| 1 | /* Emulate flock on platforms that lack it, primarily Windows and MinGW. |
| 2 | |
| 3 | This is derived from sqlite3 sources. |
| 4 | http://www.sqlite.org/cvstrac/rlog?f=sqlite/src/os_win.c |
| 5 | http://www.sqlite.org/copyright.html |
| 6 | |
| 7 | Written by Richard W.M. Jones <rjones.at.redhat.com> |
| 8 | |
| 9 | Copyright (C) 2008 Free Software Foundation, Inc. |
| 10 | |
| 11 | This library is free software; you can redistribute it and/or |
| 12 | modify it under the terms of the GNU Lesser General Public |
| 13 | License as published by the Free Software Foundation; either |
| 14 | version 2.1 of the License, or (at your option) any later version. |
| 15 | |
| 16 | This library is distributed in the hope that it will be useful, |
| 17 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 19 | Lesser General Public License for more details. |
| 20 | |
| 21 | You should have received a copy of the GNU Lesser General Public License |
| 22 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 23 | |
| 24 | #include <config.h> |
| 25 | #include <sys/file.h> |
| 26 | |
| 27 | #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__ |
| 28 | |
| 29 | /* _get_osfhandle */ |
| 30 | #include <io.h> |
| 31 | |
| 32 | /* LockFileEx */ |
| 33 | #define WIN32_LEAN_AND_MEAN |
| 34 | #include <windows.h> |
| 35 | |
| 36 | #include <errno.h> |
| 37 | |
| 38 | /* Determine the current size of a file. Because the other braindead |
| 39 | * APIs we'll call need lower/upper 32 bit pairs, keep the file size |
| 40 | * like that too. |
| 41 | */ |
| 42 | static BOOL |
| 43 | file_size (HANDLE h, DWORD * lower, DWORD * upper) |
| 44 | { |
| 45 | *lower = GetFileSize (h, upper); |
| 46 | return 1; |
| 47 | } |
| 48 | |
| 49 | /* LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems. */ |
| 50 | #ifndef LOCKFILE_FAIL_IMMEDIATELY |
| 51 | # define LOCKFILE_FAIL_IMMEDIATELY 1 |
| 52 | #endif |
| 53 | |
| 54 | /* Acquire a lock. */ |
| 55 | static BOOL |
| 56 | do_lock (HANDLE h, int non_blocking, int exclusive) |
| 57 | { |
| 58 | BOOL res; |
| 59 | DWORD size_lower, size_upper; |
| 60 | OVERLAPPED ovlp; |
| 61 | int flags = 0; |
| 62 | |
| 63 | /* We're going to lock the whole file, so get the file size. */ |
| 64 | res = file_size (h, &size_lower, &size_upper); |
| 65 | if (!res) |
| 66 | return 0; |
| 67 | |
| 68 | /* Start offset is 0, and also zero the remaining members of this struct. */ |
| 69 | memset (&ovlp, 0, sizeof ovlp); |
| 70 | |
| 71 | if (non_blocking) |
| 72 | flags |= LOCKFILE_FAIL_IMMEDIATELY; |
| 73 | if (exclusive) |
| 74 | flags |= LOCKFILE_EXCLUSIVE_LOCK; |
| 75 | |
| 76 | return LockFileEx (h, flags, 0, size_lower, size_upper, &ovlp); |
| 77 | } |
| 78 | |
| 79 | /* Unlock reader or exclusive lock. */ |
| 80 | static BOOL |
| 81 | do_unlock (HANDLE h) |
| 82 | { |
| 83 | int res; |
| 84 | DWORD size_lower, size_upper; |
| 85 | |
| 86 | res = file_size (h, &size_lower, &size_upper); |
| 87 | if (!res) |
| 88 | return 0; |
| 89 | |
| 90 | return UnlockFile (h, 0, 0, size_lower, size_upper); |
| 91 | } |
| 92 | |
| 93 | /* Now our BSD-like flock operation. */ |
| 94 | int |
| 95 | flock (int fd, int operation) |
