src/Unix/vhd_unix.cpp

/*
 * vhd_unix.cpp -- support for disk images in vhd format 
 *
 *      (C) 2010 Geoffrey Brown
 *
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *
 *      You should have received a copy of the GNU General Public License
 *      along with this program; if not, write to the Free Software
 *      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "sysdeps.h"
#include "vhd_unix.h"
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
extern "C" {
#include <libvhd.h>
}
// libvhd.h defines DEBUG
#undef DEBUG
#define DEBUG 0
#include "debug.h"

void *vhd_unix_open(const char *name, int *size, bool read_only)
{
        int amode = read_only ? R_OK : (R_OK | W_OK);
        int fid;
        vhd_context_t *vhd;

        D(bug("vhd open %s\n", name));

        if (access(name, amode)) {
                D(bug("vhd open -- incorrect permissions %s\n", name));
                return NULL;
        }
  
        if (! (fid = open(name, O_RDONLY))) { 
                D(bug("vhd open -- couldn't open file %s\n", name));
                return NULL;
        } 
        else {
                char buf[9];
                read(fid, buf, sizeof(buf)-1);
                buf[8] = 0;
                close(fid);
                if (strcmp("conectix", buf) != 0) {
                        D(bug("vhd open -- not vhd magic = %s\n", buf));
                        return NULL;
                }
                if (vhd = (vhd_context_t *) malloc(sizeof(vhd_context_t))) {
                        int err;
                        if (err = vhd_open(vhd, name, read_only ? 
                                                                VHD_OPEN_RDONLY : VHD_OPEN_RDWR)) {
                                D(bug("vhd_open failed (%d)\n", err));
                                free(vhd);
                                return NULL;
                        } 
                        else {
                                *size = (int) vhd->footer.curr_size;
                                printf("VHD Open %s\n", name);
                                return (void *) vhd;
                        }
                }
                else {
                        D(bug("vhd open -- malloc failed\n"));
                        return NULL;
                }
        }
}

int vhd_unix_read(void *arg, void *buffer, loff_t offset, size_t length)
{
        vhd_context_t *ctx = (vhd_context_t *) arg;
        int err;
        if ((offset % VHD_SECTOR_SIZE) || (length % VHD_SECTOR_SIZE)) {
                printf("vhd read only supported on sector boundaries (%d)\n",
                                VHD_SECTOR_SIZE);
                return 0;
        }       
        if (err = vhd_io_read(ctx, (char *) buffer, offset / VHD_SECTOR_SIZE, 
                                                        length / VHD_SECTOR_SIZE)){
                D(bug("vhd read error %d\n", err));     
                return err;
        }
        else 
                return length;
}

int vhd_unix_write(void *arg, void *buffer, loff_t offset, size_t length)
{
        int err;
        vhd_context_t *ctx = (vhd_context_t *) arg;

        if ((offset % VHD_SECTOR_SIZE) || (length % VHD_SECTOR_SIZE)) {
                printf("vhd write only supported on sector boundaries (%d)\n",
                                VHD_SECTOR_SIZE);
                return 0;
        }       
        if (err = vhd_io_write(ctx, (char *) buffer, offset/VHD_SECTOR_SIZE,
                                                        length/VHD_SECTOR_SIZE)) {
                D(bug("vhd write error %d\n", err));
                return err;
        }
        else
                return length;
}

