[Libguestfs] [PATCH nbdkit] New filter: gzip
Richard W.M. Jones
rjones at redhat.com
Fri Jul 10 11:50:55 UTC 2020
Turn the existing nbdkit-gzip-plugin into a filter so it can be
applied on top of files or other sources:
nbdkit file --filter=gzip file.gz
nbdkit curl --filter=gzip https://example.com/disk.gz
Because of the nature of the gzip format which is not blocked based
and thus not seekable, this filter caches the whole uncompressed file
in a hidden temporary file. This is required in order to implement
.get_size. See this link for a more detailed explanation:
https://stackoverflow.com/a/9213826
This commit deprecates nbdkit-gzip-plugin and suggests removal in
nbdkit 1.26.
---
filters/gzip/nbdkit-gzip-filter.pod | 85 +++++++
filters/tar/nbdkit-tar-filter.pod | 7 +-
plugins/gzip/nbdkit-gzip-plugin.pod | 9 +
configure.ac | 10 +-
filters/gzip/Makefile.am | 75 ++++++
tests/Makefile.am | 34 +--
filters/gzip/gzip.c | 347 ++++++++++++++++++++++++++++
tests/test-gzip.c | 4 +-
TODO | 2 -
9 files changed, 547 insertions(+), 26 deletions(-)
diff --git a/filters/gzip/nbdkit-gzip-filter.pod b/filters/gzip/nbdkit-gzip-filter.pod
new file mode 100644
index 00000000..da0cf626
--- /dev/null
+++ b/filters/gzip/nbdkit-gzip-filter.pod
@@ -0,0 +1,85 @@
+=head1 NAME
+
+nbdkit-gzip-filter - decompress a .gz file
+
+=head1 SYNOPSIS
+
+ nbdkit file --filter=gzip FILENAME.gz
+
+=head1 DESCRIPTION
+
+C<nbdkit-gzip-filter> is a filter for L<nbdkit(1)> which transparently
+decompresses a gzip-compressed file. You can place this filter on top
+of L<nbdkit-file-plugin(1)> to decompress a local F<.gz> file, or on
+top of other plugins such as L<nbdkit-curl-plugin(1)>:
+
+ nbdkit curl --filter=gzip https://example.com/disk.gz
+
+With L<nbdkit-tar-filter(1)> it can be used to extract files from a
+compressed tar file:
+
+ nbdkit curl --filter=tar --filter=gzip \
+ https://example.com/file.tar.gz tar-entry=disk.img
+
+The filter only allows read-only connections.
+
+B<Note> that gzip files are not very good for random access in large
+files because seeking to a position in the gzip file involves
+decompressing all data before that point in the file. A more
+practical method to compress large disk images is to use the L<xz(1)>
+format and L<nbdkit-xz-filter(1)>.
+
+To allow seeking this filter has to keep the contents of the complete
+uncompressed file, which it does in a hidden temporary file under
+C<$TMPDIR>.
+
+=head1 PARAMETERS
+
+There are no parameters specific to this plugin.
+
+=head1 ENVIRONMENT VARIABLES
+
+=over 4
+
+=item C<TMPDIR>
+
+Because the gzip format is not seekable, this filter has to store the
+complete contents of the compressed file in a temporary file located
+in F</var/tmp> by default. You can override this location by setting
+the C<TMPDIR> environment variable before starting nbdkit.
+
+=back
+
+=head1 FILES
+
+=over 4
+
+=item F<$plugindir/nbdkit-gzip-plugin.so>
+
+The plugin.
+
+Use C<nbdkit --dump-config> to find the location of C<$plugindir>.
+
+=back
+
+=head1 VERSION
+
+C<nbdkit-gzip-filter> first appeared in nbdkit 1.22. It is derived
+from C<nbdkit-gzip-plugin> which first appeared in nbdkit 1.0.
+
+=head1 SEE ALSO
+
+L<nbdkit-curl-plugin(1)>,
+L<nbdkit-file-plugin(1)>,
+L<nbdkit-tar-filter(1)>,
+L<nbdkit-xz-filter(1)>,
+L<nbdkit(1)>,
+L<nbdkit-plugin(3)>.
