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telldir.c revision 1.13
      1  1.13   thorpej /*	$NetBSD: telldir.c,v 1.13 2001/12/30 19:27:42 thorpej Exp $	*/
      2   1.4       cgd 
      3   1.1       cgd /*
      4   1.2       jtc  * Copyright (c) 1983, 1993
      5   1.2       jtc  *	The Regents of the University of California.  All rights reserved.
      6   1.1       cgd  *
      7   1.1       cgd  * Redistribution and use in source and binary forms, with or without
      8   1.1       cgd  * modification, are permitted provided that the following conditions
      9   1.1       cgd  * are met:
     10   1.1       cgd  * 1. Redistributions of source code must retain the above copyright
     11   1.1       cgd  *    notice, this list of conditions and the following disclaimer.
     12   1.1       cgd  * 2. Redistributions in binary form must reproduce the above copyright
     13   1.1       cgd  *    notice, this list of conditions and the following disclaimer in the
     14   1.1       cgd  *    documentation and/or other materials provided with the distribution.
     15   1.1       cgd  * 3. All advertising materials mentioning features or use of this software
     16   1.1       cgd  *    must display the following acknowledgement:
     17   1.1       cgd  *	This product includes software developed by the University of
     18   1.1       cgd  *	California, Berkeley and its contributors.
     19   1.1       cgd  * 4. Neither the name of the University nor the names of its contributors
     20   1.1       cgd  *    may be used to endorse or promote products derived from this software
     21   1.1       cgd  *    without specific prior written permission.
     22   1.1       cgd  *
     23   1.1       cgd  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24   1.1       cgd  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25   1.1       cgd  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26   1.1       cgd  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27   1.1       cgd  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28   1.1       cgd  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29   1.1       cgd  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30   1.1       cgd  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31   1.1       cgd  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32   1.1       cgd  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33   1.1       cgd  * SUCH DAMAGE.
     34   1.1       cgd  */
     35   1.1       cgd 
     36   1.5  christos #include <sys/cdefs.h>
     37   1.1       cgd #if defined(LIBC_SCCS) && !defined(lint)
     38   1.4       cgd #if 0
     39   1.4       cgd static char sccsid[] = "@(#)telldir.c	8.1 (Berkeley) 6/4/93";
     40   1.4       cgd #else
     41  1.13   thorpej __RCSID("$NetBSD: telldir.c,v 1.13 2001/12/30 19:27:42 thorpej Exp $");
     42   1.4       cgd #endif
     43   1.1       cgd #endif /* LIBC_SCCS and not lint */
     44   1.1       cgd 
     45   1.6       jtc #include "namespace.h"
     46   1.1       cgd #include <sys/param.h>
     47  1.10     lukem 
     48  1.10     lukem #include <assert.h>
     49   1.1       cgd #include <dirent.h>
     50   1.1       cgd #include <stdlib.h>
     51   1.1       cgd #include <unistd.h>
     52   1.6       jtc 
     53   1.6       jtc #ifdef __weak_alias
     54  1.12   mycroft __weak_alias(telldir,_telldir)
     55   1.6       jtc #endif
     56   1.1       cgd 
     57   1.1       cgd /*
     58   1.1       cgd  * The option SINGLEUSE may be defined to say that a telldir
     59   1.1       cgd  * cookie may be used only once before it is freed. This option
     60   1.1       cgd  * is used to avoid having memory usage grow without bound.
     61   1.1       cgd  */
     62   1.1       cgd #define SINGLEUSE
     63   1.1       cgd 
     64   1.1       cgd /*
     65   1.1       cgd  * One of these structures is malloced to describe the current directory
     66   1.1       cgd  * position each time telldir is called. It records the current magic
     67   1.1       cgd  * cookie returned by getdirentries and the offset within the buffer
     68   1.1       cgd  * associated with that return value.
