[Qemu-devel] [RfC PATCH 03/10] vnc: make the Buffer capacity increase in powers of two

[Gerd Hoffmann <kraxel@redhat.com>]

From: Peter Lieven <pl@kamp.de>

This makes sure the number of reallocs is in O(log N).

Signed-off-by: Peter Lieven <pl@kamp.de>

[ rebased to io/buffer.c ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 io/buffer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/io/buffer.c b/io/buffer.c
index 68ae68d..6aa06e7 100644
--- a/io/buffer.c
+++ b/io/buffer.c
@@ -20,10 +20,13 @@
 
 #include "io/buffer.h"
 
+#define QIO_BUFFER_MIN_INIT_SIZE 4096
+
 void qio_buffer_reserve(QIOBuffer *buffer, size_t len)
 {
     if ((buffer->capacity - buffer->offset) < len) {
-        buffer->capacity += (len + 1024);
+        buffer->capacity = pow2ceil(buffer->offset + len);
+        buffer->capacity = MAX(buffer->capacity, QIO_BUFFER_MIN_INIT_SIZE);
         buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
     }
 }
-- 
1.8.3.1