Rewrite logic in vlen
to drop NumPy build dependency
#555
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As noted in issue ( https://github.com/zarr-developers/numcodecs ),
vlen
had problems with read-only dataInternally this occurred because we assigned the input array to
object[:]
, which expects mutability. Ideally we would just replace this withconst object[:]
. However Cython does not support this ( cython/cython#2485 ). Over time various blockers have been resolved on that front, but it is not yet fixedFortunately an astute SciPy developer noted that
const <fused_type>[:]
is allowed ( scipy/scipy#18192 (review) ). We use that same trick hereThis in turn should allow us to continue to accept read-only arrays. Though this does so without a NumPy build dependency, which can introduce more complexity to the build process
TODO: