Specs

member(prefix(), integer()) :: prefix()

Returns the nth-member of a given pfx.

A prefix represents a range of (possibly longer) prefixes which can be seen as members of the prefix. So a prefix of n-bits long represents:

• 1 prefix of n-bits long (i.e. itself),
• 2 prefixes of n+1-bits long,
• 4 prefixes of n+2-bits long
• ..
• 2^w prefixes of n+w-bits long

where n+w <= pfx.maxlen.

Not specifying a width assumes the maximum width available. If a width is specified, the nth-offset is added to the prefix as a number width-bits wide. This wraps around the available address space.

Examples

iex> member("10.10.10.0/24", 255)
"10.10.10.255"

# wraps around
iex> member("10.10.10.0/24", 256)
"10.10.10.0"

iex> member({{10, 10, 10, 0}, 24}, 255)
{{10, 10, 10, 255}, 32}

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

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

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

iex> member(%Pfx{bits: <<10, 10, 10>>, maxlen: 32}, -1)
%Pfx{bits: <<10, 10, 10, 255>>, maxlen: 32}

# a full prefix always returns itself
iex> member(%Pfx{bits: <<10, 10, 10, 10>>, maxlen: 32}, 0)
%Pfx{bits: <<10, 10, 10, 10>>, maxlen: 32}

iex> member(%Pfx{bits: <<10, 10, 10, 10>>, maxlen: 32}, 3)
%Pfx{bits: <<10, 10, 10, 10>>, maxlen: 32}

Specs

member(prefix(), integer(), pos_integer()) :: prefix()

Returns the nth member in the set represented by pfx, using width bits.

Examples

iex> member("10.10.10.0/24", 1, 2)
"10.10.10.64/26"

iex> member("10.10.10.0/24", 2, 2)
"10.10.10.128/26"

iex> member({{10, 10, 10, 0}, 24}, 2, 2)
{{10, 10, 10, 128}, 26}

# the first member that is 2 bits longer
iex> member(%Pfx{bits: <<10, 10, 10>>, maxlen: 32}, 0, 2)
%Pfx{bits: <<10, 10, 10, 0::2>>, maxlen: 32}

# the second member that is 2 bits longer
iex> member(%Pfx{bits: <<10, 10, 10>>, maxlen: 32}, 1, 2)
%Pfx{bits: <<10, 10, 10, 1::2>>, maxlen: 32}