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>

2 files changed, 96 insertions, 0 deletions

diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 287b367..b497a41 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -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],
diff --git a/tests/unit/test-io-channel-null.c b/tests/unit/test-io-channel-null.c
new file mode 100644
index 0000000..b3aab17
--- /dev/null
+++ b/tests/unit/test-io-channel-null.c
@@ -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();
+}