diff options
Diffstat (limited to 'sysdeps/posix')
| -rw-r--r-- | sysdeps/posix/pread.c | 56 | ||||
| -rw-r--r-- | sysdeps/posix/pwrite.c | 56 |
2 files changed, 112 insertions, 0 deletions
diff --git a/sysdeps/posix/pread.c b/sysdeps/posix/pread.c new file mode 100644 index 0000000000..300aabac65 --- /dev/null +++ b/sysdeps/posix/pread.c @@ -0,0 +1,56 @@ +/* Read block from given position in file without changing file pointer. + POSIX version. + Copyright (C) 1997 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 Library General Public License as + published by the Free Software Foundation; either version 2 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 + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include <errno.h> +#include <unistd.h> + +ssize_t +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 = lseek (fd, 0, SEEK_CUR); + if (old_offset == (off_t) -1) + return -1; + + /* Set to wanted position. */ + if (lseek (fd, offset, SEEK_SET) == (off_t) -1) + return -1; + + /* Write out the data. */ + result = 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 (lseek (fd, old_offset, SEEK_SET) == (off_t) -1) + { + if (result == -1) + __set_errno (save_errno); + return -1; + } + __set_errno (save_errno); + + return result; +} diff --git a/sysdeps/posix/pwrite.c b/sysdeps/posix/pwrite.c new file mode 100644 index 0000000000..7c1ed45cca --- /dev/null +++ b/sysdeps/posix/pwrite.c @@ -0,0 +1,56 @@ +/* Write block to given position in file without changing file pointer. + POSIX version. + Copyright (C) 1997 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 Library General Public License as + published by the Free Software Foundation; either version 2 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 + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include <errno.h> +#include <unistd.h> + +ssize_t +pwrite (int fd, const 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 = lseek (fd, 0, SEEK_CUR); + if (old_offset == (off_t) -1) + return -1; + + /* Set to wanted position. */ + if (lseek (fd, offset, SEEK_SET) == (off_t) -1) + return -1; + + /* Write out the data. */ + result = write (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 (lseek (fd, old_offset, SEEK_SET) == (off_t) -1) + { + if (result == -1) + __set_errno (save_errno); + return -1; + } + __set_errno (save_errno); + + return result; +} |