[Spice-devel] [PATCH spice-server 1/3] red-stream: Define interface for manual flush

[Frediano Ziglio]

The writing to network was always immediate.
Every write in the stream causes a write to the OS.
This can have some penalty if you don't write large data as network
packets can be more fragmented or you encrypt data in smaller chunks
(when data are encrypted some padding is added then data is split in
multiple of encryption block which is usually the size of encryption
key and this is done for every write).
Define an interface to allow higher levels code to tell low level when
data should be sent to remote or when can wait more data.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 server/red-stream.c |  9 +++++++++
 server/red-stream.h | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/server/red-stream.c b/server/red-stream.c
index bdc8bc1f..9a9c1a0f 100644
--- a/server/red-stream.c
+++ b/server/red-stream.c
@@ -203,6 +203,15 @@ bool red_stream_write_all(RedStream *stream, const void *in_buf, size_t n)
     return true;
 }
 
+bool red_stream_set_auto_flush(RedStream *s, bool auto_flush)
+{
+    return auto_flush;
+}
+
+void red_stream_flush(RedStream *s)
+{
+}
+
 #if HAVE_SASL
 static ssize_t red_stream_sasl_write(RedStream *s, const void *buf, size_t nbyte);
 #endif
diff --git a/server/red-stream.h b/server/red-stream.h
index 4d5075ed..15af0a59 100644
--- a/server/red-stream.h
+++ b/server/red-stream.h
@@ -69,6 +69,26 @@ bool red_stream_set_no_delay(RedStream *stream, bool no_delay);
 int red_stream_get_no_delay(RedStream *stream);
 int red_stream_send_msgfd(RedStream *stream, int fd);
 
+/**
+ * Set auto flush flag.
+ * If set, stream will send data to the underlying socket as
+ * soon as data are written. This is the default.
+ * If not set, you should call red_stream_flush to force
+ * data to be sent. Failing to call red_stream_flush on a
+ * manual flush stream could lead to latency.
+ * Disabling auto flush can fail while enabling cannot.
+ *
+ * Returns true on success or false on failure.
+ */
+bool red_stream_set_auto_flush(RedStream *stream, bool auto_flush);
+
+/**
+ * Flush data to the underlying socket.
+ * Calling this function on a stream with auto flush set has
+ * no result.
+ */
+void red_stream_flush(RedStream *stream);
+
 typedef enum {
     RED_SASL_ERROR_OK,
     RED_SASL_ERROR_GENERIC,
-- 
2.14.3