Maps FUSE file handles (fh, a UInt64) to arbitrary open-file state of
type T. Handles are minted from a monotonically increasing counter
starting at 1 (0 is left as a "no handle" sentinel).
Instance methods
[](fh : UInt64) : T
The value for fh, or raise (KeyError) if unknown.
[]?(fh : UInt64) : T | Nil
The value for fh, or nil if unknown.
add(value : T) : UInt64
Register value and return a fresh handle for it.
delete(fh : UInt64) : T | Nil
Forget fh, returning the value it held (or nil).
size
Number of currently-open handles.