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/* 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
#if     !defined(lint) && defined(DOSCCS)
static char *sccsid = "@(#)ex_tagio.c   7.3 (Berkeley) 1/31/86";
#endif

#include <fcntl.h>
#include <stdio.h>

#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;*/
        bsize = MAXBSIZE;
        return(fd);
}

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

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

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