SQLBindParameter to prepare for SQLPutData using C++ and SQL Native Client

I'm trying to use SQLBindParameter to prepare my driver for input via SQLPutData. The field in the database is a TEXT field. My function is crafted based on MS's example here: http://msdn.microsoft.com/en-us/library/ms713824(VS.85).aspx.

I've setup the environment, made the connection, and prepared my statement successfully but when I call SQLBindParam (using code below) it consistently fails reporting: [Microsoft][SQL Native Client]Invalid precision value

int col_num = 1;
SQLINTEGER length = very_long_string.length( );
retcode = SQLBindParameter( StatementHandle,
            col_num,
            SQL_PARAM_INPUT,
            SQL_C_BINARY,
            SQL_LONGVARBINARY,
            NULL,
            NULL,            
            (SQLPOINTER) col_num,     
            NULL,                 
            &length );

The above relies on the driver in use returning "N" for the SQL_NEED_LONG_DATA_LEN information type in SQLGetInfo. My driver returns "Y". How do I bind so that I can use SQLPutData?

From stackoverflow antik

• you're passing NULL as the buffer length, this is an in/out param that shoudl be the size of the col_num parameter. Also, you should pass a value for the ColumnSize or DecimalDigits parameters.

  http://msdn.microsoft.com/en-us/library/ms710963(VS.85).aspx

  From gbjbaanb

• Though it doesn't look just like the documentation's example code, I found the following solution to work for what I'm trying to accomplish. Thanks gbjbaanb for making me retest my input combinations to SQLBindParameter.

      SQLINTEGER length;
      RETCODE retcode = SQLBindParameter( StatementHandle,
          col_num,      // position of the parameter in the query
          SQL_PARAM_INPUT,
          SQL_C_CHAR,
          SQL_VARCHAR,
          data_length,        // size of our data
          NULL,               // decimal precision: not used our data types
          &my_string,         // SQLParamData will return this value later to indicate what data it's looking for so let's pass in the address of our std::string
          data_length,
          &length );          // it needs a length buffer
  
      // length in the following operation must still exist when SQLExecDirect or SQLExecute is called
      // in my code, I used a pointer on the heap for this.
      length = SQL_LEN_DATA_AT_EXEC( data_length );
  

  After a statement is executed, you can use SQLParamData to determine what data SQL wants you to send it as follows:

      std::string* my_string;
      // set string pointer to value given to SQLBindParameter
      retcode = SQLParamData( StatementHandle, (SQLPOINTER*) &my_string );
  

  Finally, use SQLPutData to send the contents of your string to SQL:

      // send data in chunks until everything is sent
      SQLINTEGER len;
      for ( int i(0); i < my_string->length( ); i += CHUNK_SIZE )
      {
          std::string substr = my_string->substr( i, CHUNK_SIZE );
  
          len = substr.length( );
  
          retcode = SQLPutData( StatementHandle, (SQLPOINTER) substr.c_str( ), len );
      }
  

  From antik