Hi,

Very good idea. However, you don't need to discriminate for the bytes
type specifically. When a buffer is taken on the object (with
PyObject_GetBuffer()), the object is internally "locked" until the
buffer is release with PyBuffer_Release(). Try with a bytearray and
you'll see: if you resize the bytearray while hashing it in another
thread, you'll get a BufferError exception.

All in all, it should make your code and macros much simpler.