[PATCH v3 12/25] xen: Let buffer_append() return the size consumed

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

The buffer.size and buffer.consumed fields are only updated within the
buffer_append() body. We can simply let buffer_append() return the
difference (the buffer consumed).

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 hw/char/xen_console.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index 083b2c8e2a..1a30014a11 100644
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -48,7 +48,7 @@ struct XenConsole {
     int               backlog;
 };
 
-static void buffer_append(struct XenConsole *con)
+static ssize_t buffer_append(struct XenConsole *con)
 {
     struct buffer *buffer = &con->buffer;
     XENCONS_RING_IDX cons, prod, size;
@@ -59,8 +59,9 @@ static void buffer_append(struct XenConsole *con)
     xen_mb();
 
     size = prod - cons;
-    if ((size == 0) || (size > sizeof(intf->out)))
-        return;
+    if ((size == 0) || (size > sizeof(intf->out))) {
+        goto out;
+    }
 
     if ((buffer->capacity - buffer->size) < size) {
         buffer->capacity += (size + 1024);
@@ -89,6 +90,9 @@ static void buffer_append(struct XenConsole *con)
         if (buffer->consumed > buffer->max_capacity - over)
             buffer->consumed = buffer->max_capacity - over;
     }
+
+ out:
+    return buffer->size - buffer->consumed;
 }
 
 static void buffer_advance(struct buffer *buffer, size_t len)
@@ -281,8 +285,7 @@ static void con_event(struct XenLegacyDevice *xendev)
     struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);
     ssize_t size;
 
-    buffer_append(con);
-    size = con->buffer.size - con->buffer.consumed;
+    size = buffer_append(con);
     if (size) {
         xencons_send(con, size);
     }
-- 
2.20.1


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