buffer: add buffer_move

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1446203414-4013-5-git-send-email-kraxel@redhat.com

include/qemu/buffer.h

@@ -137,4 +137,14 @@ gboolean buffer_empty(Buffer *buffer);
  */
 void buffer_move_empty(Buffer *to, Buffer *from);
 
+/**
+ * buffer_move:
+ * @to: destination buffer object
+ * @from: source buffer object
+ *
+ * Moves buffer, copying data (unless 'to' buffer happens to be empty).
+ * 'from' buffer is empty and zero-sized on return.
+ */
+void buffer_move(Buffer *to, Buffer *from);
+
 #endif /* QEMU_BUFFER_H__ */

util/buffer.c

@@ -91,3 +91,19 @@ void buffer_move_empty(Buffer *to, Buffer *from)
     from->capacity = 0;
     from->buffer = NULL;
 }
+
+void buffer_move(Buffer *to, Buffer *from)
+{
+    if (to->offset == 0) {
+        buffer_move_empty(to, from);
+        return;
+    }
+
+    buffer_reserve(to, from->offset);
+    buffer_append(to, from->buffer, from->offset);
+
+    g_free(from->buffer);
+    from->offset = 0;
+    from->capacity = 0;
+    from->buffer = NULL;
+}