From: hoffman@xdelta.zko.dec.nospam
Sent: Thursday, October 12, 2000 9:59 AM
To: Info-VAX@Mvb.Saic.Com
Subject: Re: Reading and writing files via $QIO in C


In article <5.0.0.25.0.20001011144441.01bc82e0@24.8.96.48>, Dan Sugalski <dan@sidhe.org> writes:
:Well, I'm about to embark on yet another Adventure In C. (Lucky me...) This 
:time I need to either open and rip through an existing file, or create and 
:dump data to a new file.

  Do you need to use $qio (readvblk-level file access), or will direct RMS 
  access from C work?  Or do you need memory-mapped access to the file?
  (I usually prefer direct RMS access, but I will drop down to use virtual
  $qio operations when I need speed -- though only when I do not need the 
  cluster-aware caching and interlocking provided by RMS.)

:Anyone got example code kicking around that I can peer at for a bit that 
:does this sort of thing?

  Ayup...  Here are a few different approaches:

    www.openvms.compaq.com/freeware/srh_examples/RMS_EXAMPLES.C
    www.openvms.compaq.com/wizard/wiz_2486.html
    attached (old, crufty) example...

  Probably a few others kicking around...

 --------------------------- pure personal opinion ---------------------------
   Hoff (Stephen) Hoffman   OpenVMS Engineering   hoffman#xdelta.zko.dec.com



#module	EXAMPLE "SRH X1.0-000"
#pragma builtins

/*
** COPYRIGHT (c) 1992 BY
** DIGITAL EQUIPMENT CORPORATION, MAYNARD, MASSACHUSETTS.
** ALL RIGHTS RESERVED.
**
** THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY BE USED AND COPIED
** ONLY  IN  ACCORDANCE  OF  THE  TERMS  OF  SUCH  LICENSE  AND WITH THE
** INCLUSION OF THE ABOVE COPYRIGHT NOTICE. THIS SOFTWARE OR  ANY  OTHER
** COPIES THEREOF MAY NOT BE PROVIDED OR OTHERWISE MADE AVAILABLE TO ANY
** OTHER PERSON.  NO TITLE TO AND  OWNERSHIP OF THE  SOFTWARE IS  HEREBY
** TRANSFERRED.
**
** THE INFORMATION IN THIS SOFTWARE IS  SUBJECT TO CHANGE WITHOUT NOTICE
** AND  SHOULD  NOT  BE  CONSTRUED  AS A COMMITMENT BY DIGITAL EQUIPMENT
** CORPORATION.
**
** DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE  OR  RELIABILITY OF ITS
** SOFTWARE ON EQUIPMENT WHICH IS NOT SUPPLIED BY DIGITAL.
*/

/*
**++
**  Facility:
**
**	Examples
**
**  Version: V1.0
**
**  Abstract:
**
**	Shows some RMS operations from C
**
**  Author:
**	Unknown
**
**  Creation Date:  1-Jan-1990
**
**  Modification History:
**--
*/
#include <stdio.h>
#include <iodef.h>
#include <strdef.h>
#include <fibdef.h>
#include <ssdef.h>
#include <libdef.h>
#include <stat.h>
#include <file.h>
#include <descrip.h>

typedef struct {
  short int iosb1;
  long int  length;
  short int spec;
} iosb;

typedef struct {
  long int fiblength;
  long int fibaddress;
} fibd;

typedef struct {
  short int atr_size;
  short int atr_type;
  long int  atr_address;
} acb;

static fibd             fibdescr;
static iosb             iostat;
static short int        disk_chan;
static stat_t           sbuff;
static struct fibdef    *fib;
static char             data[512];

#define BAD(x) (!((x) & 1))

main (int argc, char *argv[])

{
  int i,j,k;
  $DESCRIPTOR(device, "work3:");
  $DESCRIPTOR(filename, "temp.dat");
  int status;

  status = sys$assign (&device, &disk_chan, NULL, NULL);
  if (BAD(status)) lib$stop (status);
  printf ("chanel = %d\n", disk_chan);

  if (access("temp.dat",0)) {

/*
 * This crashes and burns

    fibdescr.fiblength  = sizeof (struct fibdef);
    fibdescr.fibaddress = fib;

    fib->fib$r_exctl_overlay.fib$r_exctl_bits.fib$v_extend     = 1;
    fib->fib$r_exctl_overlay.fib$r_exctl_bits.fib$v_aldef      = 1;
    fib->fib$l_exsz                                            = 5;
    fib->fib$l_exvbn                                           = 0;
    status = sys$qiow (NULL, disk_chan, (IO$_CREATE | IO$M_EXTEND), &iostat, 
                       NULL, NULL, 
                       &fibdescr, NULL, NULL, NULL, NULL, NULL);
    printf ("alloc = %d\n", fib->fib$l_exsz);
    printf ("vbn = %d\n", fib->fib$l_exvbn);
    printf ("status = %x, %d : %d\n", status, status, iostat.length);
    printf ("iostatus = %x, %d : %d\n", iostat.iosb1, iostat.iosb1);
*/

