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/* $Id: backpage.c,v 3.0 1991/09/09 20:18:23 davison Trn $
*/
/* This software is Copyright 1991 by Stan Barber.
*
* Permission is hereby granted to copy, reproduce, redistribute or otherwise
* use this software as long as: there is no monetary profit gained
* specifically from the use or reproduction of this software, it is not
* sold, rented, traded or otherwise marketed, and this copyright notice is
* included prominently in any copy made.
*
* The authors make no claims as to the fitness or correctness of this software
* for any use whatsoever, and it is provided as is. Any use of this software
* is at the user's own risk.
*/
#include "EXTERN.h"
#include "common.h"
#include "intrp.h"
#include "final.h"
#include "INTERN.h"
#include "backpage.h"
ART_LINE maxindx = -1;
void
backpage_init()
{
char *varyname;
varyname = filexp(VARYNAME);
close(creat(varyname,0600));
varyfd = open(varyname,2);
UNLINK(varyname);
if (varyfd < 0) {
printf(cantopen,varyname) FLUSH;
sig_catcher(0);
}
}
/* virtual array read */
ART_POS
vrdary(indx)
ART_LINE indx;
{
int subindx;
long offset;
#ifdef DEBUG
if (indx > maxindx) {
printf("vrdary(%ld) > %ld\n",(long)indx, (long)maxindx) FLUSH;
return 0;
}
#endif
if (indx < 0)
return 0;
subindx = indx % VARYSIZE;
offset = (indx - subindx) * sizeof(varybuf[0]);
if (offset != oldoffset) {
if (oldoffset >= 0) {
#ifndef lint
(void)lseek(varyfd,oldoffset,0);
write(varyfd, (char *)varybuf,sizeof(varybuf));
#endif /* lint */
}
#ifndef lint
(void)lseek(varyfd,offset,0);
read(varyfd,(char *)varybuf,sizeof(varybuf));
#endif /* lint */
oldoffset = offset;
}
return varybuf[subindx];
}
/* write to virtual array */
void
vwtary(indx,newvalue)
ART_LINE indx;
ART_POS newvalue;
{
int subindx;
long offset;
#ifdef DEBUG
if (indx < 0)
printf("vwtary(%ld)\n",(long)indx) FLUSH;
if (!indx)
maxindx = 0;
if (indx > maxindx) {
if (indx != maxindx + 1)
printf("indx skipped %d-%d\n",maxindx+1,indx-1) FLUSH;
maxindx = indx;
}
#endif
subindx = indx % VARYSIZE;
offset = (indx - subindx) * sizeof(varybuf[0]);
if (offset != oldoffset) {
if (oldoffset >= 0) {
#ifndef lint
(void)lseek(varyfd,oldoffset,0);
write(varyfd,(char *)varybuf,sizeof(varybuf));
#endif /* lint */
}
#ifndef lint
(void)lseek(varyfd,offset,0);
read(varyfd,(char *)varybuf,sizeof(varybuf));
#endif /* lint */
oldoffset = offset;
}
varybuf[subindx] = newvalue;
}
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