util/range.c

   1 /*
   2  * QEMU 64-bit address ranges
   3  *
   4  * Copyright (c) 2015-2016 Red Hat, Inc.
   5  *
   6  * This library 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 library 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  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  */
  20
  21 #include "qemu/osdep.h"
  22 #include "qemu/range.h"
  23
  24 /*
  25  * Operations on 64 bit address ranges.
  26  * Notes:
  27  *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
  28  *   - this can not represent a full 0 to ~0x0LL range.
  29  */
  30
  31 /* Return -1 if @a < @b, 1 if greater, and 0 if they touch or overlap. */
  32 static inline int range_compare(Range *a, Range *b)
  33 {
  34     /* Zero a->end is 2**64, and therefore not less than any b->begin */
  35     if (a->end && a->end < b->begin) {
  36         return -1;
  37     }
  38     if (b->end && a->begin > b->end) {
  39         return 1;
  40     }
  41     return 0;
  42 }
  43
  44 /* Insert @data into @list of ranges; caller no longer owns @data */
  45 GList *range_list_insert(GList *list, Range *data)
  46 {
  47     GList *l;
  48
  49     /* Range lists require no empty ranges */
  50     assert(data->begin < data->end || (data->begin && !data->end));
  51
  52     /* Skip all list elements strictly less than data */
  53     for (l = list; l && range_compare(l->data, data) < 0; l = l->next) {
  54     }
  55
  56     if (!l || range_compare(l->data, data) > 0) {
  57         /* Rest of the list (if any) is strictly greater than @data */
  58         return g_list_insert_before(list, l, data);
  59     }
  60
  61     /* Current list element overlaps @data, merge the two */
  62     range_extend(l->data, data);
  63     g_free(data);
  64
  65     /* Merge any subsequent list elements that now also overlap */
  66     while (l->next && range_compare(l->data, l->next->data) == 0) {
  67         GList *new_l;
  68
  69         range_extend(l->data, l->next->data);
  70         g_free(l->next->data);
  71         new_l = g_list_delete_link(list, l->next);
  72         assert(new_l == list);
  73     }
  74
  75     return list;
  76 }