| /* Read block from given position in file without changing file pointer. |
| POSIX version. |
| Copyright (C) 1997-2014 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 pread64 is not multithread-safe. */ |
| |
| ssize_t |
| __libc_pread64 (int fd, void *buf, size_t nbyte, off64_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; |
| off64_t old_offset = __libc_lseek64 (fd, 0, SEEK_CUR); |
| if (old_offset == (off64_t) -1) |
| return -1; |
| |
| /* Set to wanted position. */ |
| if (__libc_lseek64 (fd, offset, SEEK_SET) == (off64_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_lseek64 (fd, old_offset, SEEK_SET) == (off64_t) -1) |
| { |
| if (result == -1) |
| __set_errno (save_errno); |
| return -1; |
| } |
| __set_errno (save_errno); |
| |
| return result; |
| } |
| |
| #ifndef __libc_pread64 |
| weak_alias (__libc_pread64, __pread64) |
| weak_alias (__libc_pread64, pread64) |
| #endif |
