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author | Markus Armbruster <armbru@redhat.com> | 2016-07-01 13:47:48 +0200 |
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committer | Michael S. Tsirkin <mst@redhat.com> | 2016-07-04 16:49:33 +0300 |
commit | 6dd726a2bf1b800289d90a84d5fcb5ce7b78a8e1 (patch) | |
tree | 8c201b1c334e3eca5b857a7d7541b5407c229733 /util | |
parent | a0efbf16604770b9d805bcf210ec29942321134f (diff) | |
download | qemu-6dd726a2bf1b800289d90a84d5fcb5ce7b78a8e1.zip qemu-6dd726a2bf1b800289d90a84d5fcb5ce7b78a8e1.tar.gz qemu-6dd726a2bf1b800289d90a84d5fcb5ce7b78a8e1.tar.bz2 |
range: Replace internal representation of Range
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>
Diffstat (limited to 'util')
-rw-r--r-- | util/range.c | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/util/range.c b/util/range.c index e5f2e71..416df7c 100644 --- a/util/range.c +++ b/util/range.c @@ -22,20 +22,18 @@ #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 @a > @b, and 0 if they touch or overlap. + * Both @a and @b must not be empty. */ - -/* 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) { + assert(!range_is_empty(a) && !range_is_empty(b)); + + /* Careful, avoid wraparound */ + if (b->lob && b->lob - 1 > a->upb) { return -1; } - if (b->end && a->begin > b->end) { + if (a->lob && a->lob - 1 > b->upb) { return 1; } return 0; |