Scratchpads on 32-bit and 64-bit operating systems

To make your UDF or method code portable between 32-bit and 64-bit operating systems, you must be cautious when you create and use scratchpads that contain 64-bit values.

It is recommended that you do not declare an explicit length variable for a scratchpad structure that contains one or more 64-bit values, such as 64-bit pointers or sqlint64 BIGINT variables.

Following is a sample structure declaration for a scratchpad:

   struct sql_scratchpad
   {
      sqlint32 length;
      char data[100];
   };

When defining its own structure for the scratchpad, a routine has two choices:

Redefine the entire scratchpad sql_scratchpad, in which case it needs to include an explicit length field. For example:

   struct sql_spad
   {
     sqlint32 length;
     sqlint32 int_var;
     sqlint64 bigint_var;
   };
   void SQL_API_FN routine( ..., struct sql_spad* scratchpad, ... )
   {
     /* Use scratchpad */
   }

Redefine just the data portion of the scratchpad sql_scratchpad, in which case no length field is needed.

   struct spaddata
   {
     sqlint32 int_var;
     sqlint64 bigint_var;
   };
   void SQL_API_FN routine( ..., struct sql_scratchpad* spad, ... )
   {
     struct spaddata* scratchpad = (struct spaddata*)spad→data;
     /* Use scratchpad */
   }

As the application cannot change the value in the length field of the scratchpad, there is no significant benefit to coding the routine as shown in the first example. The second example is also portable between computers with different word sizes, so it is the preferred way of writing the routine.