1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
"""
A `DataCallback` class is implemented here to allow
for reassignment of the index of an ASDF block corresponding
to a callback.
This is needed so that extension code can generate a callback
during deserialization of an ASDF file that will continue
to be valid even after an `AsdfFile.update` which might
reorder blocks.
To allow for 'low-level' block access needed for ndarray
`DataCallback` can be called with an optional ``_attr``
argument to cache data, access the block header and other
operations that we generally do not want to expose to
extension code.
"""
import weakref
class DataCallback:
"""
A callable object used to read data from an ASDF block
read from an ASDF file.
"""
def __init__(self, index, read_blocks):
self._reassign(index, read_blocks)
def __call__(self, _attr=None):
read_blocks = self._read_blocks_ref()
if read_blocks is None:
msg = "Attempt to read block data from missing block"
raise OSError(msg)
if _attr is None:
return read_blocks[self._index].data
else:
# _attr allows NDArrayType to have low level block access for things
# like reading the header and cached_data
return getattr(read_blocks[self._index], _attr)
def _reassign(self, index, read_blocks):
self._index = index
self._read_blocks_ref = weakref.ref(read_blocks)
|
