Specs

sibling(prefix(), integer()) :: prefix()

Returns another Pfx at distance offset from given pfx.

This basically increases or decreases the number represented by the pfx.bits while keeping pfx.maxlen the same.

Note that the length of pfx.bits will not change and cycling through all siblings will eventually wrap around.

Examples

iex> sibling("1.2.3.0/24", -1)
"1.2.2.0/24"

iex> sibling("0.0.0.0", -1)
"255.255.255.255"

iex> sibling({{1, 2, 3, 0}, 24}, 256)
{{1, 3, 3, 0}, 24}

iex> sibling(%Pfx{bits: <<10, 11>>, maxlen: 32}, 1)
%Pfx{bits: <<10, 12>>, maxlen: 32}

iex> sibling(%Pfx{bits: <<10, 11, 0>>, maxlen: 32}, 255)
%Pfx{bits: <<10, 11, 255>>, maxlen: 32}

# wraps around
iex> sibling(%Pfx{bits: <<10, 11, 0>>, maxlen: 32}, 256)
%Pfx{bits: <<10, 12, 0>>, maxlen: 32}

iex> new(<<0, 0, 0, 0>>, 32) |> sibling(-1)
%Pfx{bits: <<255, 255, 255, 255>>, maxlen: 32}

# zero bit-length stays zero bit-length
iex> sibling(%Pfx{bits: <<>>, maxlen: 0}, 1)
%Pfx{bits: <<>>, maxlen: 0}