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/*
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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 sstf_init(sstf_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->lqueue=NULL;
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  q->hqueue=NULL;
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  q->actual=NULL;
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  q->counter=0;
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  return 0;
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}
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int sstf_numelements(sstf_queue_t *q)
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{
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  return q->counter;
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}
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int sstf_insertrequest(sstf_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->actual==NULL)
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    q->actual=e;
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  else {
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    if (e->cylinder<=q->actual->cylinder) {
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      /* insert into low queue */
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      o=NULL;
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      p=q->lqueue;
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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->lqueue=e;
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      else         o->x.next=e;
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      e->x.next=p;
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    } else {
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      /* insert into high queue */
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      o=NULL;
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      p=q->hqueue;
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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->hqueue=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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  }
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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 *sstf_getrequest(sstf_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->actual;
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  __b_fastmutex_unlock(&q->mutex);
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  return ret;
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}
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int sstf_removerequest(sstf_queue_t *q)
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{
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  __b_fastmutex_lock(&q->mutex);
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  assertk(q->actual!=NULL);
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  if (q->lqueue==NULL) {
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    if (q->hqueue==NULL) {
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      /* lqueue==NULL && hqueue==NULL */
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      q->actual=NULL;
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    } else {
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      /* lqueue==NULL && hqueue!=NULL */
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      q->actual=q->hqueue;
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      q->hqueue=q->hqueue->x.next;
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    }
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  } else {
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    if (q->hqueue==NULL) {
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      /* lqueue!=NULL && hqueue==NULL */
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      q->actual=q->lqueue;
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      q->lqueue=q->lqueue->x.next;
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    } else {
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      /* lqueue!=NULL && hqueue!=NULL */
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      int dl,dh;
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      dh=q->hqueue->cylinder-q->actual->cylinder;
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      dl=q->actual->cylinder-q->lqueue->cylinder;
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      if (dh<dl) {
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        q->actual=q->hqueue;
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        q->hqueue=q->hqueue->x.next;
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      } else {
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        q->actual=q->lqueue;
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        q->lqueue=q->lqueue->x.next;    
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      }
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    }
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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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}