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buffer: make the Buffer capacity increase in powers of two

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

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 1446203414-4013-2-git-send-email-kraxel@redhat.com

[ rebased to util/buffer.c ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Peter Lieven 2015-10-30 12:09:56 +01:00 committed by Gerd Hoffmann
parent 79cf9fad34
commit 5c10dbb7b5
1 changed files with 4 additions and 1 deletions
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5
util/buffer.c
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@ -20,10 +20,13 @@
#include "qemu/buffer.h" #include "qemu/buffer.h"
#define BUFFER_MIN_INIT_SIZE 4096
void buffer_reserve(Buffer *buffer, size_t len) void buffer_reserve(Buffer *buffer, size_t len)
{ {
if ((buffer->capacity - buffer->offset) < len) { if ((buffer->capacity - buffer->offset) < len) {
buffer->capacity += (len + 1024); buffer->capacity = pow2ceil(buffer->offset + len);
buffer->capacity = MAX(buffer->capacity, BUFFER_MIN_INIT_SIZE);
buffer->buffer = g_realloc(buffer->buffer, buffer->capacity); buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
} }
} }