io: add a QIOChannelNull equivalent to /dev/null

This is for code which needs a portable equivalent to a QIOChannelFile
connected to /dev/null.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2022-06-20 12:01:45 +01:00 committed by Dr. David Alan Gilbert
parent 1abaec9a1b
commit 87e4276449
6 changed files with 392 additions and 0 deletions

55
include/io/channel-null.h Normal file
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@ -0,0 +1,55 @@
/*
* QEMU I/O channels null driver
*
* Copyright (c) 2022 Red Hat, Inc.
*
* 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 2.1 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, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef QIO_CHANNEL_FILE_H
#define QIO_CHANNEL_FILE_H
#include "io/channel.h"
#include "qom/object.h"
#define TYPE_QIO_CHANNEL_NULL "qio-channel-null"
OBJECT_DECLARE_SIMPLE_TYPE(QIOChannelNull, QIO_CHANNEL_NULL)
/**
* QIOChannelNull:
*
* The QIOChannelNull object provides a channel implementation
* that discards all writes and returns EOF for all reads.
*/
struct QIOChannelNull {
QIOChannel parent;
bool closed;
};
/**
* qio_channel_null_new:
*
* Create a new IO channel object that discards all writes
* and returns EOF for all reads.
*
* Returns: the new channel object
*/
QIOChannelNull *
qio_channel_null_new(void);
#endif /* QIO_CHANNEL_NULL_H */

237
io/channel-null.c Normal file
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@ -0,0 +1,237 @@
/*
* QEMU I/O channels null driver
*
* Copyright (c) 2022 Red Hat, Inc.
*
* 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 2.1 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, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "io/channel-null.h"
#include "io/channel-watch.h"
#include "qapi/error.h"
#include "trace.h"
#include "qemu/iov.h"
typedef struct QIOChannelNullSource QIOChannelNullSource;
struct QIOChannelNullSource {
GSource parent;
QIOChannel *ioc;
GIOCondition condition;
};
QIOChannelNull *
qio_channel_null_new(void)
{
QIOChannelNull *ioc;
ioc = QIO_CHANNEL_NULL(object_new(TYPE_QIO_CHANNEL_NULL));
trace_qio_channel_null_new(ioc);
return ioc;
}
static void
qio_channel_null_init(Object *obj)
{
QIOChannelNull *ioc = QIO_CHANNEL_NULL(obj);
ioc->closed = false;
}
static ssize_t
qio_channel_null_readv(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int **fds G_GNUC_UNUSED,
size_t *nfds G_GNUC_UNUSED,
Error **errp)
{
QIOChannelNull *nioc = QIO_CHANNEL_NULL(ioc);
if (nioc->closed) {
error_setg_errno(errp, EINVAL,
"Channel is closed");
return -1;
}
return 0;
}
static ssize_t
qio_channel_null_writev(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int *fds G_GNUC_UNUSED,
size_t nfds G_GNUC_UNUSED,
int flags G_GNUC_UNUSED,
Error **errp)
{
QIOChannelNull *nioc = QIO_CHANNEL_NULL(ioc);
if (nioc->closed) {
error_setg_errno(errp, EINVAL,
"Channel is closed");
return -1;
}
return iov_size(iov, niov);
}
static int
qio_channel_null_set_blocking(QIOChannel *ioc G_GNUC_UNUSED,
bool enabled G_GNUC_UNUSED,
Error **errp G_GNUC_UNUSED)
{
return 0;
}
static off_t
qio_channel_null_seek(QIOChannel *ioc G_GNUC_UNUSED,
off_t offset G_GNUC_UNUSED,
int whence G_GNUC_UNUSED,
Error **errp G_GNUC_UNUSED)
{
return 0;
}
static int
qio_channel_null_close(QIOChannel *ioc,
Error **errp G_GNUC_UNUSED)
{
QIOChannelNull *nioc = QIO_CHANNEL_NULL(ioc);
nioc->closed = true;
return 0;
}
static void
qio_channel_null_set_aio_fd_handler(QIOChannel *ioc G_GNUC_UNUSED,
AioContext *ctx G_GNUC_UNUSED,
IOHandler *io_read G_GNUC_UNUSED,
IOHandler *io_write G_GNUC_UNUSED,
void *opaque G_GNUC_UNUSED)
{
}
static gboolean
qio_channel_null_source_prepare(GSource *source G_GNUC_UNUSED,
gint *timeout)
{
*timeout = -1;
return TRUE;
}
static gboolean
qio_channel_null_source_check(GSource *source G_GNUC_UNUSED)
{
return TRUE;
}
static gboolean
qio_channel_null_source_dispatch(GSource *source,
GSourceFunc callback,
gpointer user_data)
{
QIOChannelFunc func = (QIOChannelFunc)callback;
QIOChannelNullSource *ssource = (QIOChannelNullSource *)source;
return (*func)(ssource->ioc,
ssource->condition,
user_data);
}
static void
qio_channel_null_source_finalize(GSource *source)
{
QIOChannelNullSource *ssource = (QIOChannelNullSource *)source;
object_unref(OBJECT(ssource->ioc));
}
GSourceFuncs qio_channel_null_source_funcs = {
qio_channel_null_source_prepare,
qio_channel_null_source_check,
qio_channel_null_source_dispatch,
qio_channel_null_source_finalize
};
static GSource *
qio_channel_null_create_watch(QIOChannel *ioc,
GIOCondition condition)
{
GSource *source;
QIOChannelNullSource *ssource;
source = g_source_new(&qio_channel_null_source_funcs,
sizeof(QIOChannelNullSource));
ssource = (QIOChannelNullSource *)source;
ssource->ioc = ioc;
object_ref(OBJECT(ioc));
ssource->condition = condition;
return source;
}
static void
qio_channel_null_class_init(ObjectClass *klass,
void *class_data G_GNUC_UNUSED)
{
QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
ioc_klass->io_writev = qio_channel_null_writev;
ioc_klass->io_readv = qio_channel_null_readv;
ioc_klass->io_set_blocking = qio_channel_null_set_blocking;
ioc_klass->io_seek = qio_channel_null_seek;
ioc_klass->io_close = qio_channel_null_close;
ioc_klass->io_create_watch = qio_channel_null_create_watch;
ioc_klass->io_set_aio_fd_handler = qio_channel_null_set_aio_fd_handler;
}
static const TypeInfo qio_channel_null_info = {
.parent = TYPE_QIO_CHANNEL,
.name = TYPE_QIO_CHANNEL_NULL,
.instance_size = sizeof(QIOChannelNull),
.instance_init = qio_channel_null_init,
.class_init = qio_channel_null_class_init,
};
static void
qio_channel_null_register_types(void)
{
type_register_static(&qio_channel_null_info);
}
type_init(qio_channel_null_register_types);

