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/openbmc/qemu/util/
H A Drange.cdiff 6dd726a2bf1b800289d90a84d5fcb5ce7b78a8e1 Fri Jul 01 06:47:48 CDT 2016 Markus Armbruster <armbru@redhat.com> 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>
/openbmc/qemu/include/qemu/
H A Drange.hdiff 6dd726a2bf1b800289d90a84d5fcb5ce7b78a8e1 Fri Jul 01 06:47:48 CDT 2016 Markus Armbruster <armbru@redhat.com> 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>