[PATCH v3 04/14] io: Add generic pwritev/preadv interface

[Nikolay Borisov]

Introduce basic pwriteve/preadv support in the generic channel layer.
SPecific implementation will follow for the file channel as this is
required in order to support migration streams with fixed location of
each ram page.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 include/io/channel.h | 49 ++++++++++++++++++++++++++++++++++++++++++++
 io/channel.c         | 26 +++++++++++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/include/io/channel.h b/include/io/channel.h
index c680ee748021..6b10bce8bbdf 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -124,6 +124,16 @@ struct QIOChannelClass {
                            Error **errp);
 
     /* Optional callbacks */
+    ssize_t (*io_pwritev)(QIOChannel *ioc,
+                       const struct iovec *iov,
+                       size_t niov,
+                       off_t offset,
+                       Error **errp);
+    ssize_t (*io_preadv)(QIOChannel *ioc,
+                      const struct iovec *iov,
+                      size_t niov,
+                      off_t offset,
+                      Error **errp);
     int (*io_shutdown)(QIOChannel *ioc,
                        QIOChannelShutdown how,
                        Error **errp);
@@ -504,6 +514,45 @@ int qio_channel_set_blocking(QIOChannel *ioc,
 int qio_channel_close(QIOChannel *ioc,
                       Error **errp);
 
+
+/**
+ * qio_channel_io_pwritev
+ * @ioc: the channel object
+ * @iov: the array of memory regions to write data from
+ * @niov: the length of the @iov array
+ * @offset: offset in the channel where writes should begin
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Not all implementations will support this facility, so may report an error.
+ * To avoid errors, the caller may check for the feature flag
+ * QIO_CHANNEL_FEATURE_SEEKABLE prior to calling this method.
+ *
+ * Behaves as qio_channel_writev_full, apart from not supporting sending of 
file
+ * handles as well as beginning the write at the passed @offset
+ *
+ */
+ssize_t qio_channel_io_pwritev(QIOChannel *ioc, const struct iovec *iov,
+                               size_t niov, off_t offset, Error **errp);
+
+
+/**
+ * qio_channel_io_preadv
+ * @ioc: the channel object
+ * @iov: the array of memory regions to read data into
+ * @niov: the length of the @iov array
+ * @offset: offset in the channel where writes should begin
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Not all implementations will support this facility, so may report an error.
+ * To avoid errors, the caller may check for the feature flag
+ * QIO_CHANNEL_FEATURE_SEEKABLE prior to calling this method.
+ *
+ * Behaves as qio_channel_readv_full, apart from not supporting receiving of 
file
+ * handles as well as beginning the read at the passed @offset
+ *
+ */
+ssize_t qio_channel_io_preadv(QIOChannel *ioc, const struct iovec *iov,
+                             size_t niov, off_t offset, Error **errp);
 /**
  * qio_channel_shutdown:
  * @ioc: the channel object
diff --git a/io/channel.c b/io/channel.c
index 0640941ac573..f5ac9499a7ad 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -437,6 +437,32 @@ GSource *qio_channel_add_watch_source(QIOChannel *ioc,
 }
 
 
+ssize_t qio_channel_io_pwritev(QIOChannel *ioc, const struct iovec *iov,
+                               size_t niov, off_t offset, Error **errp)
+{
+    QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
+
+    if (!klass->io_pwritev) {
+        error_setg(errp, "Channel does not support pwritev");
+        return -1;
+    }
+
+    return klass->io_pwritev(ioc, iov, niov, offset, errp);
+}
+
+ssize_t qio_channel_io_preadv(QIOChannel *ioc, const struct iovec *iov,
+                               size_t niov, off_t offset, Error **errp)
+{
+    QIOChannelClass *klass = QIO_CHANNEL_GET_CLASS(ioc);
+
+    if (!klass->io_preadv) {
+        error_setg(errp, "Channel does not support preadv");
+        return -1;
+    }
+
+    return klass->io_preadv(ioc, iov, niov, offset, errp);
+}
+
 int qio_channel_shutdown(QIOChannel *ioc,
                          QIOChannelShutdown how,
                          Error **errp)
-- 
2.34.1