+
+=head1 AUTHORS
+
+Richard W.M. Jones
+
+=head1 COPYRIGHT
+
+Copyright (C) 2013-2020 Red Hat Inc.
diff --git a/filters/tar/nbdkit-tar-filter.pod b/filters/tar/nbdkit-tar-filter.pod
index 56d4cab1..0f0734c3 100644
--- a/filters/tar/nbdkit-tar-filter.pod
+++ b/filters/tar/nbdkit-tar-filter.pod
@@ -42,11 +42,13 @@ server use:
nbdkit -r curl https://example.com/file.tar \
--filter=tar tar-entry=disk.img
-=head2 Open an xz-compressed tar file (read-only)
+=head2 Open an gzip-compressed tar file (read-only)
This filter cannot handle compressed tar files itself, but you can
-combine it with L<nbdkit-xz-filter(1)>:
+combine it with L<nbdkit-gzip-filter(1)> or L<nbdkit-xz-filter(1)>:
+ nbdkit file filename.tar.gz \
+ --filter=tar tar-entry=disk.img --filter=gzip
nbdkit file filename.tar.xz \
--filter=tar tar-entry=disk.img --filter=xz
@@ -100,6 +102,7 @@ from C<nbdkit-tar-plugin> which first appeared in nbdkit 1.2.
L<nbdkit(1)>,
L<nbdkit-curl-plugin(1)>,
L<nbdkit-file-plugin(1)>,
+L<nbdkit-gzip-filter(1)>,
L<nbdkit-offset-filter(1)>,
L<nbdkit-plugin(3)>,
L<nbdkit-ssh-plugin(1)>,
diff --git a/plugins/gzip/nbdkit-gzip-plugin.pod b/plugins/gzip/nbdkit-gzip-plugin.pod
index 1b090125..4cd91ede 100644
--- a/plugins/gzip/nbdkit-gzip-plugin.pod
+++ b/plugins/gzip/nbdkit-gzip-plugin.pod
@@ -6,6 +6,15 @@ nbdkit-gzip-plugin - nbdkit gzip plugin
nbdkit gzip [file=]FILENAME.gz
+=head1 DEPRECATED
+
+B<The gzip plugin is deprecated in S<nbdkit E<ge> 1.22.17> and will be
+removed in S<nbdkit 1.26>>. It has been replaced with a filter with
+the same functionality, see L<nbdkit-gzip-filter(1)>. You can use the
+filter like this:
+
+ nbdkit file --filter=gzip FILENAME.gz
+
=head1 DESCRIPTION
C<nbdkit-gzip-plugin> is a file serving plugin for L<nbdkit(1)>.
diff --git a/configure.ac b/configure.ac
index b51b67b6..3c1f2e11 100644
--- a/configure.ac
+++ b/configure.ac
@@ -105,6 +105,7 @@ filters="\
ext2 \
extentlist \
fua \
+ gzip \
ip \
limit \
log \
@@ -899,10 +900,10 @@ AS_IF([test "$with_libvirt" != "no"],[
])
AM_CONDITIONAL([HAVE_LIBVIRT],[test "x$LIBVIRT_LIBS" != "x"])
-dnl Check for zlib (only if you want to compile the gzip plugin).
+dnl Check for zlib (only if you want to compile the gzip filter).
AC_ARG_WITH([zlib],
[AS_HELP_STRING([--without-zlib],
- [disable gzip plugin @<:@default=check@:>@])],
+ [disable gzip filter @<:@default=check@:>@])],
[],
[with_zlib=check])
AS_IF([test "$with_zlib" != "no"],[
@@ -911,7 +912,7 @@ AS_IF([test "$with_zlib" != "no"],[
AC_SUBST([ZLIB_LIBS])
AC_DEFINE([HAVE_ZLIB],[1],[zlib found at compile time.])
