FFI Fails to Account For Offsets #3671

Describe the bug

Passing an ffi::ArrowArray with a non-zero offset, results in an ArrayData with Buffer with truncated lengths, as it assumes they have no offset when recording their length.

This is the cause of #3646

To Reproduce

Expected behavior

Sliced arrays should round-trip through FFI

Additional context

I don't think this can result in UB, it just results in bounds checks failing when they shouldn't