Accessor
Allows reading another file by overlaying a sparse map on top of it.
The map excludes reading from certain areas which are considered sparse.
The resulting file is sparse (and therefore uploading it excludes the masked out regions). The filename is taken as a list of ranges.
For example here we create a sparse file over the delegate which only defines the first 5 bytes, then a 5 byte sparse region then another 5 bytes.
SELECT upload(accessor="sparse", path=pathspec(
DelegateAccessor="data", DelegatePath=MyData,
Path=[dict(Offset=0,Length=5), dict(Offset=10,Length=5)])
FROM scope()
The uploaded file will contain only 10 bytes but will retain the 5 byte “hole” in the middle.
This accessor is most useful when uploading or masking parts of other files - for example uploading a carved files from a larger image. Note that delegate offsets are retained in this accessor (so for example offset 10 in this accessor corresponds to offset 10 in the delegate regardless of the sparse map).
For more flexibility than this use the “ranged” accessor.