],
- [AC_MSG_WARN([zlib >= 1.2.3.5 not found, gzip plugin will be disabled])])
+ [AC_MSG_WARN([zlib >= 1.2.3.5 not found, gzip filter will be disabled])])
])
AM_CONDITIONAL([HAVE_ZLIB],[test "x$ZLIB_LIBS" != "x"])
@@ -1144,6 +1145,7 @@ AC_CONFIG_FILES([Makefile
filters/ext2/Makefile
filters/extentlist/Makefile
filters/fua/Makefile
+ filters/gzip/Makefile
filters/ip/Makefile
filters/limit/Makefile
filters/log/Makefile
@@ -1253,6 +1255,8 @@ echo "Optional filters:"
echo
feature "ext2 ................................... " \
test "x$HAVE_EXT2_TRUE" = "x"
+feature "gzip ................................... " \
+ test "x$HAVE_ZLIB_TRUE" = "x"
feature "xz ..................................... " \
test "x$HAVE_LIBLZMA_TRUE" = "x"
diff --git a/filters/gzip/Makefile.am b/filters/gzip/Makefile.am
new file mode 100644
index 00000000..a329fab8
--- /dev/null
+++ b/filters/gzip/Makefile.am
@@ -0,0 +1,75 @@
+# nbdkit
+# Copyright (C) 2019-2020 Red Hat Inc.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+include $(top_srcdir)/common-rules.mk
+
+EXTRA_DIST = nbdkit-gzip-filter.pod
+
+if HAVE_ZLIB
+
+filter_LTLIBRARIES = nbdkit-gzip-filter.la
+
+nbdkit_gzip_filter_la_SOURCES = \
+ gzip.c \
+ $(top_srcdir)/include/nbdkit-filter.h \
+ $(NULL)
+
+nbdkit_gzip_filter_la_CPPFLAGS = \
+ -I$(top_srcdir)/include \
+ -I$(top_srcdir)/common/include \
+ -I$(top_srcdir)/common/utils \
+ $(NULL)
+nbdkit_gzip_filter_la_CFLAGS = \
+ $(WARNINGS_CFLAGS) \
+ $(ZLIB_CFLAGS) \
+ $(NULL)
+nbdkit_gzip_filter_la_LIBADD = \
+ $(top_builddir)/common/utils/libutils.la \
+ $(ZLIB_LIBS) \
+ $(NULL)
+nbdkit_gzip_filter_la_LDFLAGS = \
+ -module -avoid-version -shared $(SHARED_LDFLAGS) \
+ -Wl,--version-script=$(top_srcdir)/filters/filters.syms \
+ $(NULL)
+
+if HAVE_POD
+
+man_MANS = nbdkit-gzip-filter.1
+CLEANFILES += $(man_MANS)
+
+nbdkit-gzip-filter.1: nbdkit-gzip-filter.pod
+ $(PODWRAPPER) --section=1 --man $@ \
+ --html $(top_builddir)/html/$@.html \
+ $<
+
+endif HAVE_POD
+
+endif
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 2b5737b8..77f21d79 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -557,23 +557,6 @@ EXTRA_DIST += test-floppy.sh
TESTS += test-full.sh
EXTRA_DIST += test-full.sh
-# gzip plugin test.
-if HAVE_MKE2FS_WITH_D
-if HAVE_ZLIB
-LIBGUESTFS_TESTS += test-gzip
-check_DATA += disk.gz
-CLEANFILES += disk.gz
-
-test_gzip_SOURCES = test-gzip.c test.h
-test_gzip_CFLAGS = $(WARNINGS_CFLAGS) $(LIBGUESTFS_CFLAGS)
-test_gzip_LDADD = libtest.la $(LIBGUESTFS_LIBS)
-
-disk.gz: disk
- rm -f $@
- gzip -9 -c disk > $@
-endif HAVE_ZLIB
-endif HAVE_MKE2FS_WITH_D
-
# info plugin test.
TESTS += \
test-info-address.sh \
@@ -1253,6 +1236,23 @@ EXTRA_DIST += test-extentlist.sh
TESTS += test-fua.sh
EXTRA_DIST += test-fua.sh
+# gzip filter test.
+if HAVE_MKE2FS_WITH_D
+if HAVE_ZLIB
+LIBGUESTFS_TESTS += test-gzip
+check_DATA += disk.gz
+CLEANFILES += disk.gz
+
+test_gzip_SOURCES = test-gzip.c test.h
+test_gzip_CFLAGS = $(WARNINGS_CFLAGS) $(LIBGUESTFS_CFLAGS)
+test_gzip_LDADD = libtest.la $(LIBGUESTFS_LIBS)
+
+disk.gz: disk
+ rm -f $@
+ gzip -9 -c disk > $@
+endif HAVE_ZLIB
+endif HAVE_MKE2FS_WITH_D
+
# ip filter test.
TESTS += test-ip-filter.sh
EXTRA_DIST += test-ip-filter.sh
diff --git a/filters/gzip/gzip.c b/filters/gzip/gzip.c
new file mode 100644
index 00000000..582652cd
--- /dev/null
+++ b/filters/gzip/gzip.c
@@ -0,0 +1,347 @@
+/* nbdkit
+ * Copyright (C) 2018-2020 Red Hat Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Red Hat nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <pthread.h>
+
+#include <zlib.h>
+
+#include <nbdkit-filter.h>
+
+#include "cleanup.h"
+#include "minmax.h"
+
+/* The first thread to call gzip_prepare has to uncompress the whole
+ * plugin to the temporary file. This lock prevents concurrent
+ * access.
