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
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@ -51,6 +51,16 @@ struct Buffer {
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void buffer_init(Buffer *buffer, const char *name, ...)
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void buffer_init(Buffer *buffer, const char *name, ...)
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GCC_FMT_ATTR(2, 3);
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GCC_FMT_ATTR(2, 3);
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/**
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* buffer_shrink:
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* @buffer: the buffer object
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*
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* Try to shrink the buffer. Checks current buffer capacity and size
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* and reduces capacity in case only a fraction of the buffer is
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* actually used.
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*/
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void buffer_shrink(Buffer *buffer);
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/**
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/**
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* buffer_reserve:
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* buffer_reserve:
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* @buffer: the buffer object
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* @buffer: the buffer object
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@ -21,6 +21,7 @@
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#include "qemu/buffer.h"
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#include "qemu/buffer.h"
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#define BUFFER_MIN_INIT_SIZE 4096
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#define BUFFER_MIN_INIT_SIZE 4096
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#define BUFFER_MIN_SHRINK_SIZE 65536
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void buffer_init(Buffer *buffer, const char *name, ...)
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void buffer_init(Buffer *buffer, const char *name, ...)
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{
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{
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@ -31,6 +32,23 @@ void buffer_init(Buffer *buffer, const char *name, ...)
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va_end(ap);
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va_end(ap);
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}
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}
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void buffer_shrink(Buffer *buffer)
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{
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/*
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* Only shrink in case the used size is *much* smaller than the
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* capacity, to avoid bumping up & down the buffers all the time.
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* realloc() isn't exactly cheap ...
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*/
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if (buffer->offset < (buffer->capacity >> 3) &&
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buffer->capacity > BUFFER_MIN_SHRINK_SIZE) {
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return;
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}
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buffer->capacity = pow2ceil(buffer->offset);
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buffer->capacity = MAX(buffer->capacity, BUFFER_MIN_SHRINK_SIZE);
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buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
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}
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void buffer_reserve(Buffer *buffer, size_t len)
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void buffer_reserve(Buffer *buffer, size_t len)
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{
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{
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if ((buffer->capacity - buffer->offset) < len) {
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if ((buffer->capacity - buffer->offset) < len) {
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