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@ -3,6 +3,7 @@ io_ss.add(files(
'channel-buffer.c',
'channel-command.c',
'channel-file.c',
'channel-null.c',
'channel-socket.c',
'channel-tls.c',
'channel-util.c',

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@ -10,6 +10,9 @@ qio_task_thread_result(void *task) "Task thread result task=%p"
qio_task_thread_source_attach(void *task, void *source) "Task thread source attach task=%p source=%p"
qio_task_thread_source_cancel(void *task, void *source) "Task thread source cancel task=%p source=%p"
# channel-null.c
qio_channel_null_new(void *ioc) "Null new ioc=%p"
# channel-socket.c
qio_channel_socket_new(void *ioc) "Socket new ioc=%p"
qio_channel_socket_new_fd(void *ioc, int fd) "Socket new ioc=%p fd=%d"

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@ -88,6 +88,7 @@ if have_block
'test-io-channel-file': ['io-channel-helpers.c', io],
'test-io-channel-command': ['io-channel-helpers.c', io],
'test-io-channel-buffer': ['io-channel-helpers.c', io],
'test-io-channel-null': [io],
'test-crypto-ivgen': [io],
'test-crypto-afsplit': [io],
'test-crypto-block': [io],

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@ -0,0 +1,95 @@
/*
* QEMU I/O channel null test
*
* Copyright (c) 2022 Red Hat, Inc.
*
* 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 2.1 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, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "io/channel-null.h"
#include "qapi/error.h"
static gboolean test_io_channel_watch(QIOChannel *ioc,
GIOCondition condition,
gpointer opaque)
{
GIOCondition *gotcond = opaque;
*gotcond = condition;
return G_SOURCE_REMOVE;
}
static void test_io_channel_null_io(void)
{
g_autoptr(QIOChannelNull) null = qio_channel_null_new();
char buf[1024];
GIOCondition gotcond = 0;
Error *local_err = NULL;
g_assert(qio_channel_write(QIO_CHANNEL(null),
"Hello World", 11,
&error_abort) == 11);
g_assert(qio_channel_read(QIO_CHANNEL(null),
buf, sizeof(buf),
&error_abort) == 0);
qio_channel_add_watch(QIO_CHANNEL(null),
G_IO_IN,
test_io_channel_watch,
&gotcond,
NULL);
g_main_context_iteration(NULL, false);
g_assert(gotcond == G_IO_IN);
qio_channel_add_watch(QIO_CHANNEL(null),
G_IO_IN | G_IO_OUT,
test_io_channel_watch,
&gotcond,
NULL);
g_main_context_iteration(NULL, false);
g_assert(gotcond == (G_IO_IN | G_IO_OUT));
qio_channel_close(QIO_CHANNEL(null), &error_abort);
g_assert(qio_channel_write(QIO_CHANNEL(null),
"Hello World", 11,
&local_err) == -1);
g_assert_nonnull(local_err);
g_clear_pointer(&local_err, error_free);
g_assert(qio_channel_read(QIO_CHANNEL(null),
buf, sizeof(buf),
&local_err) == -1);
g_assert_nonnull(local_err);
g_clear_pointer(&local_err, error_free);
}
int main(int argc, char **argv)
{
module_call_init(MODULE_INIT_QOM);
g_test_init(&argc, &argv, NULL);
g_test_add_func("/io/channel/null/io", test_io_channel_null_io);
return g_test_run();
}