diff options
Diffstat (limited to 'REORG.TODO/sysdeps/posix/pread.c')
-rw-r--r-- | REORG.TODO/sysdeps/posix/pread.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/posix/pread.c b/REORG.TODO/sysdeps/posix/pread.c new file mode 100644 index 0000000000..82d6d9c7d9 --- /dev/null +++ b/REORG.TODO/sysdeps/posix/pread.c @@ -0,0 +1,62 @@ +/* Read block from given position in file without changing file pointer. + POSIX version. + Copyright (C) 1997-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. + + The GNU C 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. + + The GNU C 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 the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <errno.h> +#include <unistd.h> + +/* Note: This implementation of pread is not multithread-safe. */ + +ssize_t +__libc_pread (int fd, void *buf, size_t nbyte, off_t offset) +{ + /* Since we must not change the file pointer preserve the value so that + we can restore it later. */ + int save_errno; + ssize_t result; + off_t old_offset = __libc_lseek (fd, 0, SEEK_CUR); + if (old_offset == (off_t) -1) + return -1; + + /* Set to wanted position. */ + if (__libc_lseek (fd, offset, SEEK_SET) == (off_t) -1) + return -1; + + /* Write out the data. */ + result = __libc_read (fd, buf, nbyte); + + /* Now we have to restore the position. If this fails we have to + return this as an error. But if the writing also failed we + return this error. */ + save_errno = errno; + if (__libc_lseek (fd, old_offset, SEEK_SET) == (off_t) -1) + { + if (result == -1) + __set_errno (save_errno); + return -1; + } + __set_errno (save_errno); + + return result; +} + +#ifndef __libc_pread +strong_alias (__libc_pread, __pread) +weak_alias (__libc_pread, pread) +#endif |