Fast implementation for dealing with immutable bitarray sets.
Add ExBitset to your mix.exs
dependencies:
def deps do
[
{:ex_bitset, "~> 0.1.0"}
]
end
To define a bitset type you need to use the defbitset
function inside the
Elixir module (similar to how you would define structs).
defmodule Roles do
import ExBitset, only: [defbitset: 1]
defbitset [:admin, :owner, :writer, :viewer, :guest]
end
You can then create new bitsets using the previously defined structure and perform operations on it:
roles = ExBitset.new(Roles, [:admin, :owner])
assert Enum.member?(roles, :admin)
assert :owner in Enum.to_list(roles)
bin_roles = ExBitset.to_binary(roles)
int_roles = ExBitset.to_int(roles)
assert Roles
|> ExBitset.from_binary(bin_roles)
|> Enum.member?(:admin)
assert Roles
|> ExBitset.from_int(int_roles)
|> Enum.member?(:admin)
To store one of these bitsets on the DB using, you can define a new Ecto type. The type being stored can be an integer or binary, we're going to use integer in this example because it would be more efficient for small sets, but you could use any.
defmodule MyApp.EctoTypes.Roles do
import ExBitset, only: [defbitset: 1]
use Ecto.Type
defbitset [:admin, :owner, :writer, :viewer, :guest]
def type, do: :integer
def cast(roles) when is_list(roles) do
{:ok, ExBitset.new(__MODULE__, roles)}
end
def cast(roles) when is_struct(roles, ExBitset) do
{:ok, roles}
end
def cast(_roles), do: :error
def load(roles) when is_integer(roles) do
{:ok, ExBitset.from_int(__MODULE__, roles)}
end
def dump(roles) when is_struct(roles, ExBitset) do
{:ok, ExBitset.to_int(roles)}
end
def dump(_roles), do: :error
end