| xf.li | bdd93d5 | 2023-05-12 07:10:14 -0700 | [diff] [blame^] | 1 | /* Write block to given position in file without changing file pointer. |
| 2 | POSIX version. |
| 3 | Copyright (C) 1997-2016 Free Software Foundation, Inc. |
| 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 |
| 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. |
| 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 |
| 15 | Lesser General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU Lesser General Public |
| 18 | License along with the GNU C Library; if not, see |
| 19 | <http://www.gnu.org/licenses/>. */ |
| 20 | |
| 21 | #include <errno.h> |
| 22 | #include <unistd.h> |
| 23 | |
| 24 | /* Note: This implementation of pwrite is not multithread-safe. */ |
| 25 | |
| 26 | ssize_t |
| 27 | __libc_pwrite (int fd, const void *buf, size_t nbyte, off_t offset) |
| 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; |
| 33 | off_t old_offset = __libc_lseek (fd, 0, SEEK_CUR); |
| 34 | if (old_offset == (off_t) -1) |
| 35 | return -1; |
| 36 | |
| 37 | /* Set to wanted position. */ |
| 38 | if (__libc_lseek (fd, offset, SEEK_SET) == (off_t) -1) |
| 39 | return -1; |
| 40 | |
| 41 | /* Write out the data. */ |
| 42 | result = __libc_write (fd, buf, nbyte); |
| 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; |
| 48 | if (__libc_lseek (fd, old_offset, SEEK_SET) == (off_t) -1) |
| 49 | { |
| 50 | if (result == -1) |
| 51 | __set_errno (save_errno); |
| 52 | return -1; |
| 53 | } |
| 54 | __set_errno (save_errno); |
| 55 | |
| 56 | return result; |
| 57 | } |
| 58 | |
| 59 | #ifndef __libc_pwrite |
| 60 | strong_alias (__libc_pwrite, __pwrite) |
| 61 | weak_alias (__libc_pwrite, pwrite) |
| 62 | #endif |