Re: Looking for good article on using the C runtime record I/O functions (_Rread, _Ropen, ect)

Charles

I've often thought of using the _R* C functions to update Julian Monypenny's generic file I/O stuff - he used an internally-defined file - and those can't deal with NULL (for sure) and varying length (maybe).

The C functions give us even more of the I/O capabilities than RPG does - and you can work directly with the buffers.

For most things, there probably isn't a good-enough reason to use C functions instead of native RPG, but this one is, IMO.

Now to find some time!!

Vern

On 6/27/2014 7:19 AM, Charles Wilt wrote:

Thanks Thomas,

I ended up not using the C I/O for other reasons..

Charles


On Fri, Jun 27, 2014 at 2:27 AM, <thomas.raddatz@xxxxxx> wrote:

Charles,

I use the "ILE C/C++ Runtime Library Functions" PDF to get the information
I need about the C record IO functions.

Basically the "_Ropen" functions return a _RFILE structure, which has
pointer to the IO buffer as well as the NULL indicator map:

Information for controlling opened record I/O operations:

typedef _Packed struct {
char reserved1[16];
volatile void *const *const in_buf;
volatile void *const *const out_buf;
char reserved2[48];
_RIOFB_T riofb;
char reserved3[32];
const unsigned int buf_length;
char reserved4[28];
volatile char *const in_null_map;
volatile char *const out_null_map;
volatile char *const null_key_map;
char reserved5[48];
const int min_length;
short null_map_len;
short null_key_map_len;
char reserved6[8];
}_RFILE;


The NULL map buffers are always present, regardless of the file has null
capable fields or not. The sequence number of a field (starting at 1 for
RPG) can be used to get its NULL indicator from the NULL map. You can
check the NULL status of a given field by comparing its NULL indicator
with 1 (= NULL) or 0 (= not NULL). A field is set to NULL by setting its
NULL indicator to 1.

I wrapped the C functions with RPG and use it as shown here:

// Read a record
isEOF = CIO_read(hFile02: bFalse: IO_Buff: IO_NullMap)

// Check field for NULL
if (IO_NullMap(FLDL0100.F1SEQ) = 1);
// field is NULL
else;
// field is not NULL
endif;

// Set field to NULL
IO_NullMap(F1SEQ) = 1


Regards,

Thomas.


rpg400-l-bounces@xxxxxxxxxxxx schrieb am 24.06.2014 23:17:53:

Von: charles.wilt@xxxxxxxxx
An: rpg400-l@xxxxxxxxxxxx,
Datum: 24.06.2014 23:18
Betreff: Re: Looking for good article on using the C runtime record
I/O functions (_Rread, _Ropen, ect)
Gesendet von: rpg400-l-bounces@xxxxxxxxxxxx

In particular, I'm curious how NULL fields are handled when using the C
functions from RPG.

Charles


On Tue, Jun 24, 2014 at 5:02 PM, Charles Wilt <charles.wilt@xxxxxxxxx>
wrote:

I need a refresher...

Thanks!
Charles

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