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a5a0310d UD |
1 | /* Write block to given position in file without changing file pointer. |
2 | POSIX version. | |
2b778ceb | 3 | Copyright (C) 1997-2021 Free Software Foundation, Inc. |
a5a0310d UD |
4 | This file is part of the GNU C Library. |
5 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. | |
6 | ||
7 | The GNU C Library is free software; you can redistribute it and/or | |
41bdb6e2 AJ |
8 | modify it under the terms of the GNU Lesser General Public |
9 | License as published by the Free Software Foundation; either | |
10 | version 2.1 of the License, or (at your option) any later version. | |
a5a0310d UD |
11 | |
12 | The GNU C Library is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
41bdb6e2 | 15 | Lesser General Public License for more details. |
a5a0310d | 16 | |
41bdb6e2 | 17 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 | 18 | License along with the GNU C Library; if not, see |
5a82c748 | 19 | <https://www.gnu.org/licenses/>. */ |
a5a0310d UD |
20 | |
21 | #include <errno.h> | |
22 | #include <unistd.h> | |
23 | ||
131c6eb7 RM |
24 | /* Note: This implementation of pwrite is not multithread-safe. */ |
25 | ||
a5a0310d | 26 | ssize_t |
778c59c8 | 27 | __libc_pwrite (int fd, const void *buf, size_t nbyte, off_t offset) |
a5a0310d UD |
28 | { |
29 | /* Since we must not change the file pointer preserve the value so that | |
30 | we can restore it later. */ | |
31 | int save_errno; | |
32 | ssize_t result; | |
778c59c8 | 33 | off_t old_offset = __libc_lseek (fd, 0, SEEK_CUR); |
a5a0310d UD |
34 | if (old_offset == (off_t) -1) |
35 | return -1; | |
36 | ||
37 | /* Set to wanted position. */ | |
778c59c8 | 38 | if (__libc_lseek (fd, offset, SEEK_SET) == (off_t) -1) |
a5a0310d UD |
39 | return -1; |
40 | ||
41 | /* Write out the data. */ | |
778c59c8 | 42 | result = __libc_write (fd, buf, nbyte); |
a5a0310d UD |
43 | |
44 | /* Now we have to restore the position. If this fails we have to | |
45 | return this as an error. But if the writing also failed we | |
46 | return this error. */ | |
47 | save_errno = errno; | |
778c59c8 | 48 | if (__libc_lseek (fd, old_offset, SEEK_SET) == (off_t) -1) |
a5a0310d UD |
49 | { |
50 | if (result == -1) | |
51 | __set_errno (save_errno); | |
52 | return -1; | |
53 | } | |
54 | __set_errno (save_errno); | |
55 | ||
56 | return result; | |
57 | } | |
d71b808a | 58 | |
778c59c8 UD |
59 | #ifndef __libc_pwrite |
60 | strong_alias (__libc_pwrite, __pwrite) | |
61 | weak_alias (__libc_pwrite, pwrite) | |
d71b808a | 62 | #endif |