BSD 4_3 development

[unix-history] / usr / contrib / rn / backpage.c

/* $Header: backpage.c,v 4.3 85/05/01 11:36:03 lwall Exp $
*
* $Log:        backpage.c,v $
* Revision 4.3  85/05/01  11:36:03  lwall
* Baseline for release with 4.3bsd.
* 
*/

#include "EXTERN.h"
#include "common.h"
#include "intrp.h"
#include "final.h"
#include "INTERN.h"
#include "backpage.h"

ART_LINE maxindx = -1;
long lseek();

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 DEBUGGING
   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 DEBUGGING
   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;
}