[Qemu-devel] [PATCH 1/4] vnc: make the Buffer capacity increase in powers of two

[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>
---
 ui/vnc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ui/vnc.c b/ui/vnc.c
index caf82f5..8cfd2d8 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -653,10 +653,13 @@ void vnc_framebuffer_update(VncState *vs, int x, int y, int w, int h,
     vnc_write_s32(vs, encoding);
 }
 
+#define BUFFER_MIN_INIT_SIZE 4096
+
 void buffer_reserve(Buffer *buffer, size_t len)
 {
     if ((buffer->capacity - buffer->offset) < len) {
-        buffer->capacity += (len + 1024);
+        buffer->capacity = pow2ceil(buffer->capacity + len);
+        buffer->capacity = MAX(buffer->capacity, BUFFER_MIN_INIT_SIZE);
         buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
     }
 }
-- 
1.9.1