Add std::wstring support for ODBC backend

docs/api/backend.md

@@ -1,6 +1,6 @@
 # Backends reference
 
-This part of the documentation is provided for those who want towrite (and contribute!) their
+This part of the documentation is provided for those who want to write (and contribute!) their
 own backends. It is anyway recommendedthat authors of new backend see the code of some existing
 backend forhints on how things are really done.
 
@@ -28,6 +28,7 @@ enum data_type
 enum db_type
 {
     db_string,
+    db_wstring,
     db_int8,
     db_uint8,
     db_int16,
@@ -50,6 +51,7 @@ enum exchange_type
 {
     x_char,
     x_stdstring,
+    x_stdwstring,
     x_int8,
     x_uint8,
     x_int16,

docs/api/client.md

@@ -13,7 +13,7 @@ The following types are commonly used in the rest of the interface:
 
 ```cpp
 // data types, as seen by the user
-enum db_type { db_string, db_date, db_double, db_int8, db_uint8, db_int16, db_uint16, db_int32, db_uint32, db_int64, db_uint64 };
+enum db_type { db_string, db_wstring, db_date, db_double, db_int8, db_uint8, db_int16, db_uint16, db_int32, db_uint32, db_int64, db_uint64 };
 
 // deprecated data types enum which may be still used but is less precise than db_type
 enum data_type { dt_string, dt_date, dt_double, dt_integer, dt_long_long, dt_unsigned_long_long };

docs/backends/odbc.md

@@ -75,6 +75,7 @@ For the ODBC backend, this type mapping is:
 | SQL_INTEGER                                               | db_int32                   | int32_t                       |
 | SQL_BIGINT                                                | db_int64                   | int64_t                       |
 | SQL_CHAR, SQL_VARCHAR                                     | db_string                  | std::string                   |
+| SQL_WCHAR, SQL_WVARCHAR, SQL_WLONGVARCHAR                 | db_wstring                 | std::wstring                  |
 | SQL_TYPE_DATE, SQL_TYPE_TIME, SQL_TYPE_TIMESTAMP          | db_date                    | std::tm                       |
 
 Not all ODBC drivers support all datatypes.

include/private/soci-exchange-cast.h

@@ -36,6 +36,12 @@ struct exchange_type_traits<x_stdstring>
   typedef std::string value_type;
 };
 
+template <>
+struct exchange_type_traits<x_stdwstring>
+{
+  typedef std::wstring value_type;
+};
+
 template <>
 struct exchange_type_traits<x_int8>
 {

include/private/soci-vector-helpers.h

@@ -33,6 +33,8 @@ inline std::size_t get_vector_size(exchange_type e, void *data)
             return exchange_vector_type_cast<x_char>(data).size();
         case x_stdstring:
             return exchange_vector_type_cast<x_stdstring>(data).size();
+        case x_stdwstring:
+            return exchange_vector_type_cast<x_stdwstring>(data).size();
         case x_int8:
             return exchange_vector_type_cast<x_int8>(data).size();
         case x_uint8:
@@ -76,6 +78,9 @@ inline void resize_vector(exchange_type e, void *data, std::size_t newSize)
         case x_stdstring:
             exchange_vector_type_cast<x_stdstring>(data).resize(newSize);
             return;
+        case x_stdwstring:
+            exchange_vector_type_cast<x_stdwstring>(data).resize(newSize);
+            return;
         case x_int8:
             exchange_vector_type_cast<x_int8>(data).resize(newSize);
             return;
@@ -131,6 +136,7 @@ inline std::string& vector_string_value(exchange_type e, void *data, std::size_t
             return exchange_vector_type_cast<x_xmltype>(data).at(ind).value;
         case x_longstring:
             return exchange_vector_type_cast<x_longstring>(data).at(ind).value;
+        case x_stdwstring:
         case x_char:
         case x_int8:
         case x_uint8:

include/soci/exchange-traits.h

@@ -155,6 +155,13 @@ struct exchange_traits<std::string>
     enum { x_type = x_stdstring };
 };
 
+template <>
+struct exchange_traits<std::wstring>
+{
+    typedef basic_type_tag type_family;
+    enum { x_type = x_stdwstring };
+};
+
 template <>
 struct exchange_traits<std::tm>
 {

include/soci/odbc/soci-odbc.h

@@ -43,6 +43,16 @@ namespace details
     {
       return reinterpret_cast<SQLCHAR*>(const_cast<char*>(s.c_str()));
     }
+
+    inline SQLWCHAR* sqlchar_cast(std::wstring const& s)
+    {
+      return reinterpret_cast<SQLWCHAR*>(const_cast<wchar_t*>(s.c_str()));
+    }
+
+    inline SQLWCHAR* sqlchar_cast(std::u16string const& s)
+    {
+      return reinterpret_cast<SQLWCHAR*>(const_cast<char16_t*>(s.c_str()));
+    }
 }
 
 // Option allowing to specify the "driver completion" parameter of
@@ -192,6 +202,10 @@ struct odbc_standard_use_type_backend : details::standard_use_type_backend,
                           SQLSMALLINT& sqlType,
                           SQLSMALLINT& cType);
 
+    void copy_from_string(const std::wstring& s,
+                          SQLLEN& size,
+                          SQLSMALLINT& sqlType,
+                          SQLSMALLINT& cType);
 };
 
 struct odbc_vector_use_type_backend : details::vector_use_type_backend,

include/soci/ref-counted-statement.h

@@ -11,6 +11,7 @@
 #include "soci/statement.h"
 #include "soci/into-type.h"
 #include "soci/use-type.h"
+#include "soci-unicode.h"
 // std
 #include <sstream>
 

include/soci/soci-backend.h

@@ -26,6 +26,7 @@ namespace soci
 enum db_type
 {
     db_string,
+    db_wstring,
     db_int8,
     db_uint8,
     db_int16,
@@ -61,6 +62,7 @@ enum exchange_type
 {
     x_char,
     x_stdstring,
+    x_stdwstring,
     x_int8,
     x_uint8,
     x_int16,
@@ -271,6 +273,9 @@ class statement_backend
             case db_uint64: return dt_unsigned_long_long;
             case db_blob:   return dt_blob;
             case db_xml:    return dt_xml;
+
+            case db_wstring:
+                throw soci_error("unable to convert value to data_type");
         }
 
         // unreachable