Home | History | Annotate | Line # | Download | only in compat
pread.c revision 1.4 
      1 /*	$NetBSD: pread.c,v 1.4 2008/04/28 20:24:12 martin Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2001 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Todd Vierling.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 /* Emulate pread() with lseek()/read()/lseek(). Not thread-safe, of course. */
     33 
     34 #include "nbtool_config.h"
     35 
     36 #if !HAVE_PREAD
     37 #include <unistd.h>
     38 
     39 ssize_t pread(int d, void *buf, size_t nbytes, off_t offset) {
     40 	off_t oldoff = lseek(d, offset, SEEK_SET);
     41 	int olderrno;
     42 	ssize_t nr;
     43 
     44 	if (oldoff < 0)
     45 		return -1;
     46 
     47 	nr = read(d, buf, nbytes);
     48 
     49 	olderrno = errno;
     50 	lseek(d, oldoff, SEEK_SET);
     51 	errno = olderrno;
     52 
     53 	return nr;
     54 }
     55 #endif
     56