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qemu-img: add skip option to dd

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This adds the skip option which allows qemu-img dd to skip a number of blocks
before copying the input.

A test case was added to test the skip option.

Signed-off-by: Reda Sallahi <fullmanet@gmail.com>
Message-id: 20160810141609.32727-1-fullmanet@gmail.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Reda Sallahi 2016-08-10 16:16:09 +02:00 • committed by Max Reitz
parent 86ce1f6e2b
commit f7c1553388
6 changed files with 174 additions and 8 deletions
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50
qemu-img.c
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@ -173,7 +173,8 @@ static void QEMU_NORETURN help(void)
"(default: 512)\n"
" 'count=N' copy only N input blocks\n"
" 'if=FILE' read from FILE\n"
" 'of=FILE' write to FILE\n";
" 'of=FILE' write to FILE\n"
" 'skip=N' skip N bs-sized blocks at the start of input\n";
printf("%s\nSupported formats:", help_msg);
bdrv_iterate_format(format_print, NULL);
@ -3807,6 +3808,7 @@ out:
#define C_COUNT 02
#define C_IF 04
#define C_OF 010
#define C_SKIP 020
struct DdInfo {
unsigned int flags;
@ -3817,6 +3819,7 @@ struct DdIo {
int bsz; /* Block size */
char *filename;
uint8_t *buf;
int64_t offset;
};
struct DdOpts {
@ -3877,6 +3880,22 @@ static int img_dd_of(const char *arg,
return 0;
}
static int img_dd_skip(const char *arg,
struct DdIo *in, struct DdIo *out,
struct DdInfo *dd)
{
char *end;
in->offset = qemu_strtosz_suffix(arg, &end, QEMU_STRTOSZ_DEFSUFFIX_B);
if (in->offset < 0 || *end) {
error_report("invalid number: '%s'", arg);
return 1;
}
return 0;
}
static int img_dd(int argc, char **argv)
{
int ret = 0;
@ -3900,12 +3919,14 @@ static int img_dd(int argc, char **argv)
struct DdIo in = {
.bsz = 512, /* Block size is by default 512 bytes */
.filename = NULL,
.buf = NULL
.buf = NULL,
.offset = 0
};
struct DdIo out = {
.bsz = 512,
.filename = NULL,
.buf = NULL
.buf = NULL,
.offset = 0
};
const struct DdOpts options[] = {
@ -3913,6 +3934,7 @@ static int img_dd(int argc, char **argv)
{ "count", img_dd_count, C_COUNT },
{ "if", img_dd_if, C_IF },
{ "of", img_dd_of, C_OF },
{ "skip", img_dd_skip, C_SKIP },
{ NULL, NULL, 0 }
};
const struct option long_options[] = {
@ -4032,7 +4054,14 @@ static int img_dd(int argc, char **argv)
size = dd.count * in.bsz;
}
qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
/* Overflow means the specified offset is beyond input image's size */
if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
size < in.bsz * in.offset)) {
qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort);
} else {
qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
size - in.bsz * in.offset, &error_abort);
}
ret = bdrv_create(drv, out.filename, opts, &local_err);
if (ret < 0) {
@ -4051,9 +4080,20 @@ static int img_dd(int argc, char **argv)
goto out;
}
if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
size < in.offset * in.bsz)) {
/* We give a warning if the skip option is bigger than the input
* size and create an empty output disk image (i.e. like dd(1)).
*/
error_report("%s: cannot skip to specified offset", in.filename);
in_pos = size;
} else {
in_pos = in.offset * in.bsz;
}
in.buf = g_new(uint8_t, in.bsz);
for (in_pos = 0, out_pos = 0; in_pos < size; block_count++) {
for (out_pos = 0; in_pos < size; block_count++) {
int in_ret, out_ret;
if (in_pos + in.bsz > size) {