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	1	/*
	2	* Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
	11	*
	12	* This Original Code and all software distributed under the License are
	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/*
	23	* Copyright (c) 1983, 1993
	24	* The Regents of the University of California. All rights reserved.
	25	*
	26	* Redistribution and use in source and binary forms, with or without
	27	* modification, are permitted provided that the following conditions
	28	* are met:
	29	* 1. Redistributions of source code must retain the above copyright
	30	* notice, this list of conditions and the following disclaimer.
	31	* 2. Redistributions in binary form must reproduce the above copyright
	32	* notice, this list of conditions and the following disclaimer in the
	33	* documentation and/or other materials provided with the distribution.
	34	* 3. All advertising materials mentioning features or use of this software
	35	* must display the following acknowledgement:
	36	* This product includes software developed by the University of
	37	* California, Berkeley and its contributors.
	38	* 4. Neither the name of the University nor the names of its contributors
	39	* may be used to endorse or promote products derived from this software
	40	* without specific prior written permission.
	41	*
	42	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	43	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	44	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	45	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	46	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	47	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	48	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	49	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	50	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	51	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	52	* SUCH DAMAGE.
	53	*/
	54
	55
	56	#include <sys/param.h>
	57	#include <dirent.h>
	58	#include <stdlib.h>
	59	#include <unistd.h>
	60
	61	/*
	62	* The option SINGLEUSE may be defined to say that a telldir
	63	* cookie may be used only once before it is freed. This option
	64	* is used to avoid having memory usage grow without bound.
	65	*/
	66	#define SINGLEUSE
	67
	68	/*
	69	* One of these structures is malloced to describe the current directory
	70	* position each time telldir is called. It records the current magic
	71	* cookie returned by getdirentries and the offset within the buffer
	72	* associated with that return value.
	73	*/
	74	struct ddloc {
	75	struct ddloc loc_next;/ next structure in list */
	76	long loc_index; /* key associated with structure */
	77	long loc_seek; /* magic cookie returned by getdirentries */
	78	long loc_loc; /* offset of entry in buffer */
	79	};
	80
	81	#define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */
	82	#define LOCHASH(i) ((i)&(NDIRHASH-1))
	83
	84	static long dd_loccnt; /* Index of entry for sequential readdir's */
	85	static struct ddloc dd_hash[NDIRHASH]; / Hash list heads for ddlocs */
	86
	87	/*
	88	* return a pointer into a directory
	89	*/
	90	long
	91	telldir(dirp)
	92	const DIR *dirp;
	93	{
	94	register int index;
	95	register struct ddloc *lp;
	96
	97	if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
	98	return (-1);
	99	index = dd_loccnt++;
	100	lp->loc_index = index;
	101	lp->loc_seek = dirp->dd_seek;
	102	lp->loc_loc = dirp->dd_loc;
	103	lp->loc_next = dd_hash[LOCHASH(index)];
	104	dd_hash[LOCHASH(index)] = lp;
	105	return (index);
	106	}
	107
	108	/*
	109	* seek to an entry in a directory.
	110	* Only values returned by "telldir" should be passed to seekdir.
	111	*/
	112	void
	113	_seekdir(dirp, loc)
	114	register DIR *dirp;
	115	long loc;
	116	{
	117	register struct ddloc *lp;
	118	register struct ddloc **prevlp;
	119	struct dirent *dp;
	120
	121	prevlp = &dd_hash[LOCHASH(loc)];
	122	lp = *prevlp;
	123	while (lp != NULL) {
	124	if (lp->loc_index == loc)
	125	break;
	126	prevlp = &lp->loc_next;
	127	lp = lp->loc_next;
	128	}
	129	if (lp == NULL)
	130	return;
	131	if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
	132	goto found;
	133	(void) lseek(dirp->dd_fd, (off_t)lp->loc_seek, SEEK_SET);
	134	dirp->dd_seek = lp->loc_seek;
	135	dirp->dd_loc = 0;
	136	while (dirp->dd_loc < lp->loc_loc) {
	137	dp = readdir(dirp);
	138	if (dp == NULL)
	139	break;
	140	}
	141	found:
	142	#ifdef SINGLEUSE
	143	*prevlp = lp->loc_next;
	144	free((caddr_t)lp);
	145	#endif
	146	}