1 /* Copyright 2021 Alain Knaff.
2 * This file is part of mtools.
3 *
4 * Mtools is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
8 *
9 * Mtools is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with Mtools. If not, see <http://www.gnu.org/licenses/>.
16 *
17 * filter to support filesystems stored at an offset into their image
18 */
19
20 #include "sysincludes.h"
21 #include "msdos.h"
22 #include "mtools.h"
23 #include "offset.h"
24
25 typedef struct Offset_t {
26 struct Stream_t head;
27
28 mt_off_t offset;
29 } Offset_t;
30
offset_pread(Stream_t * Stream,char * buf,mt_off_t start,size_t len)31 static ssize_t offset_pread(Stream_t *Stream, char *buf,
32 mt_off_t start, size_t len)
33 {
34 DeclareThis(Offset_t);
35 return PREADS(This->head.Next, buf, start+This->offset, len);
36 }
37
offset_pwrite(Stream_t * Stream,char * buf,mt_off_t start,size_t len)38 static ssize_t offset_pwrite(Stream_t *Stream, char *buf,
39 mt_off_t start, size_t len)
40 {
41 DeclareThis(Offset_t);
42 return PWRITES(This->head.Next, buf, start+This->offset, len);
43 }
44
45 static Class_t OffsetClass = {
46 0,
47 0,
48 offset_pread,
49 offset_pwrite,
50 0, /* flush */
51 0, /* free */
52 set_geom_pass_through, /* set_geom */
53 0, /* get_data */
54 0, /* pre-allocate */
55 get_dosConvert_pass_through, /* dos convert */
56 0, /* discard */
57 };
58
OpenOffset(Stream_t * Next,struct device * dev,off_t offset,char * errmsg,mt_off_t * maxSize)59 Stream_t *OpenOffset(Stream_t *Next, struct device *dev, off_t offset,
60 char *errmsg, mt_off_t *maxSize) {
61 Offset_t *This;
62
63 This = New(Offset_t);
64 if (!This){
65 printOom();
66 return 0;
67 }
68 memset((void*)This, 0, sizeof(Offset_t));
69 init_head(&This->head, &OffsetClass, Next);
70
71 This->offset = offset;
72
73 if(maxSize) {
74 if(This->offset > *maxSize) {
75 if(errmsg)
76 sprintf(errmsg,"init: Big disks not supported");
77 goto exit_0;
78 }
79
80 *maxSize -= This->offset;
81 }
82
83 if(adjust_tot_sectors(dev, This->offset, errmsg) < 0)
84 goto exit_0;
85
86 return &This->head;
87 exit_0:
88 Free(This);
89 return NULL;
90 }
91