[unix-history] / usr / src / sys / stand / read.c

/*-
* Copyright (c) 1993 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* %sccs.include.redist.c%
*
*      @(#)read.c      7.1 (Berkeley) %G%
*  
*
* Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Author: Alessandro Forin
* 
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
* 
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
* 
* Carnegie Mellon requests users of this software to return to
* 
*  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
*  School of Computer Science
*  Carnegie Mellon University
*  Pittsburgh PA 15213-3890
* 
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/

#include <stand/stand.h>

read(fd, dest, bcount)
       int fd;
       char *dest;
       u_int bcount;
{
       register struct open_file *f = &files[fd];
       u_int resid;

       if ((unsigned)fd >= SOPEN_MAX || !(f->f_flags & F_READ)) {
               errno = EBADF;
               return (-1);
       }
       if (f->f_flags & F_RAW) {
               errno = (f->f_dev->dv_strategy)(f->f_devdata, F_READ,
                       (daddr_t)0, bcount, dest, &resid);
               if (errno)
                       return (-1);
               return (resid);
       }
       resid = bcount;
       if (errno = (f->f_ops->read)(f, dest, bcount, &resid))
               return (-1);
       return (bcount - resid);
}