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/*
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 *  lru lists are circular with a list head
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 *  pointing to the start and end of the list
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 */
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#include <u.h>
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#include "lru.h"
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/*
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 *  Create an lru chain of buffers
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 */
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void
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lruinit(Lru *h)
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{
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	h->lprev = h->lnext = h;
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}
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/*
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 *  Add a member to an lru chain
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 */
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void
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lruadd(Lru *h, Lru *m)
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{
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	h->lprev->lnext = m;
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	m->lprev = h->lprev;
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	h->lprev = m;
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	m->lnext = h;
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}
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/*
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 *  Move to end of lru list
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 */
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void
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lruref(Lru *h, Lru *m)
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{
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	if(h->lprev == m)
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		return;		/* alread at end of list */
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	/*
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	 *  remove from list
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	 */
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	m->lprev->lnext = m->lnext;
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	m->lnext->lprev = m->lprev;
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	/*
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	 *  add in at end
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	 */
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	h->lprev->lnext = m;
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	m->lprev = h->lprev;
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	h->lprev = m;
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	m->lnext = h;
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}
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/*
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 *  Move to head of lru list
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 */
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void
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lruderef(Lru *h, Lru *m)
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{
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	if(h->lnext == m)
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		return;		/* alread at head of list */
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	/*
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	 *  remove from list
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	 */
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	m->lprev->lnext = m->lnext;
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	m->lnext->lprev = m->lprev;
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	/*
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	 *  add in at head
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	 */
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	h->lnext->lprev = m;
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	m->lnext = h->lnext;
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	h->lnext = m;
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	m->lprev = h;
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}