1 /* replacement pread function
2 Copyright (C) 2009-2018 Free Software Foundation, Inc.
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
24 #define __libc_lseek(f,o,w) lseek (f, o, w)
25 #define __set_errno(Val) errno = (Val)
26 #define __libc_read(f,b,n) read (f, b, n)
28 /* pread substitute for systems that the function, such as mingw32 and BeOS. */
29 /* The following is identical to the function from glibc's
30 sysdeps/posix/pread.c */
32 /* Note: This implementation of pread is not multithread-safe. */
35 pread (int fd
, void *buf
, size_t nbyte
, off_t offset
)
37 /* Since we must not change the file pointer preserve the value so that
38 we can restore it later. */
41 off_t old_offset
= __libc_lseek (fd
, 0, SEEK_CUR
);
42 if (old_offset
== (off_t
) -1)
45 /* Set to wanted position. */
46 if (__libc_lseek (fd
, offset
, SEEK_SET
) == (off_t
) -1)
49 /* Write out the data. */
50 result
= __libc_read (fd
, buf
, nbyte
);
52 /* Now we have to restore the position. If this fails we have to
53 return this as an error. But if the writing also failed we
56 if (__libc_lseek (fd
, old_offset
, SEEK_SET
) == (off_t
) -1)
59 __set_errno (save_errno
);
62 __set_errno (save_errno
);