Hi!

I am trying to get the length of a VARCHAR in a UDF that receives the
VARCHAR by descriptor using Firebird 2.1.1. From other UDF source code
(e.g. fbudf.cpp) I thought the following would work:

DECLARE EXTERNAL FUNCTION MY_UDF
VARCHAR(32765) BY DESCRIPTOR
RETURNS ...etc

#include "ibase.h"

char* my_udf(PARAMDSC* par)
{
if(!par || (par->dsc_flags & DSC_null)) return NULL;

PARAMVARY* value = (PARAMVARY*) par->dsc_address;
unsigned short length = value->vary_length; // <- the varchar length

// ...
}

However, it looks as if the varchar string seems to start at address
value (i.e. par->dsc_address), not at value->vary_string (which should
be par->dsc_address+2). The following seems to work:

char* my_udf(PARAMDSC* par)
{
if(!par || (par->dsc_flags & DSC_null)) return NULL;

unsigned short length = par->dsc_length; // <- the varchar length

// ...
}

Is this how it should be? Is the struct PARAMVARY deprecated?

Cheers,
Christof