util/range.c

/*
 * QEMU 64-bit address ranges
 *
 * Copyright (c) 2015-2016 Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "qemu/osdep.h"
#include "qemu/range.h"

/*
 * Operations on 64 bit address ranges.
 * Notes:
 *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
 *   - this can not represent a full 0 to ~0x0LL range.
 */

/* Return -1 if @a < @b, 1 if greater, and 0 if they touch or overlap. */
static inline int range_compare(Range *a, Range *b)
{
    /* Zero a->end is 2**64, and therefore not less than any b->begin */
    if (a->end && a->end < b->begin) {
        return -1;
    }
    if (b->end && a->begin > b->end) {
        return 1;
    }
    return 0;
}

/* Insert @data into @list of ranges; caller no longer owns @data */
GList *range_list_insert(GList *list, Range *data)
{
    GList *l;

    /* Range lists require no empty ranges */
    assert(data->begin < data->end || (data->begin && !data->end));

    /* Skip all list elements strictly less than data */
    for (l = list; l && range_compare(l->data, data) < 0; l = l->next) {
    }

    if (!l || range_compare(l->data, data) > 0) {
        /* Rest of the list (if any) is strictly greater than @data */
        return g_list_insert_before(list, l, data);
    }

    /* Current list element overlaps @data, merge the two */
    range_extend(l->data, data);
    g_free(data);

    /* Merge any subsequent list elements that now also overlap */
    while (l->next && range_compare(l->data, l->next->data) == 0) {
        GList *new_l;

        range_extend(l->data, l->next->data);
        g_free(l->next->data);
        new_l = g_list_delete_link(list, l->next);
        assert(new_l == list);
    }

    return list;
}