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/*
 * Copyright (C) 2005 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
 */

#include <mm/buddy.h>
#include <mm/frame.h>
#include <mm/heap.h>
#include <arch/types.h>
#include <typedefs.h>
#include <list.h>
#include <debug.h>

/** Create buddy system
 *
 * Allocate memory for and initialize new buddy system.
 *
 * @param max_order The biggest allocable size will be 2^max_order.
 * @param op Operations for new buddy system.
 * @param data Pointer to be used by implementation.
 *
 * @return New buddy system.
 */
buddy_system_t *buddy_system_create(__u8 max_order, buddy_system_operations_t *op, void *data)
{
    buddy_system_t *b;
    int i;

    ASSERT(max_order < BUDDY_SYSTEM_INNER_BLOCK);

    ASSERT(op->find_buddy);
    ASSERT(op->set_order);
    ASSERT(op->get_order);
    ASSERT(op->bisect);
    ASSERT(op->coalesce);

    /*
     * Allocate memory for structure describing the whole buddy system.
     */ 
    b = (buddy_system_t *) early_malloc(sizeof(buddy_system_t));
    
    if (b) {
        /*
         * Allocate memory for all orders this buddy system will work with.
         */
        b->order = (link_t *) early_malloc(max_order * sizeof(link_t));
        if (!b->order) {
            early_free(b);
            return NULL;
        }
    
        for (i = 0; i < max_order; i++)
            list_initialize(&b->order[i]);
    
        b->max_order = max_order;
        b->op = op;
        b->data = data;
    }
    
    return b;
}

/** Allocate block from buddy system.
 *
 * @param b Buddy system pointer.
 * @param i Returned block will be 2^i big.
 *
 * @return Block of data represented by link_t.
 */
link_t *buddy_system_alloc(buddy_system_t *b, __u8 i)
{
    link_t *res, *hlp;

    ASSERT(i < b->max_order);

    /*
     * If the list of order i is not empty,
     * the request can be immediatelly satisfied.
     */
    if (!list_empty(&b->order[i])) {
        res = b->order[i].next;
        list_remove(res);
        return res;
    }
    
    /*
     * If order i is already the maximal order,
     * the request cannot be satisfied.
     */
    if (i == b->max_order - 1)
        return NULL;

    /*
     * Try to recursively satisfy the request from higher order lists.
     */ 
    hlp = buddy_system_alloc(b, i + 1);
    
    /*
     * The request could not be satisfied
     * from higher order lists.
     */
    if (!hlp)
        return NULL;
        
    res = hlp;
    
    /*
     * Bisect the block and set order of both of its parts to i.
     */
    hlp = b->op->bisect(b, res);
    b->op->set_order(b, res, i);
    b->op->set_order(b, hlp, i);
    
    /*
     * Return the other half to buddy system.
     */
    buddy_system_free(b, hlp);
    
    return res;
    
}

/** Return block to buddy system.
 *
 * @param b Buddy system pointer.
 * @param block Block to return.
 */
void buddy_system_free(buddy_system_t *b, link_t *block)
{
    link_t *buddy, *hlp;
    __u8 i;
    
    /*
     * Determine block's order.
     */
    i = b->op->get_order(b, block);

    ASSERT(i < b->max_order);

    if (i != b->max_order - 1) {
        /*
         * See if there is any buddy in the list of order i.
         */
        buddy = b->op->find_buddy(b, block);
        if (buddy) {

            ASSERT(b->op->get_order(b, buddy) == i);
        
            /*
             * Remove buddy from the list of order i.
             */
            list_remove(buddy);
        
            /*
             * Invalidate order of both block and buddy.
             */
            b->op->set_order(b, block, BUDDY_SYSTEM_INNER_BLOCK);
            b->op->set_order(b, buddy, BUDDY_SYSTEM_INNER_BLOCK);
        
            /*
             * Coalesce block and buddy into one block.
             */
            hlp = b->op->coalesce(b, block, buddy);

            /*
             * Set order of the coalesced block to i + 1.
             */
            b->op->set_order(b, hlp, i + 1);

            /*
             * Recursively add the coalesced block to the list of order i + 1.
             */
            buddy_system_free(b, hlp);
            return;
        }
    }

    /*
     * Insert block into the list of order i.
     */
    list_append(block, &b->order[i]);

}