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pread.c revision 1.8 
      1 /*	$NetBSD: pread.c,v 1.8 2006/11/10 17:37:39 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1992, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: pread.c,v 1.8 2006/11/10 17:37:39 christos Exp $");
     35 #endif /* LIBC_SCCS and not lint */
     36 
     37 #include "namespace.h"
     38 #include <sys/types.h>
     39 #include <sys/syscall.h>
     40 #include <unistd.h>
     41 
     42 #ifdef __weak_alias
     43 __weak_alias(pread,_sys_pread)
     44 __weak_alias(_pread,_sys_pread)
     45 #endif
     46 #ifdef __lint__
     47 #define _sys_pread pread
     48 #endif
     49 
     50 ssize_t	 _sys_pread(int, void *, size_t, off_t);
     51 
     52 /*
     53  * This function provides 64-bit offset padding that
     54  * is not supplied by GCC 1.X but is supplied by GCC 2.X.
     55  */
     56 ssize_t
     57 _sys_pread(int fd, void *buf, size_t nbyte, off_t offset)
     58 {
     59 	quad_t q;
     60 	int rv;
     61 
     62 	q = __syscall((quad_t)SYS_pread, fd, buf, nbyte, 0, offset);
     63 	if (/* LINTED constant */ sizeof (quad_t) == sizeof (register_t) ||
     64 	    /* LINTED constant */ BYTE_ORDER == LITTLE_ENDIAN)
     65 		rv = (int)q;
     66 	else
     67 		rv = (int)((u_quad_t)q >> 32);
     68 	return rv;
     69 }
     70