usr.sbin/sup/source/filecopy.c

   1 /*      $NetBSD: filecopy.c,v 1.4 2002/07/10 20:19:39 wiz Exp $ */
   2
   3 /*
   4  * Copyright (c) 1991 Carnegie Mellon University
   5  * All Rights Reserved.
   6  *
   7  * Permission to use, copy, modify and distribute this software and its
   8  * documentation is hereby granted, provided that both the copyright
   9  * notice and this permission notice appear in all copies of the
  10  * software, derivative works or modified versions, and any portions
  11  * thereof, and that both notices appear in supporting documentation.
  12  *
  13  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  14  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  15  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  16  *
  17  * Carnegie Mellon requests users of this software to return to
  18  *
  19  *  Software Distribution Coordinator   or   Software.Distribution@CS.CMU.EDU
  20  *  School of Computer Science
  21  *  Carnegie Mellon University
  22  *  Pittsburgh PA 15213-3890
  23  *
  24  * any improvements or extensions that they make and grant Carnegie the rights
  25  * to redistribute these changes.
  26  */
  27 /*  filecopy  --  copy a file from here to there
  28  *
  29  *  Usage:  i = filecopy (here,there);
  30  *      int i, here, there;
  31  *
  32  *  Filecopy performs a fast copy of the file "here" to the
  33  *  file "there".  Here and there are both file descriptors of
  34  *  open files; here is open for input, and there for output.
  35  *  Filecopy returns 0 if all is OK; -1 on error.
  36  *
  37  *  I have performed some tests for possible improvements to filecopy.
  38  *  Using a buffer size of 10240 provides about a 1.5 times speedup
  39  *  over 512 for a file of about 200,000 bytes.  Of course, other
  40  *  buffer sized should also work; this is a rather arbitrary choice.
  41  *  I have also tried inserting special startup code to attempt
  42  *  to align either the input or the output file to lie on a
  43  *  physical (512-byte) block boundary prior to the big loop,
  44  *  but this presents only a small (about 5% speedup, so I've
  45  *  canned that code.  The simple thing seems to be good enough.
  46  *
  47  *  HISTORY
  48  * 20-Nov-79  Steven Shafer (sas) at Carnegie-Mellon University
  49  *      Rewritten for VAX; same as "filcopy" on PDP-11.  Bigger buffer
  50  *      size (20 physical blocks) seems to be a big win; aligning things
  51  *      on block boundaries seems to be a negligible improvement at
  52  *      considerable cost in complexity.
  53  *
  54  */
  55
  56 #define BUFFERSIZE 10240
  57 #include "supcdefs.h"
  58 #include "supextern.h"
  59
  60 ssize_t
  61 filecopy(int here, int there)
  62 {
  63         ssize_t kount;
  64         char buffer[BUFFERSIZE];
  65         kount = 0;
  66         while (kount == 0 && (kount = read(here, buffer, BUFFERSIZE)) > 0)
  67                 kount -= write(there, buffer, (size_t)kount);
  68         return (kount ? -1 : 0);
  69 }