PER: Optimize encoding of character strings with simple ranges

The encoder for the following type would generate a dialyzer warning:

  Ns ::= NumericString (FROM ("0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9"))

Optimize this case to make it slightly faster as well as eliminate
the dialyzer warning.

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/asn1/src/asn1rtt_per_common.erl b/lib/asn1/src/asn1rtt_per_common.erl
index 71fec411a0..0290c75a28 100644
--- a/lib/asn1/src/asn1rtt_per_common.erl
+++ b/lib/asn1/src/asn1rtt_per_common.erl
@@ -30,6 +30,7 @@
 	 decode_big_chars/2,
 	 decode_oid/1,decode_relative_oid/1,
 	 encode_chars/2,encode_chars/3,
+	 encode_chars_compact_map/3,
 	 encode_chars_16bit/1,encode_big_chars/1,
 	 encode_fragmented/2,
 	 encode_oid/1,encode_relative_oid/1,
@@ -108,6 +109,9 @@ encode_chars(Val, NumBits) ->
 encode_chars(Val, NumBits, {Lb,Tab}) ->
     << <<(enc_char(C, Lb, Tab)):NumBits>> || C <- Val >>.
 
+encode_chars_compact_map(Val, NumBits, {Lb,Limit}) ->
+    << <<(enc_char_cm(C, Lb, Limit)):NumBits>> || C <- Val >>.
+
 encode_chars_16bit(Val) ->
     L = [case C of
 	     {0,0,A,B} -> [A,B];
@@ -383,6 +387,15 @@ enc_char(C0, Lb, Tab) ->
 	    illegal_char_error()
     end.
 
+enc_char_cm(C0, Lb, Limit) ->
+    C = C0 - Lb,
+    if
+	0 =< C, C < Limit ->
+	    C;
+	true ->
+	    illegal_char_error()
+    end.
+
 illegal_char_error() ->
     error({error,{asn1,"value forbidden by FROM constraint"}}).