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bitfield

1.0.0
1.0.0

Simple bitfields for erlang/elixir

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bitfield src bitfield.erl
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src/bitfield.erl 

-module(bitfield).



-export([pack/2]).

-export([unpack/2]).



-spec pack(list(), list()) -> binary().

pack(Enabled, Enum) when is_list(Enabled) andalso is_list(Enum) ->

  pack(gb_sets:from_list(Enabled), Enum, <<>>).

pack(_, [], Acc) ->

  fill(Acc);

pack(Enabled, [Field|Enum], Acc) ->

  Acc2 = case gb_sets:is_member(Field, Enabled) of

    true -> <<Acc/bitstring, 1:1>>;

    _ -> <<Acc/bitstring, 0:1>>

  end,

  pack(Enabled, Enum, Acc2).



-spec unpack(binary(), list()) -> list().

unpack(Packed, Enum) when is_binary(Packed) andalso is_list(Enum) ->

  unpack(Packed, Enum, []).

unpack(_, [], Acc) ->

  lists:reverse(Acc);

unpack(<<>>, _, Acc) ->

  lists:reverse(Acc);

unpack(<<1:1/little-unsigned, Packed/bitstring>>, [Field|Enum], Acc) ->

  unpack(Packed, Enum, [Field|Acc]);

unpack(<<0:1/little-unsigned, Packed/bitstring>>, [_|Enum], Acc) ->

  unpack(Packed, Enum, Acc).



fill(Bitstring) ->

  Len = 8 - bit_size(Bitstring) rem 8,

  <<Bitstring/bitstring, 0:Len>>.