1/* ----------------------------------------------------------------------- *
2 *
3 *   Copyright 2004-2008 H. Peter Anvin - All Rights Reserved
4 *
5 *   Permission is hereby granted, free of charge, to any person
6 *   obtaining a copy of this software and associated documentation
7 *   files (the "Software"), to deal in the Software without
8 *   restriction, including without limitation the rights to use,
9 *   copy, modify, merge, publish, distribute, sublicense, and/or
10 *   sell copies of the Software, and to permit persons to whom
11 *   the Software is furnished to do so, subject to the following
12 *   conditions:
13 *
14 *   The above copyright notice and this permission notice shall
15 *   be included in all copies or substantial portions of the Software.
16 *
17 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
19 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
21 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
22 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
23 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
24 *   OTHER DEALINGS IN THE SOFTWARE.
25 *
26 * ----------------------------------------------------------------------- */
27
28/*
29 * read.c
30 *
31 * Reading from a file
32 */
33
34#include <errno.h>
35#include <string.h>
36#include <com32.h>
37#include <pmapi.h>
38#include <syslinux/pmapi.h>
39#include <minmax.h>
40#include "file.h"
41
42int __file_get_block(struct file_info *fp)
43{
44    ssize_t bytes_read;
45
46    bytes_read = pmapi_read_file(&fp->i.fd.handle, fp->i.buf,
47					  MAXBLOCK >> fp->i.fd.blocklg2);
48    if (!bytes_read) {
49	errno = EIO;
50	return -1;
51    }
52
53    fp->i.nbytes = bytes_read;
54    fp->i.datap  = fp->i.buf;
55    return 0;
56}
57
58ssize_t __file_read(struct file_info * fp, void *buf, size_t count)
59{
60    char *bufp = buf;
61    ssize_t n = 0;
62    size_t ncopy;
63
64    while (count) {
65	if (fp->i.nbytes == 0) {
66	    if (fp->i.offset >= fp->i.fd.size || !fp->i.fd.handle)
67		return n;	/* As good as it gets... */
68
69	    if (count > MAXBLOCK) {
70		/* Large transfer: copy directly, without buffering */
71		ncopy = pmapi_read_file(&fp->i.fd.handle, bufp,
72						 count >> fp->i.fd.blocklg2);
73		if (!ncopy) {
74		    errno = EIO;
75		    return n ? n : -1;
76		}
77
78		goto got_data;
79	    } else {
80		if (__file_get_block(fp))
81		    return n ? n : -1;
82	    }
83	}
84
85	ncopy = min(count, fp->i.nbytes);
86	memcpy(bufp, fp->i.datap, ncopy);
87
88	fp->i.datap += ncopy;
89	fp->i.offset += ncopy;
90	fp->i.nbytes -= ncopy;
91
92    got_data:
93	n += ncopy;
94	bufp += ncopy;
95	count -= ncopy;
96    }
97
98    return n;
99}
100