void vhd_unix_close(void *arg)
{
        D(bug("vhd close\n"));
        vhd_close((vhd_context_t *) arg);
        free(arg);
}
Revision:	1.1
Committed:	2010-10-19T03:21:52Z (14 years, 1 month ago) by asvitkine
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	[Geoffrey Brown] For my work on digital preservation it's important to have "golden" disk images that are not corrupted by user action. In order to enable this, I've added support for VHD virtual disks (especially snapshots !) to the Linux and OS X versions of BasiliskII and SheepShaver. The support uses the open source libvhd library which is part of xen, available here: http://www.xen.org/products/xen_source.html The piece that's needed is libvhd which is in tools/blktap2 and it can be separately compiled. The vhd-util enables creation of vhd disks and snapshots. Compiling libvhd for OS X is non-trivial and required 1) a new config and 2) a number of small changes to the include files and c files. Compiling for linux is a snap. I use this as follows. 1) create my "golden image" gold.dsk in the usual way 2) create a snapshot: vhd-util snapshot -n gold.vhd -p gold.dsk -m 3) use the snapshot in my prefs file In my work the golden images are in an AFS system which means the golden images can reside at "universal" addresses. The snapshots are initially tiny, so a complete virtual machine configuration -- prefs + snapshot is quick to download for the end user. The snapshots are copy on write which has the pleasant side effect of letting the end user keep any changes.
#	User	Rev	Content
1	asvitkine	1.1	/*
2			* vhd_unix.cpp -- support for disk images in vhd format
3			*
4			* (C) 2010 Geoffrey Brown
5			*
6			* This program is free software; you can redistribute it and/or modify
7			* it under the terms of the GNU General Public License as published by
8			* the Free Software Foundation; either version 2 of the License, or
9			* (at your option) any later version.
10			*
11			* This program is distributed in the hope that it will be useful,
12			* but WITHOUT ANY WARRANTY; without even the implied warranty of
13			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14			* GNU General Public License for more details.
15			*
16			* You should have received a copy of the GNU General Public License
17			* along with this program; if not, write to the Free Software
18			* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19			*/
20
21			#include "sysdeps.h"
22			#include "vhd_unix.h"
23			#include <stdio.h>
24			#include <stdlib.h>
25			#include <unistd.h>
26			#include <string.h>
27			extern "C" {
28			#include <libvhd.h>
29			}
30			// libvhd.h defines DEBUG
31			#undef DEBUG
32			#define DEBUG 0
33			#include "debug.h"
34
35			void vhd_unix_open(const char name, int *size, bool read_only)
36			{
37			int amode = read_only ? R_OK : (R_OK \| W_OK);
38			int fid;
39			vhd_context_t *vhd;
40
41			D(bug("vhd open %s\n", name));
42
43			if (access(name, amode)) {
44			D(bug("vhd open -- incorrect permissions %s\n", name));
45			return NULL;
46			}
47
48			if (! (fid = open(name, O_RDONLY))) {
49			D(bug("vhd open -- couldn't open file %s\n", name));
50			return NULL;
51			}
52			else {
53			char buf[9];
54			read(fid, buf, sizeof(buf)-1);
55			buf[8] = 0;
56			close(fid);
57			if (strcmp("conectix", buf) != 0) {
58			D(bug("vhd open -- not vhd magic = %s\n", buf));
59			return NULL;
60			}
61			if (vhd = (vhd_context_t *) malloc(sizeof(vhd_context_t))) {
62			int err;
63			if (err = vhd_open(vhd, name, read_only ?
64			VHD_OPEN_RDONLY : VHD_OPEN_RDWR)) {
65			D(bug("vhd_open failed (%d)\n", err));
66			free(vhd);
67			return NULL;
68			}
69			else {
70			*size = (int) vhd->footer.curr_size;
71			printf("VHD Open %s\n", name);
72			return (void *) vhd;
73			}
74			}
75			else {
76			D(bug("vhd open -- malloc failed\n"));
77			return NULL;
78			}
79			}
80			}
81
82			int vhd_unix_read(void arg, void buffer, loff_t offset, size_t length)
83			{
84			vhd_context_t ctx = (vhd_context_t ) arg;
85			int err;
86			if ((offset % VHD_SECTOR_SIZE) \|\| (length % VHD_SECTOR_SIZE)) {
87			printf("vhd read only supported on sector boundaries (%d)\n",
88			VHD_SECTOR_SIZE);
89			return 0;
90			}
91			if (err = vhd_io_read(ctx, (char *) buffer, offset / VHD_SECTOR_SIZE,
92			length / VHD_SECTOR_SIZE)){
93			D(bug("vhd read error %d\n", err));
94			return err;
95			}
96			else
97			return length;
98			}
99
100			int vhd_unix_write(void arg, void buffer, loff_t offset, size_t length)
101			{
102			int err;
103			vhd_context_t ctx = (vhd_context_t ) arg;
104
105			if ((offset % VHD_SECTOR_SIZE) \|\| (length % VHD_SECTOR_SIZE)) {
106			printf("vhd write only supported on sector boundaries (%d)\n",
107			VHD_SECTOR_SIZE);
108			return 0;
109			}
110			if (err = vhd_io_write(ctx, (char *) buffer, offset/VHD_SECTOR_SIZE,
111			length/VHD_SECTOR_SIZE)) {
112			D(bug("vhd write error %d\n", err));
113			return err;
114			}
115			else
116			return length;
117			}
118
119			void vhd_unix_close(void *arg)
120			{
121			D(bug("vhd close\n"));
122			vhd_close((vhd_context_t *) arg);
123			free(arg);
124			}