1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
/* Emulate flock on platforms that lack it, primarily Windows and MinGW.
This is derived from sqlite3 sources.
https://www.sqlite.org/src/finfo?name=src/os_win.c
https://www.sqlite.org/copyright.html
Written by Richard W.M. Jones <rjones.at.redhat.com>
Copyright (C) 2008-2023 Free Software Foundation, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include <sys/file.h>
#if defined _WIN32 && ! defined __CYGWIN__
/* LockFileEx */
# define WIN32_LEAN_AND_MEAN
# include <windows.h>
# include <errno.h>
/* _get_osfhandle */
# if GNULIB_MSVC_NOTHROW
# include "msvc-nothrow.h"
# else
# include <io.h>
# endif
/* Determine the current size of a file. Because the other braindead
* APIs we'll call need lower/upper 32 bit pairs, keep the file size
* like that too.
*/
static BOOL
file_size (HANDLE h, DWORD * lower, DWORD * upper)
{
*lower = GetFileSize (h, upper);
return 1;
}
/* LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems. */
# ifndef LOCKFILE_FAIL_IMMEDIATELY
# define LOCKFILE_FAIL_IMMEDIATELY 1
# endif
/* Acquire a lock. */
static BOOL
do_lock (HANDLE h, int non_blocking, int exclusive)
{
BOOL res;
DWORD size_lower, size_upper;
OVERLAPPED ovlp;
int flags = 0;
/* We're going to lock the whole file, so get the file size. */
res = file_size (h, &size_lower, &size_upper);
if (!res)
return 0;
/* Start offset is 0, and also zero the remaining members of this struct. */
memset (&ovlp, 0, sizeof ovlp);
if (non_blocking)
flags |= LOCKFILE_FAIL_IMMEDIATELY;
if (exclusive)
flags |= LOCKFILE_EXCLUSIVE_LOCK;
return LockFileEx (h, flags, 0, size_lower, size_upper, &ovlp);
}
/* Unlock reader or exclusive lock. */
static BOOL
do_unlock (HANDLE h)
{
int res;
DWORD size_lower, size_upper;
res = file_size (h, &size_lower, &size_upper);
if (!res)
return 0;
return UnlockFile (h, 0, 0, size_lower, size_upper);
}
/* Now our BSD-like flock operation. */
int
flock (int fd, int operation)
{
HANDLE h = (HANDLE) _get_osfhandle (fd);
DWORD res;
int non_blocking;
if (h == INVALID_HANDLE_VALUE)
{
errno = EBADF;
return -1;
}
non_blocking = operation & LOCK_NB;
operation &= ~LOCK_NB;
switch (operation)
{
case LOCK_SH:
res = do_lock (h, non_blocking, 0);
break;
case LOCK_EX:
res = do_lock (h, non_blocking, 1);
break;
case LOCK_UN:
res = do_unlock (h);
break;
default:
errno = EINVAL;
return -1;
}
/* Map Windows errors into Unix errnos. As usual MSDN fails to
* document the permissible error codes.
*/
if (!res)
{
DWORD err = GetLastError ();
switch (err)
{
/* This means someone else is holding a lock. */
case ERROR_LOCK_VIOLATION:
errno = EAGAIN;
break;
/* Out of memory. */
case ERROR_NOT_ENOUGH_MEMORY:
errno = ENOMEM;
break;
case ERROR_BAD_COMMAND:
errno = EINVAL;
break;
/* Unlikely to be other errors, but at least don't lose the
* error code.
*/
default:
errno = err;
}
return -1;
}
return 0;
}
#else /* !Windows */
# ifdef HAVE_STRUCT_FLOCK_L_TYPE
/* We know how to implement flock in terms of fcntl. */
# include <fcntl.h>
# ifdef HAVE_UNISTD_H
# include <unistd.h>
# endif
# include <errno.h>
# include <string.h>
int
flock (int fd, int operation)
{
int cmd, r;
struct flock fl;
if (operation & LOCK_NB)
cmd = F_SETLK;
else
cmd = F_SETLKW;
operation &= ~LOCK_NB;
memset (&fl, 0, sizeof fl);
fl.l_whence = SEEK_SET;
/* l_start & l_len are 0, which as a special case means "whole file". */
switch (operation)
{
case LOCK_SH:
fl.l_type = F_RDLCK;
break;
case LOCK_EX:
fl.l_type = F_WRLCK;
break;
case LOCK_UN:
fl.l_type = F_UNLCK;
break;
default:
errno = EINVAL;
return -1;
}
r = fcntl (fd, cmd, &fl);
if (r == -1 && errno == EACCES)
errno = EAGAIN;
return r;
}
# else /* !HAVE_STRUCT_FLOCK_L_TYPE */
# error "This platform lacks flock function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib."
# endif /* !HAVE_STRUCT_FLOCK_L_TYPE */
#endif /* !Windows */
|
