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116 lines
2.8 KiB
C
116 lines
2.8 KiB
C
/* Copyright (C) 1994-2013 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stddef.h>
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#include <dirent.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <stdlib.h>
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#include "dirstream.h"
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/* Internal data structure for telldir and seekdir. */
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struct record
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{
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struct record *next; /* Link in chain. */
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off_t cookie; /* Value returned by `telldir'. */
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off_t pos;
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size_t offset;
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};
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#define NBUCKETS 32
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static struct record *records[32];
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static off_t lastpos;
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__libc_lock_define_initialized(static, lock) /* Locks above data. */
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/* Return the current position of DIRP. */
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long int
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telldir (dirp)
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DIR *dirp;
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{
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struct record *new;
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long int pos;
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new = malloc (sizeof *new);
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if (new == NULL)
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return -1l;
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__libc_lock_lock (lock);
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new->pos = dirp->filepos;
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new->offset = dirp->offset;
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new->cookie = ++lastpos;
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new->next = records[new->cookie % NBUCKETS];
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records[new->cookie % NBUCKETS] = new;
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pos = new->cookie;
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__libc_lock_unlock (lock);
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return pos;
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}
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/* Seek to position POS in DIRP. */
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void
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seekdir (dirp, pos)
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DIR *dirp;
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long int pos;
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{
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struct record *r, **prevr;
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__libc_lock_lock (lock);
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for (prevr = &records[pos % NBUCKETS], r = *prevr;
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r != NULL;
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prevr = &r->next, r = r->next)
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if (r->cookie == pos)
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{
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__libc_lock_lock (dirp->__lock);
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if (dirp->filepos != r->pos || dirp->offset != r->offset)
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{
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dirp->size = 0; /* Must read a fresh buffer. */
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/* Move to the saved position. */
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__lseek (dirp->fd, r->pos, SEEK_SET);
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dirp->filepos = r->pos;
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dirp->offset = 0;
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/* Read entries until we reach the saved offset. */
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while (dirp->offset < r->offset)
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{
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struct dirent *scan;
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__libc_lock_unlock (dirp->__lock);
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scan = readdir (dirp);
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__libc_lock_lock (dirp->__lock);
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if (! scan)
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break;
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}
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}
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__libc_lock_unlock (dirp->__lock);
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/* To prevent leaking memory, cookies returned from telldir
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can only be used once. So free this one's record now. */
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*prevr = r->next;
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free (r);
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break;
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}
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__libc_lock_unlock (lock);
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/* If we lost there is no way to indicate it. Oh well. */
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}
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