[Qemu-devel] [PATCH v1 RFC 24/34] io: add QIOChannelFile class

["Daniel P. Berrange" <berrange@redhat.com>]

Add a QIOChannel subclass that is capable of operating on things
that are files, such as plain files, pipes, character/block
devices, but notably not sockets.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 include/io/channel-file.h |  67 ++++++++++++++++
 io/Makefile.objs          |   1 +
 io/channel-file.c         | 198 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 266 insertions(+)
 create mode 100644 include/io/channel-file.h
 create mode 100644 io/channel-file.c

diff --git a/include/io/channel-file.h b/include/io/channel-file.h
new file mode 100644
index 0000000..6bbbe5d
--- /dev/null
+++ b/include/io/channel-file.h
@@ -0,0 +1,67 @@
+/*
+ * QEMU I/O channels files driver
+ *
+ * Copyright (c) 2015 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 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"
+
+#define TYPE_QIO_CHANNEL_FILE "qemu:io-channel-file"
+#define QIO_CHANNEL_FILE(obj)                                     \
+    OBJECT_CHECK(QIOChannelFile, (obj), TYPE_QIO_CHANNEL_FILE)
+
+typedef struct _QIOChannelFile QIOChannelFile;
+
+/**
+ * QIOChannelFile:
+ *
+ * The QIOChannelFile object provides a channel implementation
+ * that is able to perform I/O on block devices, character
+ * devices, FIFOs, pipes and plain files. While it is technically
+ * able to work on sockets too on the UNIX platform, this is not
+ * portable to Windows and lacks some extra sockets specific
+ * functionality. So the QIOChannelSocket object is recommended
+ * for that use case.
+ *
+ */
+
+struct _QIOChannelFile {
+    QIOChannel parent;
+    int fd;
+};
+
+
+/**
+ * qio_channel_file_new_fd:
+ * @fd: the file descriptor
+ *
+ * Create a new IO channel object for a file represented
+ * by the @fd parameter. @fd can be associated with a
+ * block device, character device, fifo, pipe, or a
+ * regular file. For sockets, the QIOChannelSocket class
+ * should be used instead, as this provides greater
+ * functionality and cross platform portability.
+ *
+ * Returns: the new channel object
+ */
+QIOChannelFile *
+qio_channel_file_new_fd(int fd);
+
+#endif /* QIO_CHANNEL_FILE_H__ */
diff --git a/io/Makefile.objs b/io/Makefile.objs
index 4f5e276..eec1b43 100644
--- a/io/Makefile.objs
+++ b/io/Makefile.objs
@@ -1,3 +1,4 @@
 util-obj-y += channel.o
 util-obj-y += channel-unix.o
 util-obj-y += channel-socket.o
+util-obj-y += channel-file.o
diff --git a/io/channel-file.c b/io/channel-file.c
new file mode 100644
index 0000000..4da3ce1
--- /dev/null
+++ b/io/channel-file.c
@@ -0,0 +1,198 @@
+/*
+ * QEMU I/O channels files driver
+ *
+ * Copyright (c) 2015 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 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 <glib/gi18n.h>
+
+#include "io/channel-file.h"
+#include "io/channel-unix.h"
+#include "qemu/sockets.h"
+
+QIOChannelFile *
+qio_channel_file_new_fd(int fd)
+{
+    QIOChannelFile *ioc;
+
+    ioc = QIO_CHANNEL_FILE(object_new(TYPE_QIO_CHANNEL_FILE));
+
+    ioc->fd = fd;
+
+    return ioc;
+}
+
+
+static void qio_channel_file_init(Object *obj)
+{
+    QIOChannelFile *ioc = QIO_CHANNEL_FILE(obj);
+    ioc->fd = -1;
+}
+
+static void qio_channel_file_finalize(Object *obj)
+{
+    QIOChannelFile *ioc = QIO_CHANNEL_FILE(obj);
+    if (ioc->fd != -1) {
+        close(ioc->fd);
+        ioc->fd = -1;
+    }
+}
+
+
+static ssize_t qio_channel_file_readv(QIOChannel *ioc,
+                                      const struct iovec *iov,
+                                      size_t niov,
+                                      int **fds,
+                                      size_t *nfds,
+                                      int flags,
+                                      Error **errp)
+{
+    QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
+    ssize_t ret;
+