     69   1.1       cgd  */
     70   1.1       cgd struct ddloc {
     71   1.1       cgd 	struct	ddloc *loc_next;/* next structure in list */
     72   1.1       cgd 	long	loc_index;	/* key associated with structure */
     73   1.8     perry 	off_t	loc_seek;	/* magic cookie returned by getdirentries */
     74   1.1       cgd 	long	loc_loc;	/* offset of entry in buffer */
     75   1.1       cgd };
     76   1.1       cgd 
     77   1.1       cgd #define	NDIRHASH	32	/* Num of hash lists, must be a power of 2 */
     78   1.8     perry #define	LOCHASH(i)	(((int)i)&(NDIRHASH-1))
     79   1.1       cgd 
     80   1.1       cgd static long	dd_loccnt;	/* Index of entry for sequential readdir's */
     81   1.1       cgd static struct	ddloc *dd_hash[NDIRHASH];   /* Hash list heads for ddlocs */
     82   1.1       cgd 
     83   1.1       cgd /*
     84   1.1       cgd  * return a pointer into a directory
     85   1.1       cgd  */
     86   1.1       cgd long
     87   1.1       cgd telldir(dirp)
     88   1.1       cgd 	const DIR *dirp;
     89   1.1       cgd {
     90  1.13   thorpej 	long idx;
     91   1.7     perry 	struct ddloc *lp;
     92   1.1       cgd 
     93  1.10     lukem 
     94   1.1       cgd 	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
     95   1.1       cgd 		return (-1);
     96  1.13   thorpej 	idx = dd_loccnt++;
     97  1.13   thorpej 	lp->loc_index = idx;
     98   1.1       cgd 	lp->loc_seek = dirp->dd_seek;
     99   1.1       cgd 	lp->loc_loc = dirp->dd_loc;
    100  1.13   thorpej 	lp->loc_next = dd_hash[LOCHASH(idx)];
    101  1.13   thorpej 	dd_hash[LOCHASH(idx)] = lp;
    102  1.13   thorpej 	return (idx);
    103   1.1       cgd }
    104   1.1       cgd 
    105   1.1       cgd /*
    106   1.1       cgd  * seek to an entry in a directory.
    107   1.1       cgd  * Only values returned by "telldir" should be passed to seekdir.
    108   1.1       cgd  */
    109   1.1       cgd void
    110   1.2       jtc __seekdir(dirp, loc)
    111   1.7     perry 	DIR *dirp;
    112   1.1       cgd 	long loc;
    113   1.1       cgd {
    114   1.7     perry 	struct ddloc *lp;
    115   1.7     perry 	struct ddloc **prevlp;
    116   1.1       cgd 	struct dirent *dp;
    117  1.10     lukem 
    118  1.10     lukem 	_DIAGASSERT(dirp != NULL);
    119   1.1       cgd 
    120   1.1       cgd 	prevlp = &dd_hash[LOCHASH(loc)];
    121   1.1       cgd 	lp = *prevlp;
    122   1.1       cgd 	while (lp != NULL) {
    123   1.1       cgd 		if (lp->loc_index == loc)
    124   1.1       cgd 			break;
    125   1.1       cgd 		prevlp = &lp->loc_next;
    126   1.1       cgd 		lp = lp->loc_next;
    127   1.1       cgd 	}
    128   1.1       cgd 	if (lp == NULL)
    129   1.1       cgd 		return;
    130   1.1       cgd 	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
    131   1.1       cgd 		goto found;
    132   1.2       jtc 	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
    133   1.1       cgd 	dirp->dd_seek = lp->loc_seek;
    134   1.1       cgd 	dirp->dd_loc = 0;
    135   1.1       cgd 	while (dirp->dd_loc < lp->loc_loc) {
    136   1.1       cgd 		dp = readdir(dirp);
    137   1.1       cgd 		if (dp == NULL)
    138   1.1       cgd 			break;
    139   1.1       cgd 	}
    140   1.1       cgd found:
    141   1.1       cgd #ifdef SINGLEUSE
    142   1.1       cgd 	*prevlp = lp->loc_next;
    143   1.9     enami 	free(lp);
    144   1.1       cgd #endif
    145   1.1       cgd }
    146