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/* libguestfs - the guestfsd daemon
* Copyright (C) 2009-2011 Red Hat Inc.
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include "daemon.h"
#include "actions.h"
/* Return true iff the buffer is all zero bytes.
*
* Note that gcc is smart enough to optimize this properly:
* http://stackoverflow.com/questions/1493936/faster-means-of-checking-for-an-empty-buffer-in-c/1493989#1493989
*/
static int
is_zero (const char *buffer, size_t size)
{
size_t i;
for (i = 0; i < size; ++i) {
if (buffer[i] != 0)
return 0;
}
return 1;
}
static const char zero_buf[4096];
int
do_zero (const char *device)
{
char buf[sizeof zero_buf];
int fd;
size_t i, offset;
fd = open (device, O_RDWR);
if (fd == -1) {
reply_with_perror ("%s", device);
return -1;
}
for (i = 0; i < 32; ++i) {
offset = i * sizeof zero_buf;
/* Check if the block is already zero before overwriting it. */
if (pread (fd, buf, sizeof buf, offset) != sizeof buf) {
reply_with_perror ("pread: %s", device);
close (fd);
return -1;
}
if (!is_zero (buf, sizeof buf)) {
if (pwrite (fd, zero_buf, sizeof zero_buf, offset) != sizeof zero_buf) {
reply_with_perror ("pwrite: %s", device);
close (fd);
return -1;
}
}
notify_progress ((uint64_t) i, 32);
}
if (close (fd) == -1) {
reply_with_perror ("close: %s", device);
return -1;
}
return 0;
}
int
do_zero_device (const char *device)
{
int64_t ssize = do_blockdev_getsize64 (device);
if (ssize == -1)
return -1;
uint64_t size = (uint64_t) ssize;
int fd = open (device, O_RDWR);
if (fd == -1) {
reply_with_perror ("%s", device);
return -1;
}
char buf[sizeof zero_buf];
uint64_t pos = 0;
while (pos < size) {
uint64_t n64 = size - pos;
size_t n;
if (n64 > sizeof buf)
n = sizeof buf;
else
n = (size_t) n64; /* safe because of if condition */
/* Check if the block is already zero before overwriting it. */
ssize_t r;
r = pread (fd, buf, n, pos);
if (r == -1) {
reply_with_perror ("pread: %s at offset %" PRIu64, device, pos);
close (fd);
return -1;
}
if (!is_zero (buf, sizeof buf)) {
r = pwrite (fd, zero_buf, n, pos);
if (r == -1) {
reply_with_perror ("pwrite: %s (with %" PRId64 " bytes left to write)",
device, size);
close (fd);
return -1;
}
pos += r;
}
else
pos += n;
notify_progress (pos, size);
}
if (close (fd) == -1) {
reply_with_perror ("close: %s", device);
return -1;
}
return 0;
}
int
do_is_zero (const char *path)
{
int fd;
char buf[1024*1024];
ssize_t r;
CHROOT_IN;
fd = open (path, O_RDONLY);
CHROOT_OUT;
if (fd == -1) {
reply_with_perror ("open: %s", path);
return -1;
}
while ((r = read (fd, buf, sizeof buf)) > 0) {
if (!is_zero (buf, r)) {
close (fd);
return 0;
}
}
if (r == -1) {
reply_with_perror ("read: %s", path);
close (fd);
return -1;
}
if (close (fd) == -1) {
reply_with_perror ("close: %s", path);
return -1;
}
return 1;
}
int
do_is_zero_device (const char *device)
{
int fd;
char buf[1024*1024];
ssize_t r;
fd = open (device, O_RDONLY);
if (fd == -1) {
reply_with_perror ("open: %s", device);
return -1;
}
while ((r = read (fd, buf, sizeof buf)) > 0) {
if (!is_zero (buf, r)) {
close (fd);
return 0;
}
}
if (r == -1) {
reply_with_perror ("read: %s", device);
close (fd);
return -1;
}
if (close (fd) == -1) {
reply_with_perror ("close: %s", device);
return -1;
}
return 1;
}
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