+ */
+static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
+
+/* Temporary file storing the uncompressed data. */
+static int fd = -1;
+
+/* Size of uncompressed data. */
+static int64_t size = -1;
+
+static void
+gzip_unload (void)
+{
+ if (fd >= 0)
+ close (fd);
+}
+
+static int
+gzip_thread_model (void)
+{
+ return NBDKIT_THREAD_MODEL_PARALLEL;
+}
+
+static void *
+gzip_open (nbdkit_next_open *next, nbdkit_backend *nxdata, int readonly)
+{
+ /* Always pass readonly=1 to the underlying plugin. */
+ if (next (nxdata, 1) == -1)
+ return NULL;
+
+ return NBDKIT_HANDLE_NOT_NEEDED;
+}
+
+/* Convert a zlib error (always negative) to an nbdkit error message,
+ * and return errno correctly.
+ */
+static void
+zerror (const char *op, const z_stream *strm, int zerr)
+{
+ if (zerr == Z_MEM_ERROR) {
+ errno = ENOMEM;
+ nbdkit_error ("gzip: %s: %m", op);
+ }
+ else {
+ errno = EIO;
+ if (strm->msg)
+ nbdkit_error ("gzip: %s: %s", op, strm->msg);
+ else
+ nbdkit_error ("gzip: %s: unknown error: %d", op, zerr);
+ }
+}
+
+/* Write a whole buffer to the temporary file or fail. */
+static int
+xwrite (const void *buf, size_t count)
+{
+ ssize_t r;
+
+ while (count > 0) {
+ r = write (fd, buf, count);
+ if (r == -1) {
+ nbdkit_error ("write: %m");
+ return -1;
+ }
+ buf += r;
+ count -= r;
+ }
+
+ return 0;
+}
+
+/* The first thread to call gzip_prepare uncompresses the whole plugin. */
+static int
+do_uncompress (struct nbdkit_next_ops *next_ops, void *nxdata)
+{
+ int64_t compressed_size;
+ z_stream strm;
+ int zerr;
+ const char *tmpdir;
+ size_t len;
+ char *template;
+ CLEANUP_FREE char *in_block = NULL, *out_block = NULL;
+
+ /* This was the same buffer size as used in the old plugin. As far
+ * as I know it was chosen at random.
+ */
+ const size_t block_size = 128 * 1024;
+
+ assert (size == -1);
+
+ /* Get the size of the underlying plugin. */
+ compressed_size = next_ops->get_size (nxdata);
+ if (compressed_size == -1)
+ return -1;
+
+ /* Create the temporary file. */
+ tmpdir = getenv ("TMPDIR");
+ if (!tmpdir)
+ tmpdir = LARGE_TMPDIR;
+
+ len = strlen (tmpdir) + 8;
+ template = alloca (len);
+ snprintf (template, len, "%s/XXXXXX", tmpdir);
+
+#ifdef HAVE_MKOSTEMP
+ fd = mkostemp (template, O_CLOEXEC);
+#else
+ /* This is only invoked serially with the lock held, so this is safe. */
+ fd = mkstemp (template);
+ if (fd >= 0) {
+ fd = set_cloexec (fd);
+ if (fd < 0) {
+ int e = errno;
+ unlink (template);
+ errno = e;
+ }
+ }
+#endif
+ if (fd == -1) {
+ nbdkit_error ("mkostemp: %s: %m", tmpdir);
+ return -1;
+ }
+
+ unlink (template);
+
+ /* Uncompress the whole plugin. This is REQUIRED in order to
+ * implement gzip_get_size. See: https://stackoverflow.com/a/9213826
+ *
+ * For use of inflateInit2 on gzip streams see:
+ * https://stackoverflow.com/a/1838702
+ */
+ memset (&strm, 0, sizeof strm);
+ zerr = inflateInit2 (&strm, 16+MAX_WBITS);
+ if (zerr != Z_OK) {
+ zerror ("inflateInit2", &strm, zerr);
+ return -1;
+ }
+
+ in_block = malloc (block_size);
+ if (!in_block) {
+ nbdkit_error ("malloc: %m");
+ return -1;
+ }
+ out_block = malloc (block_size);
+ if (!out_block) {
+ nbdkit_error ("malloc: %m");
+ return -1;
+ }
+
+ for (;;) {
+ /* Do we need to read more from the plugin? */
+ if (strm.avail_in == 0 && strm.total_in < compressed_size) {
+ size_t n = MIN (block_size, compressed_size - strm.total_in);
+ int err = 0;
+
+ if (next_ops->pread (nxdata, in_block, (uint32_t) n, strm.total_in,
+ 0, &err) == -1) {
+ errno = err;
+ return -1;
+ }
+
+ strm.next_in = (void *) in_block;
+ strm.avail_in = n;
+ }
+
+ /* Inflate the next chunk of input. */
+ strm.next_out = (void *) out_block;
+ strm.avail_out = block_size;
+ zerr = inflate (&strm, Z_SYNC_FLUSH);
