From 6613732f28da2977c308500eacabea5fe332f5fa Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang-solutions.com>
Date: Fri, 8 Jul 2011 10:45:49 +0200
Subject: Optmized decode_length by doing some calculations as compile time
 rather than runtime

---
 lib/asn1/src/asn1ct_constructed_per.erl | 38 ++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

(limited to 'lib/asn1/src/asn1ct_constructed_per.erl')

diff --git a/lib/asn1/src/asn1ct_constructed_per.erl b/lib/asn1/src/asn1ct_constructed_per.erl
index c1b6aa5713..72c8a3fd9a 100644
--- a/lib/asn1/src/asn1ct_constructed_per.erl
+++ b/lib/asn1/src/asn1ct_constructed_per.erl
@@ -469,7 +469,8 @@ gen_decode_sof(Erules,Typename,SeqOrSetOf,D) when is_record(D,type) ->
 	    _ ->
 		""
 	end,
-    emit({nl,"{Num,Bytes1} = ?RT_PER:decode_length(Bytes,",{asis,SizeConstraint},"),",nl}),
+    gen_decode_length(SizeConstraint,
+		      is_optimized(Erules)),
     emit({"'dec_",asn1ct_gen:list2name(Typename),
 	      "_components'(Num, Bytes1, telltype",ObjFun,", []).",nl}),
     NewComponentType =
@@ -480,6 +481,41 @@ gen_decode_sof(Erules,Typename,SeqOrSetOf,D) when is_record(D,type) ->
 	end,
     gen_decode_sof_components(Erules,Typename,SeqOrSetOf,NewComponentType).
 
+%% Logic copied from asn1_per_bin_rt2ct:decode_constrained_number
+gen_decode_length({Lb,Ub},true) when Ub =< 65535, Lb >= 0 ->
+    Range = Ub - Lb + 1,
+    Call = if
+	       Range  == 1 ->
+		   "{0,Bytes}";
+	       Range  == 2 ->
+		   "?RT_PER:getbits(Bytes,1)";
+	       Range  =< 4 ->
+		   "?RT_PER:getbits(Bytes,2)";
+	       Range  =< 8 ->
+		   "?RT_PER:getbits(Bytes,3)";
+	       Range  =< 16 ->
+		   "?RT_PER:getbits(Bytes,4)";
+	       Range  =< 32 ->
+		   "?RT_PER:getbits(Bytes,5)";
+	       Range  =< 64 ->
+		   "?RT_PER:getbits(Bytes,6)";
+	       Range  =< 128 ->
+		   "?RT_PER:getbits(Bytes,7)";
+	       Range  =< 255 ->
+		   "?RT_PER:getbits(Bytes,8)";
+	       Range  =< 256 ->
+		   "?RT_PER:getoctets(Bytes,1)";
+	       Range  =< 65536 ->
+		   "?RT_PER:getoctets(Bytes,2)";
+	       true ->
+		   ["exit({not_supported,{integer_range,",Range,"}}"]
+	   end,
+    emit({nl,"{Val,Remain} = ",Call,",",nl}),
+    emit({nl,"{Num,Bytes1} = {Val+",Lb,",Remain},",nl});
+gen_decode_length(SizeConstraint,_) ->
+    emit({nl,"{Num,Bytes1} = ?RT_PER:decode_length(Bytes,",
+	  {asis,SizeConstraint},"),",nl}).
+
 gen_encode_sof_components(Erule,Typename,SeqOrSetOf,Cont) ->
     {ObjFun,ObjFun_Var} =
 	case Cont#type.tablecinf of
-- 
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