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|
-module(cord_regexp).
-compile(export_all).
%%-export([Function/Arity, ...]).
first_match(RE, Cord) ->
first_match(RE, Cord, 1).
first_match(RE, Cord, Pos) ->
first_match(RE, Cord, Pos, forward).
%% Find the first match of RE in Cord starting from Pos.
first_match(RE, Cord, Pos, Dir) ->
case first_match_c(RE, Cord, Pos, Dir) of
{{match, Start, Len}, WalkerOut} ->
{match, Start, Len};
X ->
X
end.
first_match_c(RE, Cord) ->
first_match_c(RE, Cord, 1).
first_match_c(RE, Cord, Pos) ->
first_match_c(RE, Cord, Pos, forward).
first_match_c(RE, Cord, Pos, forward) ->
{_, Region} = cord:split(Cord, Pos-1),
first_match1(RE, cord:walker(Region, forward), Pos);
first_match_c(RE, Cord, Pos, backward) ->
case regexp:parse(RE) of
{ok, REP} ->
{Region,_} = cord:split(Cord, Pos),
RREP = reverse(REP),
case first_match1(RREP, cord:walker(Region, backward), Pos) of
{{match, S, L}, C} ->
{{match, S, L}, C};
X ->
X
end;
{error, Rsn} ->
{error, Rsn}
end.
continue_match(RE, {W, N}) ->
case first_match1(RE, W, N) of
{{match, S, L}, C} ->
{{match, S, L}, {C, S+L}};
X ->
X
end.
first_match1(RE, W, Pos) when is_list(RE) ->
case regexp:parse(RE) of
{ok, REP} ->
first_match1(optimise(REP), W, Pos);
X = {error, Rsn} ->
X
end;
first_match1(RE, Walker, Pos) ->
case cord:walker_at_end(Walker) of
true ->
nomatch;
false ->
Start = case cord:walker_direction(Walker) of
forward -> 1;
backward -> Pos
end,
case apply_regexp(RE, Start, Walker) of
nomatch ->
%% it would be more efficient to use Walker to get
%% a new continuation to recurse with
{_, W1} = cord:walker_next(Walker),
first_match1(RE, W1, advance(Pos, W1));
{match, EndPos, WalkerOut} ->
Len = case cord:walker_direction(Walker) of
forward -> EndPos;
backward -> Pos - EndPos - 1
end,
{{match, Pos, Len}, WalkerOut}
end
end.
apply_regexp(RE, Pos, W) ->
{Ch, W1} = cord:walker_next(W),
re_apply(RE, [], Ch, Pos, W1).
%% re_apply(RE, More, ThisChar, Pos, InputCont) => {match, Len} | nomatch
%% FIXME: Handling of bos (^) and eos ($) need thinking about when it
%% comes to backwards-searching. Right now, ^ will match the end when
%% going backwards.
re_apply(epsilon, More, Ch, P, C) ->
re_apply_more(More, P, push(Ch, C));
re_apply(eos, More, done, P, C) ->
case cord:walker_direction(C) of
forward ->
re_apply_more(More, P, C);
backward ->
nomatch
end;
re_apply(eos, More, $\n, P, C) ->
re_apply_more(More, P, push($\n, C)); % \n isn't consumed
re_apply(bos, More, done, P, C) ->
case cord:walker_direction(C) of
forward -> nomatch;
backward -> re_apply_more(More, P, C)
end;
re_apply({'or', RE1, RE2}, More, Ch, P, C) ->
re_apply_or({apply, RE1, More, Ch, P, C},
{apply, RE2, More, Ch, P, C});
re_apply({concat, RE1, RE2}, More, Ch, P, C) ->
re_apply(RE1, [RE2|More], Ch, P, C);
re_apply({kclosure, CE}, More, Ch, P, C) ->
re_apply_or({apply_more, More, P, push(Ch, C)},
{apply, CE, [{kclosure, CE}|More], Ch, P, C});
re_apply({pclosure, CE}, More, Ch, P, C) ->
re_apply(CE, [{kclosure, CE}|More], Ch, P, C);
re_apply({optional, CE}, More, Ch, P, C) ->
re_apply_or({apply_more, More, P, push(Ch, C)},
{apply, CE, More, Ch, P, C});
re_apply(bos, More, Ch, 1, C) ->
case cord:walker_direction(C) of
forward -> re_apply_more(More, 1, push(Ch, C));
backward -> nomatch
end;
re_apply(bos, More, $\n, P, C) ->
re_apply_more(More, 1, push($\n, C)); % \n isn't consumed
re_apply({char_class, Cc}, More, Ch, P, C) ->
case in_char_class(Ch, Cc) of
true -> re_apply_more(More, advance(P, C), C);
false -> nomatch
end;
re_apply({comp_class, Cc}, More, Ch, P, C) ->
case in_char_class(Ch, Cc) of
true -> nomatch;
false -> re_apply_more(More, advance(P, C), C)
end;
re_apply(Ch, More, Ch, P, C) when is_integer(Ch) ->
re_apply_more(More, advance(P, C), C);
re_apply(_, _, _, _, _) ->
nomatch.
advance(Pos, Walker) ->
case cord:walker_direction(Walker) of
forward -> Pos + 1;
backward -> Pos - 1
end.
re_apply_more([H|T], P, C) ->
{Next, C1} = cord:walker_next(C),
re_apply(H, T, Next, P, C1);
re_apply_more([], P, C) ->
%% -1 isn't used in 'regexp' module, not sure what's different..
