Use memoryview.itemsize if no default provided

[mrocklin]

If I give blosc.compress a memoryview object it would be possible to learn the typesize automatically.

In [1]: import numpy as np

In [2]: x = np.ones(5, dtype='i4')

In [3]: x.data
Out[3]: <memory at 0x7fe710bf0408>

In [4]: x.data.itemsize
Out[4]: 4

In [5]: import blosc

In [6]: blosc.compress(x.data, typesize=x.data.itemsize)
Out[6]: b'\x02\x01\x13\x04\x14\x00\x00\x00\x14\x00\x00\x00$\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00'

[esc]

If you think that is useful, pull-requests will be accepted. :+1:

[esc]

@mrocklin I would implement this next perhaps, will it still be of value to you?

[mrocklin]

Not of concrete value, no. I specify this myself. I think it is a sensible default for the project though.

[FrancescAlted]

Closing after no activity for long time. FWIW, there is full support for views and objects supporting the buffer protocol in next-generation python-blosc2.