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Range represents a range as follows. Member @start is the inclusive lower bound, member @end is the exclusive upper bound. Zero @end is special: if @start is also zero, the range is empty, else @end is to be interpreted as 2^64. No other empty ranges may occur. The range [0,2^64-1] cannot be represented. If you try to create it with range_set_bounds1(), you get the empty range instead. If you try to create it with range_set_bounds() or range_extend(), assertions fail. Before range_set_bounds() existed, the open-coded creation usually got you the empty range instead. Open deathtrap. Moreover, the code dealing with the janus-faced @end is too clever by half. Dumb this down to a more pedestrian representation: members @lob and @upb are inclusive lower and upper bounds. The empty range is encoded as @lob = 1, @upb = 0. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
74 lines
2.1 KiB
C
74 lines
2.1 KiB
C
/*
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* QEMU 64-bit address ranges
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*
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* Copyright (c) 2015-2016 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "qemu/osdep.h"
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#include "qemu/range.h"
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/*
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* Return -1 if @a < @b, 1 @a > @b, and 0 if they touch or overlap.
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* Both @a and @b must not be empty.
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*/
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static inline int range_compare(Range *a, Range *b)
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{
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assert(!range_is_empty(a) && !range_is_empty(b));
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/* Careful, avoid wraparound */
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if (b->lob && b->lob - 1 > a->upb) {
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return -1;
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}
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if (a->lob && a->lob - 1 > b->upb) {
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return 1;
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}
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return 0;
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}
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/* Insert @data into @list of ranges; caller no longer owns @data */
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GList *range_list_insert(GList *list, Range *data)
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{
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GList *l;
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assert(!range_is_empty(data));
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/* Skip all list elements strictly less than data */
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for (l = list; l && range_compare(l->data, data) < 0; l = l->next) {
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}
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if (!l || range_compare(l->data, data) > 0) {
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/* Rest of the list (if any) is strictly greater than @data */
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return g_list_insert_before(list, l, data);
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}
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/* Current list element overlaps @data, merge the two */
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range_extend(l->data, data);
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g_free(data);
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/* Merge any subsequent list elements that now also overlap */
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while (l->next && range_compare(l->data, l->next->data) == 0) {
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GList *new_l;
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range_extend(l->data, l->next->data);
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g_free(l->next->data);
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new_l = g_list_delete_link(list, l->next);
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assert(new_l == list);
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}
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return list;
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}
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