/*
 * (MPSAFE)
 *
 * Copyright (c) 1999 Michael Smith <msmith@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/kern/subr_eventhandler.c,v 1.3 1999/11/16 16:28:57 phk Exp $
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/systm.h>
#include <sys/eventhandler.h>

MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");

/* List of 'slow' lists */
static TAILQ_HEAD(, eventhandler_list)  eventhandler_lists = TAILQ_HEAD_INITIALIZER(eventhandler_lists);
static struct lwkt_token evlist_token = LWKT_TOKEN_INITIALIZER(evlist_token);

struct eventhandler_entry_generic 
{
    struct eventhandler_entry   ee;
    void                        (* func)(void);
};

/* 
 * Insertion is O(n) due to the priority scan, but optimises to O(1)
 * if all priorities are identical.
 *
 * MPSAFE
 */
eventhandler_tag
eventhandler_register(struct eventhandler_list *list, const char *name, 
                      void *func, void *arg, int priority)
{
    struct eventhandler_entry_generic   *eg;
    struct eventhandler_entry           *ep;
    
    lwkt_gettoken(&evlist_token);

    /*
     * find/create the list as needed
     */
    while (list == NULL) {
        list = eventhandler_find_list(name);
        if (list)
                break;
        list = kmalloc(sizeof(struct eventhandler_list) + strlen(name) + 1,
                       M_EVENTHANDLER, M_INTWAIT);
        if (eventhandler_find_list(name)) {
            kfree(list, M_EVENTHANDLER);
            list = NULL;
        } else {
            list->el_flags = 0;
            list->el_name = (char *)list + sizeof(struct eventhandler_list);
            strcpy(list->el_name, name);
            TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
        }
    }

    if (!(list->el_flags & EHE_INITTED)) {
        TAILQ_INIT(&list->el_entries);
        list->el_flags = EHE_INITTED;
    }
    
    /* allocate an entry for this handler, populate it */
    eg = kmalloc(sizeof(struct eventhandler_entry_generic),
                M_EVENTHANDLER, M_INTWAIT);
    eg->func = func;
    eg->ee.ee_arg = arg;
    eg->ee.ee_priority = priority;
    
    /* sort it into the list */
    for (ep = TAILQ_FIRST(&list->el_entries);
         ep != NULL; 
         ep = TAILQ_NEXT(ep, ee_link)) {
        if (eg->ee.ee_priority < ep->ee_priority) {
            TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
            break;
        }
    }
    if (ep == NULL)
        TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
    lwkt_reltoken(&evlist_token);

    return(&eg->ee);
}

/*
 * MPSAFE
 */
void
eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
{
    struct eventhandler_entry   *ep = tag;

    lwkt_gettoken(&evlist_token);
    /* XXX insert diagnostic check here? */

    if (ep != NULL) {
        /* remove just this entry */
        TAILQ_REMOVE(&list->el_entries, ep, ee_link);
        kfree(ep, M_EVENTHANDLER);
    } else {
        /* remove entire list */
        while (!TAILQ_EMPTY(&list->el_entries)) {
            ep = TAILQ_FIRST(&list->el_entries);
            TAILQ_REMOVE(&list->el_entries, ep, ee_link);
            kfree(ep, M_EVENTHANDLER);
        }
    }
    lwkt_reltoken(&evlist_token);
}

/*
 * Locate the requested list
 */
struct eventhandler_list *
eventhandler_find_list(const char *name)
{
    struct eventhandler_list    *list;

    lwkt_gettoken(&evlist_token);
    for (list = TAILQ_FIRST(&eventhandler_lists); 
         list != NULL; 
         list = TAILQ_NEXT(list, el_link)) {
        if (!strcmp(name, list->el_name))
            break;
    }
    lwkt_reltoken(&evlist_token);
    return(list);
}