1 files changed, 53 insertions, 0 deletions
diff --git a/src/ss7_helper.erl b/src/ss7_helper.erl
new file mode 100644
index 0000000..194cbad
--- /dev/null
+++ b/src/ss7_helper.erl
@@ -0,0 +1,53 @@
+-module(ss7_helper).
+-author('Daniel Mende <mail@c0decafe.de>').
+
+-export([encode_phonenumber/4, 
+         decode_phonenumber/1,
+         encode_msisdn/4,
+         decode_imsi/1,
+         remove_firstN/2,
+         tup2bin/1]).
+
+decode_imsi(<<>>) ->
+    [];
+decode_imsi(Imsi) ->
+    <<First:4,Second:4,Rest/bits>> = Imsi,
+    Dec = decode_imsi(Rest),
+    if
+      First==15 -> lists:append([Second], Dec);
+      true ->       lists:append([Second,First], Dec)
+    end.
+
+%% ===================================================================
+%% Phone Number helper
+%% ===================================================================
+
+encode_phonenumber(Extension, NatureOfNumber, NumberPlan, Number) ->
+    {EncNumber, Digits} = encode_phonenumber(Number),
+    <<Digits:8, Extension:1, NatureOfNumber:3, NumberPlan:4, EncNumber/binary>>.
+encode_phonenumber([First,Second|Tail]) ->
+    {EncNumber, Digits} = encode_phonenumber(Tail),
+    {<<Second:4, First:4, EncNumber/binary>>, Digits + 2};
+encode_phonenumber([Last]) ->
+    {<<15:4, Last:4>>, 1};
+encode_phonenumber([]) ->
+    {<<>>, 0}.
+
+decode_phonenumber(<<_Extension:1, _NatureOfNumber:1, _NumberPlan:4, Number/binary>>) ->
+    decode_imsi(Number).
+
+encode_msisdn(Extension, NatureOfNumber, NumberPlan, Number) ->
+    {EncNumber, _} = encode_phonenumber(Number),
+    <<Extension:1, NatureOfNumber:3, NumberPlan:4, EncNumber/binary>>.
+
+%% ===================================================================
+%% List helper
+%% ===================================================================
+
+remove_firstN(_, []) -> [];
+remove_firstN(1, [_|T]) -> T;
+remove_firstN(N, [_|T]) -> remove_firstN(N-1, T).
+
+
+tup2bin(Tupel) ->
+    binary:list_to_bin([element(I,Tupel) || I <- lists:seq(1,tuple_size(Tupel))]).