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read.c revision 1.1 
      1 /*-
      2  * Copyright (c) 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * The Mach Operating System project at Carnegie-Mellon University.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  *
     36  *	from: @(#)read.c	8.1 (Berkeley) 6/11/93
     37  *
     38  *
     39  * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
     40  * All Rights Reserved.
     41  *
     42  * Author: Alessandro Forin
     43  *
     44  * Permission to use, copy, modify and distribute this software and its
     45  * documentation is hereby granted, provided that both the copyright
     46  * notice and this permission notice appear in all copies of the
     47  * software, derivative works or modified versions, and any portions
     48  * thereof, and that both notices appear in supporting documentation.
     49  *
     50  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     51  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
     52  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     53  *
     54  * Carnegie Mellon requests users of this software to return to
     55  *
     56  *  Software Distribution Coordinator  or  Software.Distribution (at) CS.CMU.EDU
     57  *  School of Computer Science
     58  *  Carnegie Mellon University
     59  *  Pittsburgh PA 15213-3890
     60  *
     61  * any improvements or extensions that they make and grant Carnegie the
     62  * rights to redistribute these changes.
     63  *
     64  *	$Id: read.c,v 1.1 1994/01/26 02:03:54 brezak Exp $
     65  */
     66 
     67 #include "stand.h"
     68 
     69 read(fd, dest, bcount)
     70 	int fd;
     71 	char *dest;
     72 	u_int bcount;
     73 {
     74 	register struct open_file *f = &files[fd];
     75 	u_int resid;
     76 
     77 	if ((unsigned)fd >= SOPEN_MAX || !(f->f_flags & F_READ)) {
     78 		errno = EBADF;
     79 		return (-1);
     80 	}
     81 	if (f->f_flags & F_RAW) {
     82 		errno = (f->f_dev->dv_strategy)(f->f_devdata, F_READ,
     83 			(daddr_t)0, bcount, dest, &resid);
     84 		if (errno)
     85 			return (-1);
     86 		return (resid);
     87 	}
     88 	resid = bcount;
     89 	if (errno = (f->f_ops->read)(f, dest, bcount, &resid))
     90 		return (-1);
     91 	return (bcount - resid);
     92 }
     93