1:10 p.m.
I finally found time to finish a small project I had left half-baked
in one of my local branches.
Eric Blake (3):
dump: Document --length
dump: Add --offset for further limiting the dump
dump: Add a test of --length and --offset
dump/nbddump.pod | 8 +++++++-
dump/Makefile.am | 2 ++
dump/dump-subset.sh | 48 +++++++++++++++++++++++++++++++++++++++++++++
dump/dump.c | 27 +++++++++++++++++++++----
4 files changed, 80 insertions(+), 5 deletions(-)
create mode 100755 dump/dump-subset.sh
--
2.48.1
1:10 p.m.
New subject: [libnbd PATCH 1/3] dump: Document --length
This option has been present since the introduction of nbddump (commit
c4107b9a, v1.13.4), but was undocumented unless you read further into
the man page. Mentioning it in --help and in the synopsis is useful,
and will set the stage for adding other options that should be
documented.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
dump/nbddump.pod | 2 +-
dump/dump.c | 8 +++++++-
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/dump/nbddump.pod b/dump/nbddump.pod
index 6f1c9b51..b05472fe 100644
--- a/dump/nbddump.pod
+++ b/dump/nbddump.pod
@@ -4,7 +4,7 @@ nbddump - hexdump the content of a disk over NBD
=head1 SYNOPSIS
- nbddump NBD
+ nbddump [-n N|--length N] NBD
C<NBD> is an NBD URI or subprocess:
diff --git a/dump/dump.c b/dump/dump.c
index 71053277..71bedf6a 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -65,7 +65,13 @@ usage (FILE *fp, int exitcode)
"\n"
"Hexdump the content of a disk over NBD:\n"
"\n"
-" nbddump NBD-URI | [ CMD ARGS ... ]\n"
+" nbddump [ OPTIONS ...] NBD-URI | [ CMD ARGS ... ]\n"
+"\n"
+"Options include:\n"
+" --color, --colour Force ANSI color on output to non-terminal\n"
+" --no-color, --no-colour\n"
+" Suppress ANSI color even on output to terminal\n"
+" -n LEN, --length=LEN Truncate output after LEN bytes dumped\n"
"\n"
"Other options:\n"
"\n"
--
2.48.1
1:10 p.m.
New subject: [libnbd PATCH 2/3] dump: Add --offset for further limiting the dump
We already have --length (aka --limit) for limiting how far the dump
goes; the obvious counterpart is --offset (aka --skip) for controlling
where to start the dump.
I did not bother to try and print an unaligned partial first line so
that subsequent lines can be nicely aligned, but rather the dump
always starts with a full line even when it displays with unusual
offsets.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
dump/nbddump.pod | 8 +++++++-
dump/dump.c | 19 ++++++++++++++++---
2 files changed, 23 insertions(+), 4 deletions(-)
diff --git a/dump/nbddump.pod b/dump/nbddump.pod
index b05472fe..6acac426 100644
--- a/dump/nbddump.pod
+++ b/dump/nbddump.pod
@@ -4,7 +4,7 @@ nbddump - hexdump the content of a disk over NBD
=head1 SYNOPSIS
- nbddump [-n N|--length N] NBD
+ nbddump [-n N|--length N] [-o N|--offset N] NBD
C<NBD> is an NBD URI or subprocess:
@@ -103,6 +103,12 @@ if the output seems to be a terminal, and disable them if not.
Dump up to I<N> bytes and then stop.
+=item B<--offset=>N
+
+=item B<-o> N
+
+Start the dump at offset I<N> bytes.
