From e96b4bbb802cd00fa14deb12d7200873c7a79e85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 5 Dec 2014 07:48:26 +0100
Subject: asn1ct_parser2: Remove expensive lookahead_assignment/1 function
In the parsing of a value assignment, such as:
value INTEGER ::= 42
there is call to a function called lookahead_assignment/1 that
will ensure that the sequence of tokens that follows the value
is a valid assignment. The problem is that if the next assignment
is a value assignment, that too will look ahead to the next
assignment. That means that the complexity will be quadratic
if there are many value assignments following each other.
The reason for the test in the first place is unclear; my guess
is that it was an attempt to provide better error reporting.
---
lib/asn1/src/asn1ct_parser2.erl | 10 ----------
1 file changed, 10 deletions(-)
(limited to 'lib')
diff --git a/lib/asn1/src/asn1ct_parser2.erl b/lib/asn1/src/asn1ct_parser2.erl
index 7a1c7230b3..488e4af4e0 100644
--- a/lib/asn1/src/asn1ct_parser2.erl
+++ b/lib/asn1/src/asn1ct_parser2.erl
@@ -2133,7 +2133,6 @@ parse_ValueAssignment([#identifier{pos=L1,val=IdName}|Rest]) ->
case Rest2 of
[{'::=',_}|Rest3] ->
{Value,Rest4} = parse_Value(Rest3),
- lookahead_assignment(Rest4),
{#valuedef{pos=L1,name=IdName,type=Type,value=Value,
module=get(asn1_module)},Rest4};
_ ->
@@ -2300,14 +2299,5 @@ identifier2Extvalueref(#identifier{pos=Pos,val=Name}) ->
module=resolve_module(Name),
value=Name}.
-%% lookahead_assignment/1 checks that the next sequence of tokens
-%% in Token contain a valid assignment or the
-%% 'END' token. Otherwise an exception is thrown.
-lookahead_assignment([{'END',_}|_Rest]) ->
- ok;
-lookahead_assignment(Tokens) ->
- {_,_} = parse_Assignment(Tokens),
- ok.
-
parse_error(Tokens) ->
throw({asn1_error,{parse_error,Tokens}}).
--
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