130 lines
4.1 KiB
C
130 lines
4.1 KiB
C
/*
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* Copyright (c) 1983 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)telldir.c 5.9 (Berkeley) 2/23/91";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/param.h>
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#include <dirent.h>
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#include <stdlib.h>
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#include <unistd.h>
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/*
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* The option SINGLEUSE may be defined to say that a telldir
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* cookie may be used only once before it is freed. This option
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* is used to avoid having memory usage grow without bound.
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*/
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#define SINGLEUSE
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/*
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* One of these structures is malloced to describe the current directory
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* position each time telldir is called. It records the current magic
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* cookie returned by getdirentries and the offset within the buffer
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* associated with that return value.
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*/
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struct ddloc {
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struct ddloc *loc_next;/* next structure in list */
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long loc_index; /* key associated with structure */
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long loc_seek; /* magic cookie returned by getdirentries */
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long loc_loc; /* offset of entry in buffer */
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};
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#define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */
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#define LOCHASH(i) ((i)&(NDIRHASH-1))
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static long dd_loccnt; /* Index of entry for sequential readdir's */
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static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */
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/*
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* return a pointer into a directory
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*/
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long
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telldir(dirp)
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const DIR *dirp;
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{
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register int index;
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register struct ddloc *lp;
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if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)
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return (-1);
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index = dd_loccnt++;
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lp->loc_index = index;
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lp->loc_seek = dirp->dd_seek;
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lp->loc_loc = dirp->dd_loc;
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lp->loc_next = dd_hash[LOCHASH(index)];
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dd_hash[LOCHASH(index)] = lp;
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return (index);
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}
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/*
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* seek to an entry in a directory.
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* Only values returned by "telldir" should be passed to seekdir.
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*/
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void
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_seekdir(dirp, loc)
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register DIR *dirp;
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long loc;
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{
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register struct ddloc *lp;
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register struct ddloc **prevlp;
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struct dirent *dp;
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extern long lseek();
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prevlp = &dd_hash[LOCHASH(loc)];
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lp = *prevlp;
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while (lp != NULL) {
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if (lp->loc_index == loc)
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break;
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prevlp = &lp->loc_next;
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lp = lp->loc_next;
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}
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if (lp == NULL)
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return;
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if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)
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goto found;
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(void) lseek(dirp->dd_fd, lp->loc_seek, 0);
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dirp->dd_seek = lp->loc_seek;
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dirp->dd_loc = 0;
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while (dirp->dd_loc < lp->loc_loc) {
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dp = readdir(dirp);
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if (dp == NULL)
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break;
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}
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found:
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#ifdef SINGLEUSE
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*prevlp = lp->loc_next;
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free((caddr_t)lp);
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#endif
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}
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