util/range.c

   1 /*
   2  * QEMU 64-bit address ranges
   3  *
   4  * Copyright (c) 2015-2016 Red Hat, Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "qemu/osdep.h"
  21 #include "qemu/range.h"
  22
  23 /*
  24  * Return -1 if @a < @b, 1 @a > @b, and 0 if they touch or overlap.
  25  * Both @a and @b must not be empty.
  26  */
  27 static inline int range_compare(Range *a, Range *b)
  28 {
  29     assert(!range_is_empty(a) && !range_is_empty(b));
  30
  31     /* Careful, avoid wraparound */
  32     if (b->lob && b->lob - 1 > a->upb) {
  33         return -1;
  34     }
  35     if (a->lob && a->lob - 1 > b->upb) {
  36         return 1;
  37     }
  38     return 0;
  39 }
  40
  41 /* Insert @data into @list of ranges; caller no longer owns @data */
  42 GList *range_list_insert(GList *list, Range *data)
  43 {
  44     GList *l;
  45
  46     assert(!range_is_empty(data));
  47
  48     /* Skip all list elements strictly less than data */
  49     for (l = list; l && range_compare(l->data, data) < 0; l = l->next) {
  50     }
  51
  52     if (!l || range_compare(l->data, data) > 0) {
  53         /* Rest of the list (if any) is strictly greater than @data */
  54         return g_list_insert_before(list, l, data);
  55     }
  56
  57     /* Current list element overlaps @data, merge the two */
  58     range_extend(l->data, data);
  59     g_free(data);
  60
  61     /* Merge any subsequent list elements that now also overlap */
  62     while (l->next && range_compare(l->data, l->next->data) == 0) {
  63         GList *new_l;
  64
  65         range_extend(l->data, l->next->data);
  66         g_free(l->next->data);
  67         new_l = g_list_delete_link(list, l->next);
  68         assert(new_l == list);
  69     }
  70
  71     return list;
  72 }