/* Copyright 1992 Carnegie Mellon University, All rights reserved.
 $Disclaimer: 
 * Permission to use, copy, modify, and distribute this software and its 
 * documentation for any purpose is hereby granted without fee, 
 * provided that the above copyright notice appear in all copies and that 
 * both that copyright notice, this permission notice, and the following 
 * disclaimer appear in supporting documentation, and that the names of 
 * IBM, Carnegie Mellon University, and other copyright holders, not be 
 * used in advertising or publicity pertaining to distribution of the software 
 * without specific, written prior permission.
 * 
 * IBM, CARNEGIE MELLON UNIVERSITY, AND THE OTHER COPYRIGHT HOLDERS 
 * DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 
 * ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.  IN NO EVENT 
 * SHALL IBM, CARNEGIE MELLON UNIVERSITY, OR ANY OTHER COPYRIGHT HOLDER 
 * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY 
 * DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, 
 * WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 *  $
 */
/* $Header: /afs/cs.cmu.edu/project/atk-dist/auis-6.3/atk/basics/common/RCS/owatch.c,v 1.3 1993/01/25 16:07:34 rr2b Exp $ */

#ifndef NORCSID
char *owatch_c_rcsid = "$Header: /afs/cs.cmu.edu/project/atk-dist/auis-6.3/atk/basics/common/RCS/owatch.c,v 1.3 1993/01/25 16:07:34 rr2b Exp $";
#endif

#include <andrewos.h>
#include <class.h>

#include <observe.ih>
#include "owatch.eh"

static struct owatch_data *freedata=NULL;
static struct owatch_data *useddata=NULL;
static struct owatch *owo=NULL;

#define owatch_BLOCKSIZE 8160
#define owatch_WATCHESPERBLOCK (owatch_BLOCKSIZE/sizeof(struct owatch_data))

void owatch__ObservedChanged(self, changed, value)
struct owatch *self;
struct observable *changed;
long value;  {
    struct owatch_data *o=useddata;
    if(value!=observable_OBJECTDESTROYED) return;
    while(o) {
	if(o->obj==changed && o->alive) {
	    o->alive=FALSE;
	    return;
	}
	o=o->next;
    }
}

struct owatch_data *owatch__Create(classID, obj)
struct classheader *classID;
struct observable *obj;
{
    int i;
    struct owatch_data *o=useddata;
    if(obj==NULL) return NULL;
    
    if(owo==NULL) {
	owo=owatch_New();
	if(owo==NULL) return NULL;
    }
    
    while(o) {
	if(o->obj==obj && o->alive) {
	    o->refs++;
	    return o;
	}
	o=o->next;
    }
    if(freedata==NULL) {
	struct owatch_data *oarray;
	oarray=(struct owatch_data *)malloc(owatch_WATCHESPERBLOCK*sizeof(struct owatch_data));
	if(oarray==NULL) return NULL;
	for(i=0;i<owatch_WATCHESPERBLOCK-1;i++) {
	    oarray[i].refs=0;
	    oarray[i].obj=NULL;
	    oarray[i].alive=FALSE;
	    oarray[i].next=oarray+i+1;
	    oarray[i].prev=oarray+i-1;
	}
	oarray[0].prev=NULL;
	oarray[owatch_WATCHESPERBLOCK-1].next=NULL;
	freedata=oarray;
    }
    if(freedata==NULL) return NULL;
    o=freedata;
    freedata=freedata->next;
    o->obj=obj;
    o->alive=TRUE;
    o->next=useddata;
    o->prev=NULL;
    o->refs++;
    if(useddata) {
	useddata->prev=o;
    }
    useddata=o;
    observable_AddObserver(o->obj, owo);
    return o;
}

void owatch__Delete(classID, owd)
struct classheader *classID;
struct owatch_data *owd;
{
    if(owd==NULL) return;
    if(owd->refs<1) {
	fprintf(stderr, "owatch: Attempt to delete an already free owatch_data structure.");
	return;
    }
    if(--(owd->refs)>0) return;
    if(owd->alive) {
	observable_RemoveObserver(owd->obj, owo);
    }
    if(owd->next) owd->next->prev=owd->prev;
    if(owd->prev) owd->prev->next=owd->next;
    else useddata=owd->next;
    owd->next=freedata;
    owd->prev=NULL;
    freedata=owd;
}

boolean owatch__CheckAndDelete(classID, owd)
struct classheader *classID;
struct owatch_data *owd;
{
    boolean result;
    if(owd==NULL) return FALSE;
    result=owatch_Check(owd);
    owatch_Delete(owd);
    return result;
}