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authorRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
committerRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
commit28f540f45bbacd939bfd07f213bcad2bf730b1bf (patch)
tree15f07c4c43d635959c6afee96bde71fb1b3614ee /sysdeps/unix/bsd/telldir.c
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initial import
Diffstat (limited to 'sysdeps/unix/bsd/telldir.c')
-rw-r--r--sysdeps/unix/bsd/telldir.c93
1 files changed, 93 insertions, 0 deletions
diff --git a/sysdeps/unix/bsd/telldir.c b/sysdeps/unix/bsd/telldir.c
new file mode 100644
index 0000000000..0321f954b8
--- /dev/null
+++ b/sysdeps/unix/bsd/telldir.c
@@ -0,0 +1,93 @@
+/* Copyright (C) 1994 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA. */
+
+#include <ansidecl.h>
+#include <errno.h>
+#include <stddef.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <stdlib.h>
+
+/* Internal data structure for telldir and seekdir. */
+struct record
+ {
+ struct record *next; /* Link in chain. */
+ off_t cookie; /* Value returned by `telldir'. */
+ off_t pos;
+ size_t offset;
+ };
+#define NBUCKETS 32
+static struct record *records[32];
+static off_t lastpos;
+
+
+/* Return the current position of DIRP. */
+off_t
+DEFUN(telldir, (dirp), DIR *dirp)
+{
+ struct record *new;
+
+ new = malloc (sizeof *new);
+ if (new == NULL)
+ return (off_t) -1;
+
+ new->pos = dirp->__pos;
+ new->offset = dirp->__offset;
+ new->cookie = ++lastpos;
+ new->next = records[new->cookie % NBUCKETS];
+ records[new->cookie % NBUCKETS] = new;
+
+ return new->cookie;
+}
+
+
+
+/* Seek to position POS in DIRP. */
+void
+DEFUN(seekdir, (dirp, pos), DIR *dirp AND __off_t pos)
+{
+ struct record *r, **prevr;
+
+ for (prevr = &records[pos % NBUCKETS], r = *prevr;
+ r != NULL;
+ prevr = &r->next, r = r->next)
+ if (r->cookie == pos)
+ {
+ if (dirp->__pos != r->pos || dirp->__offset != r->offset)
+ {
+ dirp->__size = 0; /* Must read a fresh buffer. */
+ /* Move to the saved position. */
+ __lseek (dirp->__fd, r->pos, SEEK_SET);
+ dirp->__pos = r->pos;
+ dirp->__offset = 0;
+ /* Read entries until we reach the saved offset. */
+ while (dirp->__offset < r->offset)
+ if (readdir (dirp) == NULL)
+ break;
+ }
+
+ /* To prevent leaking memory, cookies returned from telldir
+ can only be used once. So free this one's record now. */
+ *prevr = r->next;
+ free (r);
+ return;
+ }
+
+ /* We lost, but have no way to indicate it. Oh well. */
+}