This returns a population count of all the bits that are set in the
bitmask.
There is now also a _cogl_bitmask_popcount_upto which counts the
number of bits set up to but not including the given bit index. This
will be useful to determine the number of uniform overrides to skip if
we tightly pack the values in an array.
The test-bitmask test has been modified to check these two functions.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
Instead of testing each bit when iterating a bitmask, we can use ffsl
to skip over unset bits in single instruction. That way it will scale
by the number of bits set, not the total number of bits.
ffsl is a non-standard function which glibc only provides by defining
GNUC_SOURCE. However if we are compiling with GCC we can avoid that
mess and just use the equivalent builtin. When not compiling for GCC
it will fall back to _cogl_util_ffs if the size of ints and longs are
the same (which is the case on i686). Otherwise it fallbacks to a slow
function implementation.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This adds a test which tries manipulating some bits on a CoglBitmask
and verifies that it gets the expected result. This test is fairly
unusual in that it is directly testing some internal Cogl code that
isn't exposed through the public API. To make this work it directly
includes the source for CoglBitmask.
CoglBitmask does some somewhat dodgy things with converting longs to
pointers and back so it makes sense to have a test case to verify that
this is working on all platforms.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
