Decode of partial erlang external term format

decode.erl

-module(decode).

-export([term/1]).

term(<<131,Rest/binary>>) ->
    element(1,term(Rest));
%% List
term(<<108,Sz:32,Rest/binary>>) ->
    {Lst, R} = lists:foldl(
                 fun(_, {Acc, B}) ->
                         {H, LRest} = term(B),
                         {[H|Acc], LRest}
                 end, {[],Rest}, lists:seq(1,Sz)),
    {Tl, MR} = term(R),
    {lists:reverse(Lst,Tl), MR};
%% Tuple
term(<<104,Sz,Rest/binary>>) ->
    {Lst, R} = lists:foldl(
                 fun(_, {Acc, B}) ->
                         {H, LRest} = term(B),
                         {[H|Acc], LRest}
                 end, {[],Rest}, lists:seq(1,Sz)),
    {list_to_tuple(lists:reverse(Lst)), R};
%% map
term(<<116,Sz:32,Rest/binary>>) ->
    {_Lst, Lst, R} = lists:foldl(
                       fun F(A, {[V,K], M, B}) ->
                               F(A,{[], [{K,V}|M], B});
                           F(_, {Acc, M, B}) ->
                               {H, LRest} = term(B),
                               {[H|Acc], M, LRest}
                       end, {[],[],Rest}, lists:seq(1,Sz*2)),
    {maps:from_list(Lst), R};
%% big
term(<<110, Sz, Sign, Num:Sz/binary, Rest/binary>>) ->
    Big = lists:sum([D * (1 bsl N) || {D, N} <- lists:zip(binary_to_list(Num), lists:seq(0,Sz-1))]),
    {Big, Rest};
%% Atom
term(<<100,Sz:16,Name:Sz/binary,Rest/binary>>) ->
    {list_to_atom(binary_to_list(Name)),Rest};
%% Reference
term(<<114,Len:16,Rest/binary>>) ->
    BLen = (Len*4),
    {Node,<<C,Ref:BLen/binary,NodeRest/binary>>} = term(Rest),
    {{ref,Node,C,Ref},NodeRest};
%% pid
term(<<103,Rest/binary>>) ->
    {Node,<<Id:32,Ser:32,C:8,NodeRest/binary>>} = term(Rest),
    {{pid,Node,Id,Ser,C},NodeRest};
%% NIL
term(<<106,Rest/binary>>) ->
    {[],Rest};
%% num
term(<<97,Num,Rest/binary>>) ->
    {Num,Rest};
%% num
term(<<98,Num:32,Rest/binary>>) ->
    {Num,Rest};
%% String
term(<<107,Len:16,Txt:Len/binary,Rest/binary>>) ->
    {binary_to_list(Txt),Rest};
term(<<>>) ->
    {'$$cut$$',<<>>};
term(R) ->
    {{'$$abc$$',R},<<>>}.