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2 pj 1
/*
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 * Project: S.Ha.R.K.
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 *
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 * Coordinators:
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 *   Giorgio Buttazzo    <giorgio@sssup.it>
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 *   Paolo Gai           <pj@gandalf.sssup.it>
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 *
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 * Authors     :
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 *   Paolo Gai           <pj@gandalf.sssup.it>
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 *   Massimiliano Giorgi <massy@gandalf.sssup.it>
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 *   Luca Abeni          <luca@gandalf.sssup.it>
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 *   (see the web pages for full authors list)
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 *
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 * ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy)
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 *
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 * http://www.sssup.it
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 * http://retis.sssup.it
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 * http://shark.sssup.it
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 */
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/*
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 * Copyright (C) 2000 Massimiliano Giorgi
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 *
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 *
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 */
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#include "bqueue.h"
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#include "glue.h"
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int clook_init(clook_queue_t *q)
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{
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  __b_fastmutex_init(&q->mutex);
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  q->disk=NULL;
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  q->queue[0]=NULL;
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  q->queue[1]=NULL;
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  q->act=0;
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  q->counter=0;
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  return 0;
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}
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int clook_numelements(clook_queue_t *q)
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{
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  return q->counter;
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}
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/* 0 -> no starvation */
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/* 1 -> possible starvation */
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#define STARVATION 0
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int clook_insertrequest(clook_queue_t *q, request_prologue_t *e)
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{
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  request_prologue_t *p,*o;
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  __b_fastmutex_lock(&q->mutex);
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  if (q->queue[q->act]==NULL) {
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    q->queue[q->act]=e;
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    e->x.next=NULL;
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  } else if (e->cylinder>q->queue[q->act]->cylinder-STARVATION) {
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    o=q->queue[q->act];
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    p=o->x.next;
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    while (p!=NULL) {
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      if (e->cylinder<p->cylinder) break;
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      o=p;
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      p=p->x.next;
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    }
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    o->x.next=e;
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    e->x.next=p;    
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  } else {
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    o=NULL;
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    p=q->queue[q->act^1];
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    while (p!=NULL) {
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      if (e->cylinder<p->cylinder) break;
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      o=p;
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      p=p->x.next;
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    }
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    if (o==NULL) q->queue[q->act^1]=e;
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    else         o->x.next=e;
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    e->x.next=p;
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  }
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  q->counter++;
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  __b_fastmutex_unlock(&q->mutex);  
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  return 0;
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}
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request_prologue_t *clook_getrequest(clook_queue_t *q)
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{
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  request_prologue_t *ret;
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  __b_fastmutex_lock(&q->mutex);
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  ret=q->queue[q->act];
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  if (ret==NULL) {
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    q->act^=1;
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    ret=q->queue[q->act];
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  }
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  __b_fastmutex_unlock(&q->mutex);
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  return ret;
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}
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int clook_removerequest(clook_queue_t *q)
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{
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  __b_fastmutex_lock(&q->mutex);
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  assertk(q->queue[q->act]!=NULL);
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  q->queue[q->act]=q->queue[q->act]->x.next;
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  q->counter--;
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  __b_fastmutex_unlock(&q->mutex);  
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  return 0;
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}