| 96 | { |
| 97 | HANDLE h = (HANDLE) _get_osfhandle (fd); |
| 98 | DWORD res; |
| 99 | int non_blocking; |
| 100 | |
| 101 | if (h == INVALID_HANDLE_VALUE) |
| 102 | { |
| 103 | errno = EBADF; |
| 104 | return -1; |
| 105 | } |
| 106 | |
| 107 | non_blocking = operation & LOCK_NB; |
| 108 | operation &= ~LOCK_NB; |
| 109 | |
| 110 | switch (operation) |
| 111 | { |
| 112 | case LOCK_SH: |
| 113 | res = do_lock (h, non_blocking, 0); |
| 114 | break; |
| 115 | case LOCK_EX: |
| 116 | res = do_lock (h, non_blocking, 1); |
| 117 | break; |
| 118 | case LOCK_UN: |
| 119 | res = do_unlock (h); |
| 120 | break; |
| 121 | default: |
| 122 | errno = EINVAL; |
| 123 | return -1; |
| 124 | } |
| 125 | |
| 126 | /* Map Windows errors into Unix errnos. As usual MSDN fails to |
| 127 | * document the permissible error codes. |
| 128 | */ |
| 129 | if (!res) |
| 130 | { |
| 131 | DWORD err = GetLastError (); |
| 132 | switch (err) |
| 133 | { |
| 134 | /* This means someone else is holding a lock. */ |
| 135 | case ERROR_LOCK_VIOLATION: |
| 136 | errno = EAGAIN; |
| 137 | break; |
| 138 | |
| 139 | /* Out of memory. */ |
| 140 | case ERROR_NOT_ENOUGH_MEMORY: |
| 141 | errno = ENOMEM; |
| 142 | break; |
| 143 | |
| 144 | case ERROR_BAD_COMMAND: |
| 145 | errno = EINVAL; |
| 146 | break; |
| 147 | |
| 148 | /* Unlikely to be other errors, but at least don't lose the |
| 149 | * error code. |
| 150 | */ |
| 151 | default: |
| 152 | errno = err; |
| 153 | } |
| 154 | |
| 155 | return -1; |
| 156 | } |
| 157 | |
| 158 | return 0; |
| 159 | } |
| 160 | |
| 161 | #else /* !Windows */ |
| 162 | |
| 163 | #ifdef HAVE_STRUCT_FLOCK_L_TYPE |
| 164 | /* We know how to implement flock in terms of fcntl. */ |
| 165 | |
| 166 | #ifdef HAVE_FCNTL_H |
| 167 | #include <fcntl.h> |
| 168 | #endif |
| 169 | |
| 170 | #ifdef HAVE_UNISTD_H |
| 171 | #include <unistd.h> |
| 172 | #endif |
| 173 | |
| 174 | #include <errno.h> |
| 175 | #include <string.h> |
| 176 | |
| 177 | int |
| 178 | flock (int fd, int operation) |
| 179 | { |
| 180 | int cmd, r; |
| 181 | struct flock fl; |
| 182 | |
| 183 | if (operation & LOCK_NB) |
| 184 | cmd = F_SETLK; |
| 185 | else |
| 186 | cmd = F_SETLKW; |
| 187 | operation &= ~LOCK_NB; |
| 188 | |
| 189 | memset (&fl, 0, sizeof fl); |
| 190 | fl.l_whence = SEEK_SET; |
| 191 | /* l_start & l_len are 0, which as a special case means "whole file". */ |
| 192 | |
| 193 | switch (operation) |
| 194 | { |
| 195 | case LOCK_SH: |
| 196 | fl.l_type = F_RDLCK; |
| 197 | break; |
| 198 | case LOCK_EX: |
| 199 | fl.l_type = F_WRLCK; |
| 200 | break; |
| 201 | case LOCK_UN: |
| 202 | fl.l_type = F_UNLCK; |
| 203 | break; |
| 204 | default: |
| 205 | errno = EINVAL; |
| 206 | return -1; |
| 207 | } |
| 208 | |
| 209 | r = fcntl (fd, cmd, &fl); |
| 210 | if (r == -1 && errno == EACCES) |
| 211 | errno = EAGAIN; |
| 212 | |
| 213 | return r; |
| 214 | } |
| 215 | |
| 216 | #else /* !HAVE_STRUCT_FLOCK_L_TYPE */ |
| 217 | |
| 218 | #error "This platform lacks flock function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib." |
| 219 | |
| 220 | #endif /* !HAVE_STRUCT_FLOCK_L_TYPE */ |
| 221 | |
| 222 | #endif /* !Windows */ |