+    if (flags) {
+        error_setg_errno(errp, EINVAL,
+                         _("Flags %x are not supported"),
+                         flags);
+        return -1;
+    }
+    if (fds || nfds) {
+        error_setg_errno(errp, EINVAL, "%s",
+                         _("Channel does not support file descriptor passing"));
+        return -1;
+    }
+
+ retry:
+    ret = readv(fioc->fd, iov, niov);
+    if (ret < 0) {
+        if (errno == EAGAIN) {
+            return -2;
+        }
+        if (errno == EINTR) {
+            goto retry;
+        }
+
+        error_setg_errno(errp, errno, "%s",
+                         _("Unable to read from file"));
+        return -1;
+    }
+
+    return ret;
+}
+
+static ssize_t qio_channel_file_writev(QIOChannel *ioc,
+                                       const struct iovec *iov,
+                                       size_t niov,
+                                       int *fds,
+                                       size_t nfds,
+                                       int flags G_GNUC_UNUSED,
+                                       Error **errp)
+{
+    QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
+    ssize_t ret;
+
+    if (flags) {
+        error_setg_errno(errp, EINVAL,
+                         _("Flags %x are not supported"),
+                         flags);
+        return -1;
+    }
+    if (fds || nfds) {
+        error_setg_errno(errp, EINVAL, "%s",
+                         _("Channel does not support file descriptor passing"));
+        return -1;
+    }
+
+ retry:
+    ret = writev(fioc->fd, iov, niov);
+    if (ret <= 0) {
+        if (errno == EAGAIN) {
+            return -2;
+        }
+        if (errno == EINTR) {
+            goto retry;
+        }
+        error_setg_errno(errp, errno, "%s",
+                         _("Unable to write to file"));
+        return -1;
+    }
+    return ret;
+}
+
+static void qio_channel_file_set_blocking(QIOChannel *ioc,
+                                          bool enabled)
+{
+    QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
+
+    if (enabled) {
+        qemu_set_block(fioc->fd);
+    } else {
+        qemu_set_nonblock(fioc->fd);
+    }
+}
+
+
+static int qio_channel_file_close(QIOChannel *ioc,
+                                  Error **errp)
+{
+    QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
+
+    if (close(fioc->fd) < 0) {
+        error_setg_errno(errp, errno, "%s",
+                         _("Unable to close file"));
+        return -1;
+    }
+    return 0;
+}
+
+
+static GSource *qio_channel_file_create_watch(QIOChannel *ioc,
+                                              GIOCondition condition)
+{
+    QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
+    return qio_channel_unix_create_fd_watch(ioc,
+                                            fioc->fd,
+                                            condition);
+}
+
+static void qio_channel_file_class_init(ObjectClass *klass,
+                                        void *class_data G_GNUC_UNUSED)
+{
+    QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
+
+    ioc_klass->io_writev = qio_channel_file_writev;
+    ioc_klass->io_readv = qio_channel_file_readv;
+    ioc_klass->io_set_blocking = qio_channel_file_set_blocking;
+    ioc_klass->io_close = qio_channel_file_close;
+    ioc_klass->io_create_watch = qio_channel_file_create_watch;
+}
+
+static const TypeInfo qio_channel_file_info = {
+    .parent = TYPE_QIO_CHANNEL,
+    .name = TYPE_QIO_CHANNEL_FILE,
+    .instance_size = sizeof(QIOChannelFile),
+    .instance_init = qio_channel_file_init,
+    .instance_finalize = qio_channel_file_finalize,
+    .class_init = qio_channel_file_class_init,
+};
+
+static void qio_channel_file_register_types(void)
+{
+    type_register_static(&qio_channel_file_info);
+}
+
+type_init(qio_channel_file_register_types);
-- 
2.1.0