added depend label

[unix-history] / usr / src / usr.bin / ex / ex_tagio.c

/* Copyright (c) 1985 Regents of the University of California */

/*
* These routines are for faster tag lookup.  They support the binary
* search used in tagfind() instead of the linear search.  The speedup
* is quite noticable looking for a tag at the end of a long tags
* file.  Define FASTTAG in the Makefile to use these routines.
*/

#ifdef FASTTAG
#ifndef lint
static char *sccsid = "@(#)ex_tagio.c   7.4 (Berkeley) %G%";
#endif

#ifndef vms
#include <sys/file.h>
#else
#include <file.h>
#endif
#include "ex.h"

static long offset = -1;
static long block = -1;
static int bcnt = 0;
static int b_size = MAXBSIZE;
static char *ibuf;

topen(file, buf)
char *file, *buf;
{
       int fd;
       struct stat statb;

       offset = -1;
       block = -1;
       if ((fd = open(file, O_RDONLY, 0)) < 0)
               return(-1);
       if (fstat(fd, &statb) < 0) {
               (void)close(fd);
               return(-1);
       }
       ibuf = buf;
       b_size = statb.st_blksize;
       return(fd);
}

tseek(fd, off)
int fd;
long off;
{
       int nblock;

       nblock = off / b_size * b_size;
       offset = off % b_size;
       if (nblock == block)
               return(0);
       block = nblock;
       if (lseek(fd, nblock, L_SET) < 0)
               return(-1);
       if ((bcnt = read(fd, ibuf, b_size)) < 0)
               return(-1);
       return(0);
}

tgets(buf, cnt, fd)
register char *buf;
int cnt;
int fd;
{
       register char *cp;
       register cc;

       cc = offset;
       if (cc == -1) {
               if ((bcnt = read(fd, ibuf, b_size)) <= 0)
                       return (NULL);
               cc = 0;
               block = 0;
       }
       if (bcnt == 0)          /* EOF */
               return(NULL);
       cp = ibuf + cc;
       while (--cnt > 0) {
               if (++cc > bcnt) {
                       block += b_size;
                       if ((bcnt = read(fd, ibuf, b_size)) <= 0) {
                               offset = cc;
                               return (NULL);
                       }
                       cp = ibuf;
                       cc = 1;
               }
               if ((*buf++ = *cp++) == '\n')
                       break;
       }
       *--buf = NULL;
       offset = cc;
       return(1);
}

tclose(fd)
int fd;
{
       (void)close(fd);
       offset = -1;
       block = -1;
       bcnt = 0;
}
#endif