Use GSUP APN as Service-Selection field
Previous the osmo-hlr always sent a wildcard APN as the only APN
which violates the spec. Further wildcard APNs aren't support
by the current Open5gs.
Since I540132ee5dcfd09f4816e02e702927e1074ca50f the osmo-hlr
supports multiple APN in the subscriber data.
Related: SYS#6391
Change-Id: I2a0af5d785ce62968f6e3952602d92cb4f37e4ab
diff --git a/src/decode_apn.erl b/src/decode_apn.erl
new file mode 100644
index 0000000..ea12bc6
--- /dev/null
+++ b/src/decode_apn.erl
@@ -0,0 +1,51 @@
+
+-module(decode_apn).
+
+% decode APN Name Encoded Format
+% TS 23.003 APN
+-export([decode_apn/1, encode_apn/1]).
+
+decode_apn(ApnEnc) ->
+ decode_apn("", ApnEnc, 0).
+
+decode_apn(Result, [], 0) ->
+ Result;
+
+decode_apn(Result, << >>, 0) ->
+ Result;
+
+decode_apn("", ApnEnc, 0) ->
+ << NewElemLen:8, RemainEnc/bytes >> = ApnEnc,
+ case NewElemLen of
+ 0 -> "";
+ _ -> decode_apn("", RemainEnc, NewElemLen)
+ end;
+
+decode_apn(Result, ApnEnc, 0) ->
+ << NewElemLen:8, RemainEnc/bytes >> = ApnEnc,
+ case NewElemLen of
+ 0 -> Result;
+ _ -> decode_apn(Result ++ ".", RemainEnc, NewElemLen)
+ end;
+
+decode_apn(Result, ApnEnc, RemainLen) when RemainLen > 0 ->
+ << Char:8, RemainEnc/bytes >> = ApnEnc,
+ decode_apn(Result ++ [Char], RemainEnc, RemainLen - 1).
+
+encode_apn(ApnStr) ->
+ encode_apn(<<>>, ApnStr, "", 0).
+
+encode_apn(ApnEnc, "", "", 0) ->
+ ApnEnc;
+
+encode_apn(ApnEnc, "", CurStr, Len) ->
+ CurBin = binary:list_to_bin(CurStr),
+ Result = << ApnEnc/binary, Len, CurBin/binary >>,
+ Result;
+
+encode_apn(ApnEnc, [ Char | RemainStr ], CurStr, Len) ->
+ case Char of
+ 46 -> CurBin = binary:list_to_bin(CurStr),
+ encode_apn(<<ApnEnc/binary, Len, CurBin/binary >>, RemainStr, "", 0);
+ _ -> encode_apn(ApnEnc, RemainStr, CurStr ++ [Char], Len + 1)
+ end.