Add very simple XML and CLOB support to ODBC backend

Handle them as plain strings and rely on the ODBC driver to perform the
required conversions.

docs/lobs.md

@@ -54,3 +54,10 @@ For PostgreSQL, these types are:
 
 For Firebird, there is no special XML support, but `BLOB SUB_TYPE TEXT` can be
 used for storing it, as well as long strings.
+
+For ODBC backend, these types depend on the type of the database connected to.
+In particularly important special case of Microsoft SQL Server, these types
+are:
+
+* `xml`
+* `text`

src/backends/odbc/standard-into-type.cpp

@@ -33,6 +33,8 @@ void odbc_standard_into_type_backend::define_by_pos(
         data = buf_;
         break;
     case x_stdstring:
+    case x_longstring:
+    case x_xmltype:
         odbcType_ = SQL_C_CHAR;
         // Patch: set to min between column size and 100MB (used ot be 32769)
         // Column size for text data type can be too large for buffer allocation
@@ -159,6 +161,14 @@ void odbc_standard_into_type_backend::post_fetch(
                 throw soci_error("Buffer size overflow; maybe got too large string");
             }
         }
+        else if (type_ == x_longstring)
+        {
+            exchange_type_cast<x_longstring>(data_).value = buf_;
+        }
+        else if (type_ == x_xmltype)
+        {
+            exchange_type_cast<x_xmltype>(data_).value = buf_;
+        }
         else if (type_ == x_stdtm)
         {
             std::tm& t = exchange_type_cast<x_stdtm>(data_);

src/backends/odbc/standard-use-type.cpp

@@ -113,6 +113,15 @@ void* odbc_standard_use_type_backend::prepare_for_bind(
     }
     break;
 
+    case x_longstring:
+        copy_from_string(exchange_type_cast<x_longstring>(data_).value,
+                         size, sqlType, cType);
+        break;
+    case x_xmltype:
+        copy_from_string(exchange_type_cast<x_xmltype>(data_).value,
+                         size, sqlType, cType);
+        break;
+
     // unsupported types
     default:
         throw soci_error("Use element used with non-supported type.");

tests/odbc/test-odbc-mssql.cpp

@@ -116,6 +116,24 @@ struct table_creator_for_get_affected_rows : table_creator_base
     }
 };
 
+struct table_creator_for_clob : table_creator_base
+{
+    table_creator_for_clob(soci::session & sql)
+        : table_creator_base(sql)
+    {
+        sql << "create table soci_test(id integer, s text)";
+    }
+};
+
+struct table_creator_for_xml : table_creator_base
+{
+    table_creator_for_xml(soci::session & sql)
+        : table_creator_base(sql)
+    {
+        sql << "create table soci_test(id integer, x xml)";
+    }
+};
+
 //
 // Support for SOCI Common Tests
 //
@@ -147,6 +165,16 @@ class test_context : public test_context_base
         return new table_creator_for_get_affected_rows(s);
     }
 
+    tests::table_creator_base* table_creator_clob(soci::session& s) const
+    {
+        return new table_creator_for_clob(s);
+    }
+
+    tests::table_creator_base* table_creator_xml(soci::session& s) const
+    {
+        return new table_creator_for_xml(s);
+    }
+
     std::string to_date_time(std::string const &datdt_string) const
     {
         return "convert(datetime, \'" + datdt_string + "\', 120)";