+ if (zerr < 0) {
+ zerror ("inflate", &strm, zerr);
+ return -1;
+ }
+
+ /* Write the output to the file. */
+ if (xwrite (out_block, (char *) strm.next_out - out_block) == -1)
+ return -1;
+
+ if (zerr == Z_STREAM_END)
+ break;
+ }
+
+ /* Set the size to the total uncompressed size. */
+ size = strm.total_out;
+ nbdkit_debug ("gzip: uncompressed size: %" PRIi64, size);
+
+ zerr = inflateEnd (&strm);
+ if (zerr != Z_OK) {
+ zerror ("inflateEnd", &strm, zerr);
+ return -1;
+ }
+
+ return 0;
+}
+
+static int
+gzip_prepare (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle,
+ int readonly)
+{
+ ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&lock);
+
+ if (size >= 0)
+ return 0;
+ return do_uncompress (next_ops, nxdata);
+}
+
+/* Whatever the plugin says, this filter makes it read-only. */
+static int
+gzip_can_write (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle)
+{
+ return 0;
+}
+
+/* Similar to above, whatever the plugin says, extents are not
+ * supported.
+ */
+static int
+gzip_can_extents (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle)
+{
+ return 0;
+}
+
+/* We are already operating as a cache regardless of the plugin's
+ * underlying .can_cache, but it's easiest to just rely on nbdkit's
+ * behavior of calling .pread for caching.
+ */
+static int
+gzip_can_cache (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle)
+{
+ return NBDKIT_CACHE_EMULATE;
+}
+
+/* Get the file size. */
+static int64_t
+gzip_get_size (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle)
+{
+ /* This must be true because gzip_prepare must have been called. */
+ assert (size >= 0);
+
+ /* We must call underlying get_size even though we don't use the
+ * result, because it caches the plugin size in server/backend.c.
+ */
+ if (next_ops->get_size (nxdata) == -1)
+ return -1;
+
+ return size;
+}
+
+/* Read data from the temporary file. */
+static int
+gzip_pread (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle, void *buf, uint32_t count, uint64_t offset,
+ uint32_t flags, int *err)
+{
+ /* This must be true because gzip_prepare must have been called. */
+ assert (fd >= 0);
+
+ while (count > 0) {
+ ssize_t r = pread (fd, buf, count, offset);
+ if (r == -1) {
+ nbdkit_error ("pread: %m");
+ return -1;
+ }
+ if (r == 0) {
+ nbdkit_error ("pread: unexpected end of file");
+ return -1;
+ }
+ buf += r;
+ count -= r;
+ offset += r;
+ }
+
+ return 0;
+}
+
+static struct nbdkit_filter filter = {
+ .name = "gzip",
+ .longname = "nbdkit gzip filter",
+ .unload = gzip_unload,
+ .thread_model = gzip_thread_model,
+ .open = gzip_open,
+ .prepare = gzip_prepare,
+ .can_write = gzip_can_write,
+ .can_extents = gzip_can_extents,
+ .can_cache = gzip_can_cache,
+ .prepare = gzip_prepare,
+ .get_size = gzip_get_size,
+ .pread = gzip_pread,
+};
+
+NBDKIT_REGISTER_FILTER(filter)
diff --git a/tests/test-gzip.c b/tests/test-gzip.c
index 9e1229e1..969d6d0e 100644
--- a/tests/test-gzip.c
+++ b/tests/test-gzip.c
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013 Red Hat Inc.
+ * Copyright (C) 2013-2020 Red Hat Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
@@ -50,7 +50,7 @@ main (int argc, char *argv[])
int r;
char *data;
- if (test_start_nbdkit ("gzip", "-r", "file=disk.gz", NULL) == -1)
+ if (test_start_nbdkit ("file", "--filter=gzip", "disk.gz", NULL) == -1)
exit (EXIT_FAILURE);
g = guestfs_create ();
diff --git a/TODO b/TODO
index 28bcc952..addf8025 100644
--- a/TODO
+++ b/TODO
@@ -169,8 +169,6 @@ Rust:
Suggestions for filters
-----------------------
-* gzip plugin should really be a filter
-
* LUKS encrypt/decrypt filter, bonus points if compatible with qemu
LUKS-encrypted disk images
--
2.27.0
More information about the Libguestfs
mailing list