diff options
Diffstat (limited to 'lib/libc/gen/telldir.c')
| -rw-r--r-- | lib/libc/gen/telldir.c | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/lib/libc/gen/telldir.c b/lib/libc/gen/telldir.c new file mode 100644 index 000000000000..1731cc4d7a2c --- /dev/null +++ b/lib/libc/gen/telldir.c @@ -0,0 +1,204 @@ +/*- + * SPDX-License-Identifier: BSD-3-Clause + * + * Copyright (c) 1983, 1993 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include "namespace.h" +#include <sys/param.h> +#include <sys/queue.h> +#include <dirent.h> +#include <pthread.h> +#include <stdlib.h> +#include <unistd.h> +#include "un-namespace.h" + +#include "libc_private.h" +#include "gen-private.h" +#include "telldir.h" + +/* + * return a pointer into a directory + */ +long +telldir(DIR *dirp) +{ + struct ddloc_mem *lp, *flp; + union ddloc_packed ddloc; + + if (__isthreaded) + _pthread_mutex_lock(&dirp->dd_lock); + /* + * Outline: + * 1) If the directory position fits in a packed structure, return that. + * 2) Otherwise, see if it's already been recorded in the linked list + * 3) Otherwise, malloc a new one + */ + if (dirp->dd_seek < (off_t)(1l << DD_SEEK_BITS) && + dirp->dd_loc < (1l << DD_LOC_BITS)) { + ddloc.s.is_packed = 1; + ddloc.s.loc = dirp->dd_loc; + ddloc.s.seek = dirp->dd_seek; + goto out; + } + + flp = NULL; + LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) { + if (lp->loc_seek == dirp->dd_seek) { + if (flp == NULL) + flp = lp; + if (lp->loc_loc == dirp->dd_loc) + break; + } else if (flp != NULL) { + lp = NULL; + break; + } + } + if (lp == NULL) { + lp = malloc(sizeof(struct ddloc_mem)); + if (lp == NULL) { + if (__isthreaded) + _pthread_mutex_unlock(&dirp->dd_lock); + return (-1); + } + lp->loc_index = dirp->dd_td->td_loccnt++; + lp->loc_seek = dirp->dd_seek; + lp->loc_loc = dirp->dd_loc; + if (flp != NULL) + LIST_INSERT_BEFORE(flp, lp, loc_lqe); + else + LIST_INSERT_HEAD(&dirp->dd_td->td_locq, lp, loc_lqe); + } + ddloc.i.is_packed = 0; + /* + * Technically this assignment could overflow on 32-bit architectures, + * but we would get ENOMEM long before that happens. + */ + ddloc.i.index = lp->loc_index; + +out: + if (__isthreaded) + _pthread_mutex_unlock(&dirp->dd_lock); + return (ddloc.l); +} + +/* + * seek to an entry in a directory. + * Only values returned by "telldir" should be passed to seekdir. + */ +void +_seekdir(DIR *dirp, long loc) +{ + struct ddloc_mem *lp; + struct dirent *dp; + union ddloc_packed ddloc; + off_t loc_seek; + size_t loc_loc; + + ddloc.l = loc; + + if (ddloc.s.is_packed) { + loc_seek = ddloc.s.seek; + loc_loc = ddloc.s.loc; + } else { + LIST_FOREACH(lp, &dirp->dd_td->td_locq, loc_lqe) { + if (lp->loc_index == ddloc.i.index) + break; + } + if (lp == NULL) + return; + + loc_seek = lp->loc_seek; + loc_loc = lp->loc_loc; + } + if (loc_loc == dirp->dd_loc && loc_seek == dirp->dd_seek) + return; + + /* If it's within the same chunk of data, don't bother reloading. */ + if (loc_seek == dirp->dd_seek) { + /* + * If we go back to 0 don't make the next readdir + * trigger a call to getdirentries(). + */ + if (loc_loc == 0) + dirp->dd_flags |= __DTF_SKIPREAD; + dirp->dd_loc = loc_loc; + return; + } + (void) lseek(dirp->dd_fd, (off_t)loc_seek, SEEK_SET); + dirp->dd_seek = loc_seek; + dirp->dd_loc = 0; + dirp->dd_flags &= ~__DTF_SKIPREAD; /* current contents are invalid */ + while (dirp->dd_loc < loc_loc) { + dp = _readdir_unlocked(dirp, 0); + if (dp == NULL) + break; + } +} + +/* + * After readdir returns the last entry in a block, a call to telldir + * returns a location that is after the end of that last entry. + * However, that location doesn't refer to a valid directory entry. + * Ideally, the call to telldir would return a location that refers to + * the first entry in the next block. That location is not known + * until the next block is read, so readdir calls this function after + * fetching a new block to fix any such telldir locations. + */ +void +_fixtelldir(DIR *dirp, off_t oldseek, size_t oldloc) +{ + struct ddloc_mem *lp; + + lp = LIST_FIRST(&dirp->dd_td->td_locq); + if (lp != NULL) { + if (lp->loc_loc == oldloc && + lp->loc_seek == oldseek) { + lp->loc_seek = dirp->dd_seek; + lp->loc_loc = dirp->dd_loc; + } + } +} + +/* + * Reclaim memory for telldir cookies which weren't used. + */ +void +_reclaim_telldir(DIR *dirp) +{ + struct ddloc_mem *lp; + struct ddloc_mem *templp; + + lp = LIST_FIRST(&dirp->dd_td->td_locq); + while (lp != NULL) { + templp = lp; + lp = LIST_NEXT(lp, loc_lqe); + free(templp); + } + LIST_INIT(&dirp->dd_td->td_locq); +} |