char>
+    struct default_image_id<unsigned char>
     {
-    public:
       static const image_id_type image_id = id_utiny;
     };
 
     template <>
-    class value_traits<short>: public generic_value_traits<short>
+    struct default_image_id<short>
     {
-    public:
       static const image_id_type image_id = id_short;
     };
 
     template <>
-    class value_traits<unsigned short>: public generic_value_traits<unsigned short>
+    struct default_image_id<unsigned short>
     {
-    public:
       static const image_id_type image_id = id_ushort;
     };
 
     template <>
-    class value_traits<int>: public generic_value_traits<int>
+    struct default_image_id<int>
     {
-    public:
       static const image_id_type image_id = id_long;
     };
 
     template <>
-    class value_traits<unsigned int>: public generic_value_traits<unsigned int>
+    struct default_image_id<unsigned int>
     {
-    public:
       static const image_id_type image_id = id_ulong;
     };
 
     template <>
-    class value_traits<long>: public generic_value_traits<long>
+    struct default_image_id<long>
     {
-    public:
       static const image_id_type image_id = id_longlong;
     };
 
     template <>
-    class value_traits<unsigned long>: public generic_value_traits<unsigned long>
+    struct default_image_id<unsigned long>
     {
-    public:
       static const image_id_type image_id = id_ulonglong;
     };
 
     template <>
-    class value_traits<long long>: public generic_value_traits<long long>
+    struct default_image_id<long long>
     {
-    public:
       static const image_id_type image_id = id_longlong;
     };
 
     template <>
-    class value_traits<unsigned long long>: public generic_value_traits<unsigned long long>
+    struct default_image_id<unsigned long long>
     {
-    public:
       static const image_id_type image_id = id_ulonglong;
     };
 
     // Float types.
     //
     template <>
-    class value_traits<float>: public generic_value_traits<float>
+    struct default_image_id<float>
     {
-    public:
       static const image_id_type image_id = id_float;
     };
 
     template <>
-    class value_traits<double>: public generic_value_traits<double>
+    struct default_image_id<double>
     {
-    public:
       static const image_id_type image_id = id_double;
     };
 
     // String type.
     //
     template <>
-    class LIBODB_MYSQL_EXPORT value_traits<std::string>
+    struct default_image_id<std::string>
     {
-    public:
-      typedef std::string type;
-      typedef std::string value_type;
       static const image_id_type image_id = id_string;
-
-      static void
-      set_value (std::string& v, const char* s, std::size_t n, bool is_null)
-      {
-        if (!is_null)
-          v.assign (s, n);
-        else
-          v.erase ();
-      }
-
-      static void
-      set_image (char*,
-                 std::size_t c,
-                 std::size_t& n,
-                 bool& is_null,
-                 const std::string&);
-
-      static void
-      set_image (details::buffer&,
-                 std::size_t& n,
-                 bool& is_null,
-                 const std::string&);
     };
 
-    // 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.
-    //
     template <>
-    class LIBODB_MYSQL_EXPORT value_traits<const char*>
+    struct default_image_id<const char*>
     {
-    public:
-      typedef const char* type;
-      typedef const char* value_type;
       static const image_id_type image_id = id_string;
-
-      static void
-      set_image (char*,
-                 std::size_t c,
-                 std::size_t& n,
-                 bool& is_null,
-                 const char*);
-
-      static void
-      set_image (details::buffer&,
-                 std::size_t& n,
-                 bool& is_null,
-                 const char*);
     };
   }
 }
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