From:	MERC::"uunet!WKUVX1.BITNET!MacroMan" 23-FEB-1993 04:13:59.91
To:	MACRO32@WKUVX1.BITNET
CC:	
Subj:	Here is some code for reading ODS-2 using LOGIO

Can anyone think of a reason you would want to be able to
read an ODS-2 disk by using LOGICAL IO operations or by
mounting the device /foreign?

If you do, here are the changes required to make that ODS-2 reader
for Unix recently posted work under VMS.

Changes to get the GETVMS.C ODS-2 reader for Unix
running under VMS.

e.g.

$ define disk$users dka0:
$ getvms -l [000000]
000000.DIR;1
BACKUP.SYS;1
BADBLK.SYS;1
BADLOG.SYS;1
BITMAP.SYS;1
CONTIN.SYS;1
CORIMG.SYS;1
EWS$LIBRARY.DIR;1
EWS$SERVER.DIR;1
INDEXF.SYS;1
...etc...

First change references to vms into vmsfd;

int     vmsfd = -1;

Otherwise you would have to #undefine vms

Then add a bit of code:

#ifdef VMS
/* sure this will run under VMS. It might even be the start of a useful hack */
#define index strchr
#define rindex strrchr
#include <descrip.h>
#include <ssdef.h>
#include <iodef.h>
#endif

Then modify the procedures openvms and getlb. I didn't want to bother
trying to figure out how to get the unix emulation procedures open/lseek/read
to work on a disk device mounted foreign. So it was easier to just
do the obvious QIO for reading a logical block. With the LBLK code
this will work on currently mounted filesystems too.

openvms(devname)
char    *devname;
{
        long    ifhbn;

        if ( strlen(devname) > DEVMAX )
                err1("Device name too long (%s)",devname);
#ifdef VMS
        strcpy(vmsdev,"");
#else
        strcpy(vmsdev,"/dev/");
        if ( strncmp(devname,"disk$",5) == 0 )
                devname += 5;
        if ( strncmp(devname,"vms",3) != 0 )
                strcat(vmsdev,"vms");
#endif
        strcat(vmsdev,devname);
#ifdef VMS
        {int retcode;
         struct dsc$descriptor devd;
         devd.dsc$w_length = strlen(vmsdev);
         devd.dsc$a_pointer = vmsdev;
         devd.dsc$b_class = DSC$K_CLASS_S;
         devd.dsc$b_dtype = DSC$K_DTYPE_T;
         vmsfd = 0;
         retcode = sys$assign(&devd,&vmsfd,0,0);
         if (retcode != SS$_NORMAL) vmsfd = -1;}
#else
        vmsfd=open(vmsdev,0);
#endif
        if ( vmsfd < 0 )
                err1("Can't open %s",vmsdev);

.....

}



getlb(lbn,buf)
long    lbn;
char    *buf;
{
        if ( lbn == 0L )
                err0("Bad block in file");
#ifdef VMS
        {int retcode;
         short iosb[4];
         retcode = sys$qiow(0,vmsfd,IO$_READLBLK,&iosb,0,0,
                            buf,BUFSIZ,lbn,
                            0,0,0);
         if (retcode != SS$_NORMAL) err1("QIO error %d",retcode);
         if (iosb[0] != SS$_NORMAL) err1("READLBLK error %d",iosb[0]);}
#else
        if ( lseek(vmsfd,BUFSIZE*lbn,0) == -1L ||  read(vmsfd,buf,BUFSIZE) != BU
FSIZE )
                err0("Read error");
#endif
        return(1);
}


Then hack gethdr(fnum,hp) to ignore access checks.

#ifdef VMS
        /* the user must have LOGIO priv to run this anyway. */
        return(1);
#endif

        if ( ogrp != hp->h_proj || hp->h_fpro&G_DENY )
                return(-1);
        else
                return(1);