Subversion Repositories planix.SVN

/*
 *  lru lists are circular with a list head
 *  pointing to the start and end of the list
 */
#include <u.h>
#include "lru.h"

/*
 *  Create an lru chain of buffers
 */
void
lruinit(Lru *h)
{
        h->lprev = h->lnext = h;
}

/*
 *  Add a member to an lru chain
 */
void
lruadd(Lru *h, Lru *m)
{
        h->lprev->lnext = m;
        m->lprev = h->lprev;
        h->lprev = m;
        m->lnext = h;
}

/*
 *  Move to end of lru list
 */
void
lruref(Lru *h, Lru *m)
{
        if(h->lprev == m)
                return;         /* alread at end of list */

        /*
         *  remove from list
         */
        m->lprev->lnext = m->lnext;
        m->lnext->lprev = m->lprev;

        /*
         *  add in at end
         */
        h->lprev->lnext = m;
        m->lprev = h->lprev;
        h->lprev = m;
        m->lnext = h;
}

/*
 *  Move to head of lru list
 */
void
lruderef(Lru *h, Lru *m)
{
        if(h->lnext == m)
                return;         /* alread at head of list */

        /*
         *  remove from list
         */
        m->lprev->lnext = m->lnext;
        m->lnext->lprev = m->lprev;

        /*
         *  add in at head
         */
        h->lnext->lprev = m;
        m->lnext = h->lnext;
        h->lnext = m;
        m->lprev = h;
}