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buffer: add buffer_shrink 

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: 1446203414-4013-6-git-send-email-kraxel@redhat.com
This commit is contained in:
Gerd Hoffmann 2015-10-30 12:10:00 +01:00
parent 830a958320
commit 1ff36b5d4d
2 changed files with 29 additions and 1 deletions
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10
include/qemu/buffer.h
View File

@ -51,6 +51,16 @@ struct Buffer {
void buffer_init(Buffer *buffer, const char *name, ...)
GCC_FMT_ATTR(2, 3);
/**
* buffer_shrink:
* @buffer: the buffer object
*
* Try to shrink the buffer. Checks current buffer capacity and size
* and reduces capacity in case only a fraction of the buffer is
* actually used.
*/
void buffer_shrink(Buffer *buffer);
/**
* buffer_reserve:
* @buffer: the buffer object

20
util/buffer.c
View File

@ -20,7 +20,8 @@
#include "qemu/buffer.h"
#define BUFFER_MIN_INIT_SIZE 4096
#define BUFFER_MIN_INIT_SIZE 4096
#define BUFFER_MIN_SHRINK_SIZE 65536
void buffer_init(Buffer *buffer, const char *name, ...)
{
@ -31,6 +32,23 @@ void buffer_init(Buffer *buffer, const char *name, ...)
va_end(ap);
}
void buffer_shrink(Buffer *buffer)
{
/*
* Only shrink in case the used size is *much* smaller than the
* capacity, to avoid bumping up & down the buffers all the time.
* realloc() isn't exactly cheap ...
*/
if (buffer->offset < (buffer->capacity >> 3) &&
buffer->capacity > BUFFER_MIN_SHRINK_SIZE) {
return;
}
buffer->capacity = pow2ceil(buffer->offset);
buffer->capacity = MAX(buffer->capacity, BUFFER_MIN_SHRINK_SIZE);
buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
}
void buffer_reserve(Buffer *buffer, size_t len)
{
if ((buffer->capacity - buffer->offset) < len) {