{match, P-1, C}.
re_apply_or(A, B) ->
case re_apply_or_operand(A) of
nomatch ->
re_apply_or_operand(B);
X ->
X
end.
re_apply_or_operand({apply_more, More, P, C}) ->
re_apply_more(More, P, C);
re_apply_or_operand({apply, RE, More, Ch, P, C}) ->
re_apply(RE, More, Ch, P, C).
% re_apply_or({match,P1}, {match,P2}) when P1 >= P2 -> {match,P1};
% re_apply_or({match,P1}, {match,P2}) -> {match,P2};
% re_apply_or(nomatch, R2) -> R2;
% re_apply_or(R1, nomatch) -> R1.
in_char_class(C, [{C1,C2}|Cc]) when C >= C1, C =< C2 -> true;
in_char_class(C, [C|Cc]) -> true;
in_char_class(C, [_|Cc]) -> in_char_class(C, Cc);
in_char_class(C, []) -> false.
push(Ch, Cont) ->
cord:walker_push(Ch, Cont).
%% reverse(RE)
%% Returns an equivalent regexp which takes its input in reverse order.
%% RE should come from regexp:parse/1
reverse({'or', A, B}) ->
{'or', reverse(B), reverse(A)};
reverse({concat, A, B}) ->
{concat, reverse(B), reverse(A)};
reverse({optional, RE}) ->
{optional, reverse(RE)};
reverse({kclosure, RE}) ->
{kclosure, reverse(RE)};
reverse({pclosure, RE}) ->
{pclosure, reverse(RE)};
reverse(Other) ->
Other.
%% Just trivial stuff for starters.
%%
%% Rearrange concat
optimise({concat, {concat, A, B}, C}) ->
optimise({concat, A, {concat, B, C}});
%% recurse
optimise({'or', A, B}) ->
{'or', optimise(A), optimise(B)};
optimise({kclosure, A}) ->
{kclosure, optimise(A)};
optimise({pclosure, A}) ->
{pclosure, optimise(A)};
optimise({optional, A}) ->
{optional, optimise(A)};
optimise(X) ->
X.
test_exprs() ->
["foo",
"a|b",
"(foo)|(bar)",
"a+"].
test_inputs() ->
["foo", "a", "b", "c", "foo", "bar", "baz", "aaaaa"].
test() ->
case [{Inp, RE} || RE <- test_exprs(), Inp <- test_inputs(),
not same(Inp, RE)] of
[] ->
ok;
%% BadOnes is where the match result was different. BUT!
%% sometimes that is OK. At time of writing, the code seems
%% correct but has some BadOnes.
BadOnes ->
lists:foreach(fun complain/1, BadOnes)
end.
same(Inp, REStr) ->
forwards(Inp, REStr) == backwards(Inp, REStr).
forwards(Inp, RE) ->
regexp:match(Inp, RE).
backwards(Inp, REStr) ->
{ok, RE} = regexp:parse(REStr),
BackwardsResult = regexp:match(lists:reverse(Inp), reverse(RE)).
complain({Inp, REStr}) ->
{ok, RE} = regexp:parse(REStr),
ForwardsResult = regexp:match(Inp, RE),
BackwardsResult = regexp:match(lists:reverse(Inp), reverse(RE)),
io:format("match(~p, ~p):~n Fwds = ~p~n Bwds = ~p~n",
[Inp, REStr, ForwardsResult, BackwardsResult]).
%% Compare speed of this module on a cord to the speed of the 'regexp'
%% module on a string.
bench(Regexp, Cord) ->
List = cord:to_list(Cord),
{CordSpeed,_} = timer:tc(?MODULE, first_match, [Regexp, Cord]),
{ListSpeed, _} = timer:tc(regexp, first_match, [List, Regexp]),
io:format("Cord takes ~p% time of List (~pms vs ~pms).~n",
[round(CordSpeed * 100 / ListSpeed),
round(CordSpeed/1000),
round(ListSpeed/1000)]).
escape([H|T]) ->
case lists:member(H, specials()) of
true ->
[$\\,H|escape(T)];
false ->
[H|escape(T)]
end;
escape([]) ->
[].
specials() -> "()^$[]*+?.\\|".
|
