130 lines
3.7 KiB
C
130 lines
3.7 KiB
C
/*
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* Derived from Berkeley source code. Those parts are
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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 are permitted
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* provided that: (1) source distributions retain this entire copyright
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* notice and comment, and (2) distributions including binaries display
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* the following acknowledgement: ``This product includes software
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* developed by the University of California, Berkeley and its contributors''
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* in the documentation or other materials provided with the distribution
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* and in all advertising materials mentioning features or use of this
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* software. Neither the name of the University nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)telldir.c 5.8 (Berkeley) 6/1/90";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/param.h>
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#include <pmachine.h>
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#include <stdlib.h> /* For malloc and free */
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#ifdef USE_SYS_DIR_H
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#include <sys/dir.h>
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#else
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#include <dirent.h>
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#endif
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#if defined(AIX) && defined(__GNUC__) /* lucb */
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#define dd_bsize dd_size
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#endif
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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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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_bbase;
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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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p__seekdir(register DIR *dirp, 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_bbase)
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goto found;
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if(dirp->dd_fd < 0)
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p__seekvdir(dirp->dd_fd,lp->loc_seek);
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else
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(void) lseek(dirp->dd_fd, lp->loc_seek, 0);
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dirp->dd_bbase = 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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assert(P_IS_THIS_THREAD_MASTER()); /*SOLARIS: readdir MT-Unsafe */
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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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