pread.c revision 1.8 
1/*	$NetBSD: pread.c,v 1.8 2019/09/13 02:19:46 manu Exp $	 */
2
3/*
4 * Copyright (c) 1996
5 *	Matthias Drochner.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29/* read into destination in flat addr space */
30
31#include <lib/libsa/stand.h>
32
33#include "libi386.h"
34
35#ifdef SAVE_MEMORY
36#define BUFSIZE (1*1024)
37#else
38#define BUFSIZE (4*1024)
39#endif
40
41static char     *buf;
42
43ssize_t
44pread(int fd, void *dest, size_t size)
45{
46	size_t             rsize;
47
48	if (!buf)
49		buf = alloc(BUFSIZE);
50
51	rsize = size;
52	while (rsize > 0) {
53		size_t count;
54		ssize_t got;
55
56		count = (rsize < BUFSIZE ? rsize : BUFSIZE);
57
58		got = read(fd, buf, count);
59		if (got < 0)
60			return -1;
61
62		/* put to physical space */
63		vpbcopy(buf, dest, got);
64
65		dest += got;
66		rsize -= got;
67		if (got < count)
68			break;	/* EOF */
69	}
70	return size - rsize;
71}
72