usr/src/sys.386bsd/kern/subr_rlist.c

/*
 * Copyright (c) 1992 William F. Jolitz, TeleMuse
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This software is a component of "386BSD" developed by
        William F. Jolitz, TeleMuse.
 * 4. Neither the name of the developer nor the name "386BSD"
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS A COMPONENT OF 386BSD DEVELOPED BY WILLIAM F. JOLITZ
 * AND IS INTENDED FOR RESEARCH AND EDUCATIONAL PURPOSES ONLY. THIS
 * SOFTWARE SHOULD NOT BE CONSIDERED TO BE A COMMERCIAL PRODUCT.
 * THE DEVELOPER URGES THAT USERS WHO REQUIRE A COMMERCIAL PRODUCT
 * NOT MAKE USE THIS WORK.
 *
 * FOR USERS WHO WISH TO UNDERSTAND THE 386BSD SYSTEM DEVELOPED
 * BY WILLIAM F. JOLITZ, WE RECOMMEND THE USER STUDY WRITTEN
 * REFERENCES SUCH AS THE  "PORTING UNIX TO THE 386" SERIES
 * (BEGINNING JANUARY 1991 "DR. DOBBS JOURNAL", USA AND BEGINNING
 * JUNE 1991 "UNIX MAGAZIN", GERMANY) BY WILLIAM F. JOLITZ AND
 * LYNNE GREER JOLITZ, AS WELL AS OTHER BOOKS ON UNIX AND THE
 * ON-LINE 386BSD USER MANUAL BEFORE USE. A BOOK DISCUSSING THE INTERNALS
 * OF 386BSD ENTITLED "386BSD FROM THE INSIDE OUT" WILL BE AVAILABLE LATE 1992.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPER ``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 DEVELOPER 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.
 *
 */
static char rcsid[] = "$Header: /usr/bill/working/sys/kern/RCS/subr_rlist.c,v 1.2 92/01/21 21:29:31 william Exp $";

#include "sys/param.h"
#include "sys/cdefs.h"
#include "sys/malloc.h"
#include "rlist.h"

/*
 * Resource lists.
 */

/*
 * Add space to a resource list. Used to either
 * initialize a list or return free space to it.
 */
rlist_free (rlp, start, end)
register struct rlist **rlp; unsigned start, end; {
        struct rlist *head;

        head = *rlp;

loop:
        /* if nothing here, insert (tail of list) */
        if (*rlp == 0) {
                *rlp = (struct rlist *)malloc(sizeof(**rlp), M_TEMP, M_NOWAIT);
                (*rlp)->rl_start = start;
                (*rlp)->rl_end = end;
                (*rlp)->rl_next = 0;
                return;
        }

        /* if new region overlaps something currently present, panic */
        if (start >= (*rlp)->rl_start && start <= (*rlp)->rl_end)  {
                printf("Frag %d:%d, ent %d:%d ", start, end,
                        (*rlp)->rl_start, (*rlp)->rl_end);
                panic("overlapping front rlist_free: freed twice?");
        }
        if (end >= (*rlp)->rl_start && end <= (*rlp)->rl_end) {
                printf("Frag %d:%d, ent %d:%d ", start, end,
                        (*rlp)->rl_start, (*rlp)->rl_end);
                panic("overlapping tail rlist_free: freed twice?");
        }

        /* are we adjacent to this element? (in front) */
        if (end+1 == (*rlp)->rl_start) {
                /* coalesce */
                (*rlp)->rl_start = start;
                goto scan;
        }

        /* are we before this element? */
        if (end < (*rlp)->rl_start) {
                register struct rlist *nlp;

                nlp = (struct rlist *)malloc(sizeof(*nlp), M_TEMP, M_NOWAIT);
                nlp->rl_start = start;
                nlp->rl_end = end;
                nlp->rl_next = *rlp;
                *rlp = nlp;
                return;
        }

        /* are we adjacent to this element? (at tail) */
        if ((*rlp)->rl_end + 1 == start) {
                /* coalesce */
                (*rlp)->rl_end = end;
                goto scan;
        }

        /* are we after this element */
        if (start  > (*rlp)->rl_end) {
                rlp = &((*rlp)->rl_next);
                goto loop;
        } else
                panic("rlist_free: can't happen");

scan:
        /* can we coalesce list now that we've filled a void? */
        {
                register struct rlist *lp, *lpn;

                for (lp = head; lp->rl_next ;) {
                        lpn = lp->rl_next;

                        /* coalesce ? */
                        if (lp->rl_end + 1 == lpn->rl_start) {
                                lp->rl_end = lpn->rl_end;
                                lp->rl_next = lpn->rl_next;
                                free(lpn, M_TEMP);
                        } else
                                lp = lp->rl_next;
                }
        }
}

/*
 * Obtain a region of desired size from a resource list.
 * If nothing available of that size, return 0. Otherwise,
 * return a value of 1 and set resource start location with
 * "*loc". (Note: loc can be zero if we don't wish the value)
 */
int rlist_alloc (rlp, size, loc)
struct rlist **rlp; unsigned size, *loc; {
        register struct rlist *lp;


        /* walk list, allocating first thing that's big enough (first fit) */
        for (; *rlp; rlp = &((*rlp)->rl_next))
                if(size <= (*rlp)->rl_end - (*rlp)->rl_start + 1) {

                        /* hand it to the caller */
                        if (loc) *loc = (*rlp)->rl_start;
                        (*rlp)->rl_start += size;

                        /* did we eat this element entirely? */
                        if ((*rlp)->rl_start > (*rlp)->rl_end) {
                                lp = (*rlp)->rl_next;
                                free (*rlp, M_TEMP);
                                *rlp = lp;
                        }

                        return (1);
                }

        /* nothing in list that's big enough */
        return (0);
}

/*
 * Finished with this resource list, reclaim all space and
 * mark it as being empty.
 */
rlist_destroy (rlp)
struct rlist **rlp; {
        struct rlist *lp, *nlp;

        lp = *rlp;
        *rlp = 0;
        for (; lp; lp = nlp) {
                nlp = lp->rl_next;
                free (lp, M_TEMP);
        }
}