NetBSD/usr.sbin/sup/source/filecopy.c

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1993-05-21 18:52:16 +04:00
/*
* Copyright (c) 1991 Carnegie Mellon University
* All Rights Reserved.
*
* 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.
*/
/* filecopy -- copy a file from here to there
*
* Usage: i = filecopy (here,there);
* int i, here, there;
*
* Filecopy performs a fast copy of the file "here" to the
* file "there". Here and there are both file descriptors of
* open files; here is open for input, and there for output.
* Filecopy returns 0 if all is OK; -1 on error.
*
* I have performed some tests for possible improvements to filecopy.
* Using a buffer size of 10240 provides about a 1.5 times speedup
* over 512 for a file of about 200,000 bytes. Of course, other
* buffer sized should also work; this is a rather arbitrary choice.
* I have also tried inserting special startup code to attempt
* to align either the input or the output file to lie on a
* physical (512-byte) block boundary prior to the big loop,
* but this presents only a small (about 5% speedup, so I've
* canned that code. The simple thing seems to be good enough.
*
* HISTORY
* 20-Nov-79 Steven Shafer (sas) at Carnegie-Mellon University
* Rewritten for VAX; same as "filcopy" on PDP-11. Bigger buffer
* size (20 physical blocks) seems to be a big win; aligning things
* on block boundaries seems to be a negligible improvement at
* considerable cost in complexity.
*
*/
#define BUFFERSIZE 10240
int filecopy (here,there)
int here,there;
{
register int kount;
char buffer[BUFFERSIZE];
kount = 0;
while (kount == 0 && (kount=read(here,buffer,BUFFERSIZE)) > 0)
kount -= write (there,buffer,kount);
return (kount ? -1 : 0);
}