/* */
  j = open ("temp.dat", O_WRONLY | O_CREAT | O_TRUNC);
  for (i = 0; i < 512; i++) data[i] = i;
  write (j, data, 512);
  close (j);
/* */
  }


  stat ("temp.dat", &sbuff);
  printf ("fid = (%d %d %d)\n",sbuff.st_ino[0],sbuff.st_ino[1],sbuff.st_ino[2]);

  fib = (struct fibdef *) calloc (sizeof(struct fibdef), 1);
  fib->fib$r_acctl_overlay.fib$r_acctl_bits0.fib$v_nowrite = 1;
  fib->fib$r_acctl_overlay.fib$r_acctl_bits0.fib$v_write   = 1;
  fib->fib$r_acctl_overlay.fib$r_acctl_fields2.fib$b_wsize = 7;
  fib->fib$r_fid_overlay.fib$w_fid[0]                      = sbuff.st_ino[0];
  fib->fib$r_fid_overlay.fib$w_fid[1]                      = sbuff.st_ino[1];
  fib->fib$r_fid_overlay.fib$w_fid[2]                      = sbuff.st_ino[2];

  fibdescr.fiblength  = FIB$K_LENGTH;
  fibdescr.fibaddress = &(fib->fib$r_acctl_overlay.fib$l_acctl);

  status = sys$qiow (NULL, disk_chan, (IO$_ACCESS | IO$M_ACCESS),
                     &iostat, NULL, NULL, 
                     &fibdescr, NULL, NULL, NULL, NULL, NULL);
  if (BAD(status)) lib$stop (status);
  if (BAD(iostat.iosb1)) lib$stop (iostat.iosb1);

  fib->fib$r_acctl_overlay.fib$l_acctl = 0;
  fibdescr.fiblength  = sizeof (struct fibdef);
  fibdescr.fibaddress = fib;

  fib->fib$r_exctl_overlay.fib$r_exctl_bits.fib$v_extend     = 1;
  fib->fib$r_exctl_overlay.fib$r_exctl_bits.fib$v_aldef      = 1;
  fib->fib$l_exsz                                            = 5;
  fib->fib$l_exvbn                                           = 0;
  status = sys$qiow (NULL, disk_chan, (IO$_MODIFY), &iostat, 
                     NULL, NULL, 
                     &fibdescr, NULL, NULL, NULL, NULL, NULL);
  printf ("alloc = %d\n", fib->fib$l_exsz);
  printf ("vbn = %d\n", fib->fib$l_exvbn);
  printf ("status = %x, %d : %d\n", status, status, iostat.length);
  printf ("iostatus = %x, %d : %d\n", iostat.iosb1, iostat.iosb1);

  fib->fib$r_exctl_overlay.fib$w_exctl = 0;

  for (j = 1; j < 5; j++) {
    for (i = 0; i < 512; i++) data[i] = j;
    status = sys$qiow (NULL, disk_chan, (IO$_WRITEVBLK), &iostat, NULL, NULL,
                       data, 512, j, NULL, NULL, NULL);
    printf ("write status = %x, %d : %d\n", status, status, iostat.length);
  }

  for (j = 1; j < 5; j++) {
    for (i = 0; i < 512; i++) data[i] = 0;
    status = sys$qiow (NULL, disk_chan, (IO$_READVBLK), &iostat, NULL, NULL,
                       data, 512, j, NULL, NULL, NULL);
    printf ("read status = %x, %d : %d\n", status, status, iostat.length);
    printf ("data[0] = %d\n", (long) data[0]);
  }

  status = sys$qiow (NULL, disk_chan, (IO$_DEACCESS),
                     &iostat, NULL, NULL, 
                     &fibdescr, NULL, NULL, NULL, NULL, NULL);
  if (BAD(status)) lib$stop (status);

  exit(1);
}