1/*
2   Unix SMB/CIFS implementation.
3
4   Copyright (C) Andrew Tridgell 2005
5
6     ** NOTE! The following LGPL license applies to the replace
7     ** library. This does NOT imply that all of Samba is released
8     ** under the LGPL
9
10   This library is free software; you can redistribute it and/or
11   modify it under the terms of the GNU Lesser General Public
12   License as published by the Free Software Foundation; either
13   version 3 of the License, or (at your option) any later version.
14
15   This library is distributed in the hope that it will be useful,
16   but WITHOUT ANY WARRANTY; without even the implied warranty of
17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18   Lesser General Public License for more details.
19
20   You should have received a copy of the GNU Lesser General Public
21   License along with this library; if not, see <http://www.gnu.org/licenses/>.
22*/
23/*
24  a replacement for opendir/readdir/telldir/seekdir/closedir for BSD
25  systems using getdirentries
26
27  This is needed because the existing directory handling in FreeBSD
28  and OpenBSD (and possibly NetBSD) doesn't correctly handle unlink()
29  on files in a directory where telldir() has been used. On a block
30  boundary it will occasionally miss a file when seekdir() is used to
31  return to a position previously recorded with telldir().
32
33  This also fixes a severe performance and memory usage problem with
34  telldir() on BSD systems. Each call to telldir() in BSD adds an
35  entry to a linked list, and those entries are cleaned up on
36  closedir(). This means with a large directory closedir() can take an
37  arbitrary amount of time, causing network timeouts as millions of
38  telldir() entries are freed
39
40  Note! This replacement code is not portable. It relies on
41  getdirentries() always leaving the file descriptor at a seek offset
42  that is a multiple of DIR_BUF_SIZE. If the code detects that this
43  doesn't happen then it will abort(). It also does not handle
44  directories with offsets larger than can be stored in a long,
45
46  This code is available under other free software licenses as
47  well. Contact the author.
48*/
49
50#include "replace.h"
51#include <stdlib.h>
52#include <sys/stat.h>
53#include <unistd.h>
54#include <sys/types.h>
55#include <errno.h>
56#include <fcntl.h>
57#include <dirent.h>
58
59#define DIR_BUF_BITS 9
60#define DIR_BUF_SIZE (1<<DIR_BUF_BITS)
61
62struct dir_buf {
63	int fd;
64	int nbytes, ofs;
65	off_t seekpos;
66	char buf[DIR_BUF_SIZE];
67};
68
69DIR *opendir(const char *dname)
70{
71	struct dir_buf *d;
72	struct stat sb;
73	d = malloc(sizeof(*d));
74	if (d == NULL) {
75		errno = ENOMEM;
76		return NULL;
77	}
78	d->fd = open(dname, O_RDONLY);
79	if (d->fd == -1) {
80		free(d);
81		return NULL;
82	}
83	if (fstat(d->fd, &sb) < 0) {
84		close(d->fd);
85		free(d);
86		return NULL;
87	}
88	if (!S_ISDIR(sb.st_mode)) {
89		close(d->fd);
90		free(d);
91		errno = ENOTDIR;
92		return NULL;
93	}
94	d->ofs = 0;
95	d->seekpos = 0;
96	d->nbytes = 0;
97	return (DIR *)d;
98}
99
100struct dirent *readdir(DIR *dir)
101{
102	struct dir_buf *d = (struct dir_buf *)dir;
103	struct dirent *de;
104
105	if (d->ofs >= d->nbytes) {
106		long pos;
107		d->nbytes = getdirentries(d->fd, d->buf, DIR_BUF_SIZE, &pos);
108		d->seekpos = pos;
109		d->ofs = 0;
110	}
111	if (d->ofs >= d->nbytes) {
112		return NULL;
113	}
114	de = (struct dirent *)&d->buf[d->ofs];
115	d->ofs += de->d_reclen;
116	return de;
117}
118
119#ifdef TELLDIR_TAKES_CONST_DIR
120long telldir(const DIR *dir)
121#else
122long telldir(DIR *dir)
123#endif
124{
125	struct dir_buf *d = (struct dir_buf *)dir;
126	if (d->ofs >= d->nbytes) {
127		d->seekpos = lseek(d->fd, 0, SEEK_CUR);
128		d->ofs = 0;
129		d->nbytes = 0;
130	}
131	/* this relies on seekpos always being a multiple of
132	   DIR_BUF_SIZE. Is that always true on BSD systems? */
133	if (d->seekpos & (DIR_BUF_SIZE-1)) {
134		abort();
135	}
136	return d->seekpos + d->ofs;
137}
138
139#ifdef SEEKDIR_RETURNS_INT
140int seekdir(DIR *dir, long ofs)
141#else
142void seekdir(DIR *dir, long ofs)
143#endif
144{
145	struct dir_buf *d = (struct dir_buf *)dir;
146	long pos;
147	d->seekpos = lseek(d->fd, ofs & ~(DIR_BUF_SIZE-1), SEEK_SET);
148	d->nbytes = getdirentries(d->fd, d->buf, DIR_BUF_SIZE, &pos);
149	d->ofs = 0;
150	while (d->ofs < (ofs & (DIR_BUF_SIZE-1))) {
151		if (readdir(dir) == NULL) break;
152	}
153#ifdef SEEKDIR_RETURNS_INT
154	return -1;
155#endif
156}
157
158void rewinddir(DIR *dir)
159{
160	seekdir(dir, 0);
161}
162
163int closedir(DIR *dir)
164{
165	struct dir_buf *d = (struct dir_buf *)dir;
166	int r = close(d->fd);
167	if (r != 0) {
168		return r;
169	}
170	free(d);
171	return 0;
172}
173
174#ifndef dirfd
175/* darn, this is a macro on some systems. */
176int dirfd(DIR *dir)
177{
178	struct dir_buf *d = (struct dir_buf *)dir;
179	return d->fd;
180}
181#endif
182
183
184