Allow bytearray as input

[Downchuck]

Currently the bytes_to_slice does not support bytearray; bytearray is just a standard/compatible pointer.

batch.put(key, bytearray("data"))

[Downchuck]

Possibly related:
https://github.com/cython/cython/blob/master/Cython/Includes/cpython/bytes.pxd#L77

Seems to suggest that arbitrary binary data would be converted to Unicode.
EDIT: Doesn't seem to be an issue. Still, it seems that a direct cast to char* would work fine.

[Downchuck]

Not sure how safe it is, but this lets me pass in bytearray:

+++ b/rocksdb/_rocksdb.pyx
 cdef Slice bytes_to_slice(ob) except *:
-    return Slice(PyBytes_AsString(ob), PyBytes_Size(ob))
+    return Slice(<char*>ob, len(ob))

[Downchuck]

@stephan-hof What are your thoughts on this one?
You could do an if(isinstance(ob, bytearray)) to support it.

[stephan-hof]

Hi @Downchuck I think its a good idea to support byte-array (and possibly memoryview, buffer, ...).
I have also seen that you opened/commented on other issues, so I guess you are currently working with the stuff.
Unfortunately I'm currently super busy with other things, so I don't have much time to dive into the issues right now. I'll have a look at them end of next week.

[Downchuck]

I tried to support memoryview in another cython project -- I did not succeed.

bytearray was easy, as it was just a raw char*. It seems like memoryview and buffer both need their own work, futher, I was trying to pass a memoryviewslice from another cython build (via runcython).

Anyway, that single-line item seems to handle python bytes() and bytearray().