table-based version from LZMA SDK 4.57. This should be
fast on most systems.
A simpler and smaller alternative version is also provided.
On some CPUs this can be even a little faster than the
default table-based version (see comments in fastpos.h),
but on most systems the table-based code is faster.
coder->lz.stream_end_was_reached. That variable
will be removed, and the check isn't required anyway.
Rearrange the check so that it doesn't make one to
think that there could be an integer overflow.
