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 systems
25
26  This is needed because the existing directory handling in FreeBSD
27  and OpenBSD (and possibly NetBSD) doesn't correctly handle unlink()
28  on files in a directory where telldir() has been used. On a block
29  boundary it will occasionally miss a file when seekdir() is used to
30  return to a position previously recorded with telldir().
31
32  This also fixes a severe performance and memory usage problem with
33  telldir() on BSD systems. Each call to telldir() in BSD adds an
34  entry to a linked list, and those entries are cleaned up on
35  closedir(). This means with a large directory closedir() can take an
36  arbitrary amount of time, causing network timeouts as millions of
37  telldir() entries are freed
38
39  Note! This replacement code is not portable. It relies on getdents()
40  always leaving the file descriptor at a seek offset that is a
41  multiple of DIR_BUF_SIZE. If the code detects that this doesn't
42  happen then it will abort(). It also does not handle directories
43  with offsets larger than can be stored in a long,
44
45  This code is available under other free software licenses as
46  well. Contact the author.
47*/
48
49#include <stdlib.h>
50#include <sys/stat.h>
51#include <unistd.h>
52#include <sys/types.h>
53#include <errno.h>
54#include <fcntl.h>
55#include <dirent.h>
56
57#define DIR_BUF_BITS 9
58#define DIR_BUF_SIZE (1<<DIR_BUF_BITS)
59
60struct dir_buf {
61	int fd;
62	int nbytes, ofs;
63	off_t seekpos;
64	char buf[DIR_BUF_SIZE];
65};
66
67DIR *opendir(const char *dname)
68{
69	struct dir_buf *d;
70	struct stat sb;
71	d = malloc(sizeof(*d));
72	if (d == NULL) {
73		errno = ENOMEM;
74		return NULL;
75	}
76	d->fd = open(dname, O_RDONLY);
77	if (d->fd == -1) {
78		free(d);
79		return NULL;
80	}
81	if (fstat(d->fd, &sb) < 0) {
82		close(d->fd);
83		free(d);
84		return NULL;
85	}
86	if (!S_ISDIR(sb.st_mode)) {
87		close(d->fd);
88		free(d);
89		errno = ENOTDIR;
90		return NULL;
91	}
92	d->ofs = 0;
93	d->seekpos = 0;
94	d->nbytes = 0;
95	return (DIR *)d;
96}
97
98struct dirent *readdir(DIR *dir)
99{
100	struct dir_buf *d = (struct dir_buf *)dir;
101	struct dirent *de;
102
103	if (d->ofs >= d->nbytes) {
104		d->seekpos = lseek(d->fd, 0, SEEK_CUR);
105		d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE);
106		d->ofs = 0;
107	}
108	if (d->ofs >= d->nbytes) {
109		return NULL;
110	}
111	de = (struct dirent *)&d->buf[d->ofs];
112	d->ofs += de->d_reclen;
113	return de;
114}
115
116long telldir(DIR *dir)
117{
118	struct dir_buf *d = (struct dir_buf *)dir;
119	if (d->ofs >= d->nbytes) {
120		d->seekpos = lseek(d->fd, 0, SEEK_CUR);
121		d->ofs = 0;
122		d->nbytes = 0;
123	}
124	/* this relies on seekpos always being a multiple of
125	   DIR_BUF_SIZE. Is that always true on BSD systems? */
126	if (d->seekpos & (DIR_BUF_SIZE-1)) {
127		abort();
128	}
129	return d->seekpos + d->ofs;
130}
131
132void seekdir(DIR *dir, long ofs)
133{
134	struct dir_buf *d = (struct dir_buf *)dir;
135	d->seekpos = lseek(d->fd, ofs & ~(DIR_BUF_SIZE-1), SEEK_SET);
136	d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE);
137	d->ofs = 0;
138	while (d->ofs < (ofs & (DIR_BUF_SIZE-1))) {
139		if (readdir(dir) == NULL) break;
140	}
141}
142
143void rewinddir(DIR *dir)
144{
145	seekdir(dir, 0);
146}
147
148int closedir(DIR *dir)
149{
150	struct dir_buf *d = (struct dir_buf *)dir;
151	int r = close(d->fd);
152	if (r != 0) {
153		return r;
154	}
155	free(d);
156	return 0;
157}
158
159#ifndef dirfd
160/* darn, this is a macro on some systems. */
161int dirfd(DIR *dir)
162{
163	struct dir_buf *d = (struct dir_buf *)dir;
164	return d->fd;
165}
166#endif
167