prototyping for p{read,write}{,v}

src/include/unistd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: unistd.h,v 1.30 2000/02/19 13:21:25 deraadt Exp $ */
+/*	$OpenBSD: unistd.h,v 1.31 2000/04/20 06:34:18 deraadt Exp $ */
 /*	$NetBSD: unistd.h,v 1.26.4.1 1996/05/28 02:31:51 mrg Exp $	*/
 
 /*-
@@ -112,6 +112,15 @@ ssize_t	 write __P((int, const void *, size_t));
 /* structure timeval required for select() */
 #include <sys/time.h>
 
+/*
+ * X/Open CAE Specification Issue 5 Version 2
+ */
+#if (!defined(_POSIX_C_SOURCE) && !defined(_XOPEN_SOURCE)) || \
+    (_XOPEN_VERSION - 0) >= 500
+ssize_t  pread __P((int, void *, size_t, off_t));
+ssize_t  pwrite __P((int, const void *, size_t, off_t));
+#endif
+
 int	 acct __P((const char *));
 char	*brk __P((const char *));
 int	 chroot __P((const char *));
@@ -165,9 +174,11 @@ int	 rresvport_af __P((int *, int));
 int	 ruserok __P((const char *, int, const char *, const char *));
 int	 quotactl __P((const char *, int, int, char *));
 char	*sbrk __P((int));
-#ifndef _XOPEN_SOURCE
+
+#if !defined(_XOPEN_SOURCE)
 int	 select __P((int, fd_set *, fd_set *, fd_set *, struct timeval *));
 #endif
+
 int	 setdomainname __P((const char *, size_t));
 int	 setegid __P((gid_t));
 int	 seteuid __P((uid_t));