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
__file_get_block(struct file_info * fp)42 int __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
__file_read(struct file_info * fp,void * buf,size_t count)58 ssize_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