+
=item B<-V>
=item B<--version>
diff --git a/dump/dump.c b/dump/dump.c
index 71bedf6a..7a475196 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -44,6 +44,7 @@ static const char *progname;
static struct nbd_handle *nbd;
bool colour;
static uint64_t limit = UINT64_MAX; /* --length (unlimited by default) */
+static uint64_t skip; /* --offset (0 by default) */
static int64_t size; /* actual size */
static bool can_meta_context; /* did we get extent data? */
@@ -72,6 +73,7 @@ usage (FILE *fp, int exitcode)
" --no-color, --no-colour\n"
" Suppress ANSI color even on output to terminal\n"
" -n LEN, --length=LEN Truncate output after LEN bytes dumped\n"
+" -o OFF, --offset=OFF Skip to offset OFF bytes before dumping\n"
"\n"
"Other options:\n"
"\n"
@@ -99,7 +101,7 @@ main (int argc, char *argv[])
COLOUR_OPTION,
NO_COLOUR_OPTION,
};
- const char *short_options = "n:V";
+ const char *short_options = "n:o:V";
const struct option long_options[] = {
{ "help", no_argument, NULL, HELP_OPTION },
{ "long-options", no_argument, NULL, LONG_OPTIONS },
@@ -116,6 +118,8 @@ main (int argc, char *argv[])
{ "no-colours", no_argument, NULL, NO_COLOUR_OPTION },
{ "length", required_argument, NULL, 'n' },
{ "limit", required_argument, NULL, 'n' },
+ { "offset", required_argument, NULL, 'o' },
+ { "skip", required_argument, NULL, 'o' },
{ NULL }
};
int c;
@@ -165,6 +169,15 @@ main (int argc, char *argv[])
}
break;
+ case 'o':
+ /* XXX Allow human sizes here. */
+ if (sscanf (optarg, "%" SCNu64, &skip) != 1) {
+ fprintf (stderr, "%s: could not parse --offset option: %s\n",
+ progname, optarg);
+ exit (EXIT_FAILURE);
+ }
+ break;
+
case 'V':
display_version ("nbddump");
exit (EXIT_SUCCESS);
@@ -342,8 +355,8 @@ do_dump (void)
const char *splat = colour ? "☆" : "*";
const char *pipe = colour ? "│" : "|";
const char *dot = colour ? "·" : ".";
- uint64_t offset = 0;
- uint64_t count = size > limit ? limit : size;
+ uint64_t offset = skip;
+ uint64_t count = size - offset > limit ? limit : size - offset;
size_t i, j;
char last[16];
bool printed_splat = false, same;
--
2.48.1
1:10 p.m.
New subject: [libnbd PATCH 3/3] dump: Add a test of --length and --offset
Prove that our subset-limiting options work.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
dump/Makefile.am | 2 ++
dump/dump-subset.sh | 48 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
create mode 100755 dump/dump-subset.sh
diff --git a/dump/Makefile.am b/dump/Makefile.am
index 734f149b..335ff8db 100644
--- a/dump/Makefile.am
+++ b/dump/Makefile.am
@@ -21,6 +21,7 @@ EXTRA_DIST = \
dump-data.sh \
dump-empty-qcow2.sh \
dump-pattern.sh \
+ dump-subset.sh \
nbddump.pod \
test-long-options.sh \
test-short-options.sh \
@@ -70,6 +71,7 @@ TESTS = \
dump-data.sh \
dump-empty-qcow2.sh \
dump-pattern.sh \
+ dump-subset.sh \
test-long-options.sh \
test-short-options.sh \
test-version.sh \
diff --git a/dump/dump-subset.sh b/dump/dump-subset.sh
new file mode 100755
index 00000000..42444ae1
--- /dev/null
+++ b/dump/dump-subset.sh
@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# nbd client library in userspace
+# Copyright Red Hat
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+. ../tests/functions.sh
+
+set -e
+set -x
+
+requires $NBDKIT --version
+requires $NBDKIT pattern --dump-plugin
+requires $NBDKIT -U - null --run 'test "$uri" != ""'
+requires nbdsh -c 'exit(not h.supports_uri())'
+
+output=dump-subset.out
+rm -f $output
+cleanup_fn rm -f $output
+
+$NBDKIT -U - pattern size=100 --run 'nbddump --offset=15 --length=33
"$uri"' > $output
+
+# Repeat with alternate spellings
+$NBDKIT -U - pattern size=100 --run 'nbddump --skip 15 --limit 33
"$uri"' >> $output
+
+cat $output
+
+if [ "$(cat $output)" != '000000000f: 08 00 00 00 00 00 00 00 10 00 00 00
00 00 00 00 |................|
+000000001f: 18 00 00 00 00 00 00 00 20 00 00 00 00 00 00 00 |........ .......|
+000000002f: 28 |( |
+000000000f: 08 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00 |................|
+000000001f: 18 00 00 00 00 00 00 00 20 00 00 00 00 00 00 00 |........ .......|
+000000002f: 28 |( |' ];
then
+ echo "$0: unexpected output from nbddump command"
+ exit 1
+fi
--
2.48.1
2:56 a.m.
New subject: [libnbd PATCH 3/3] dump: Add a test of --length and --offset
ACK series
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top
10:32 a.m.
New subject: [libnbd PATCH 3/3] dump: Add a test of --length and --offset
On Wed, Feb 05, 2025 at 08:56:15AM +0000, Richard W.M. Jones wrote:
ACK series
Now upstream as f61a7446..a33e7a93
--
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization: qemu.org | libguestfs.org
28
days inactive
30
days old
5 comments
2 participants
participants (2)
-
Eric Blake -
Richard W.M. Jones