FreeTDS Development Group

["Thompson, Bill D (London)" <ThompBil AT exchange.uk.ml.com>]

Freddy, 

here's a lttle .txt document I'm working with, which describes the relvant
aspects of dblib dbconvert() and ctlib cs_convert()

As far as dbconvert goes, I (hope I) implemented the destlen functionality
in tds_convert_any().
As you may be aware though, not all the tds_convert_x functions in convert.c
use the tds_convert_any function.
This includes tds_convert_text(), hence (in my view) some of the problems
that have occurred - the handling of return data should be in one place
only!

 <<destlen.txt>> 
Bill 



dbconvert precis (Sybase)
-------------------------

destlen - The length, in bytes, of the destination variable. 
          destlen is ignored for fixed-length datatypes. 
          For a SYBCHAR, SYBBOUNDARY or SYBSENSITIVITY destination, 
          the value of destlen must be the total length of the destination 
buffer space. 

The following table describes special values for destlen:

Special values for destlen (dbconvert) 

destlen  Applicable To                  Meaning

-1       SYBCHAR, SYBBOUNDARY,          There is sufficient space available. 
         SYBSENSITIVITY                 The string will be trimmed of 
trailing blanks 
                                        and given a terminating null.
 
-2       SYBCHAR                        There is sufficient space available. 
                                        The string will not be trimmed of 
trailing blanks, 
                                        but will be given a terminating null.

Notes: SYBBOUNDARY and SYBSENSITIVITY destinations are always null-terminated.

dbconvert precis (Microsoft)
----------------------------
destlen - The length, in bytes, of the destination variable. 
          This length is used for the following desttype data type tokens: 

          SQLCHAR, SQLVARCHAR, SQLTEXT
          SQLBINARY, SQLVARBINARY, SQLIMAGE
          SQLINTN, SQLFLTN, SQLMONEYN, SQLDATETIMN 
          
          The destlen is ignored for all fixed-length, non-NULL data types. 

          When dest points to a DBCHAR string or a DBBINARY array, 
          the value of destlen must be the total length of the destination 
buffer space, 
          or -1 to indicate that there is sufficient space available. 
          Note that when dest points to a DBCHAR string, 
          a destlen of -1 causes the character string to be given a 
terminating null. 



cs_convert precis
-----------------

destfmt - A pointer to a CS_DATAFMT structure describing the destination data 
format. 
          The following table lists the fields in *destfmt that are used.

Field Name      Set It To
----------      ---------
 
datatype        A type constant representing the desired destination datatype 
                (CS_CHAR_TYPE, CS_BINARY_TYPE, and so on).
 
maxlength       The length of the destdata buffer.
 
locale          A pointer to a CS_LOCALE structure containing localization 
values for the destination data, or NULL to use localization values from 
*context.
 
format          A bit mask of the following symbols:

                For character and text destinations only, 
                use CS_FMT_NULLTERM to null-terminate the data, 
                or CS_FMT_PADBLANK to pad to the full length of the variable 
with spaces. 
                For character, binary, text, and image destinations, 
                use CS_FMT_PADNULL to pad to the full length of the variable 
with nulls.
                When converting from a character source to a character 
destination, 
                For any type of destination, use CS_FMT_UNUSED if no format 
information is being provided.

my notes:       obviously FMT_PADBLANK and FMT_PADNULL should be mutually 
exclusive, although their
                implementaion as bitmaps means it is possible to specify 
both(!)