%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2009. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
-module(inets_regexp).
-export([parse/1, match/2, first_match/2, split/2, sub/3, gsub/3]).
%%%=========================================================================
%%% API
%%%=========================================================================
%% parse(RegExp) -> {ok, RE} | {error, E}.
%% Parse the regexp described in the string RegExp.
parse(S) ->
case (catch reg(S)) of
{R, []} ->
{ok, R};
{_R, [C|_]} ->
{error, {illegal, [C]}};
{error, E} ->
{error, E}
end.
%% Find the longest match of RegExp in String.
match(S, RegExp) when is_list(RegExp) ->
case parse(RegExp) of
{ok,RE} -> match(S, RE);
{error,E} -> {error,E}
end;
match(S, RE) ->
case match(RE, S, 1, 0, -1) of
{Start,Len} when Len >= 0 ->
{match, Start, Len};
{_Start,_Len} ->
nomatch
end.
%% Find the first match of RegExp in String.
first_match(S, RegExp) when is_list(RegExp) ->
case parse(RegExp) of
{ok, RE} ->
first_match(S, RE);
{error, E} ->
{error, E}
end;
first_match(S, RE) ->
case first_match(RE, S, 1) of
{Start,Len} when Len >= 0 ->
{match, Start,Len};
nomatch ->
nomatch
end.
first_match(RE, S, St) when S =/= [] ->
case re_apply(S, St, RE) of
{match, P, _Rest} ->
{St, P-St};
nomatch ->
first_match(RE, tl(S), St+1)
end;
first_match(_RE, [], _St) ->
nomatch.
match(RE, S, St, Pos, L) ->
case first_match(RE, S, St) of
{St1, L1} ->
Nst = St1 + 1,
if L1 > L ->
match(RE, lists:nthtail(Nst-St, S), Nst, St1, L1);
true ->
match(RE, lists:nthtail(Nst-St, S), Nst, Pos, L)
end;
nomatch ->
{Pos, L}
end.
%% Split a string into substrings where the RegExp describes the
%% field seperator. The RegExp " " is specially treated.
split(String, " ") -> %This is really special
{ok, RE} = parse("[ \t]+"),
case split_apply(String, RE, true) of
[[]|Ss] ->
{ok,Ss};
Ss ->
{ok,Ss}
end;
split(String, RegExp) when is_list(RegExp) ->
case parse(RegExp) of
{ok, RE} ->
{ok, split_apply(String, RE, false)};
{error, E} ->
{error,E}
end;
split(String, RE) ->
{ok, split_apply(String, RE, false)}.
%% Substitute the first match of the regular expression RegExp
%% with the string Replace in String. Accept pre-parsed regular
%% expressions.
sub(String, RegExp, Rep) when is_list(RegExp) ->
case parse(RegExp) of
{ok, RE} ->
sub(String, RE, Rep);
{error, E} ->
{error, E}
end;
sub(String, RE, Rep) ->
Ss = sub_match(String, RE, 1),
{ok, sub_repl(Ss, Rep, String, 1), length(Ss)}.
%% Substitute every match of the regular expression RegExp with
%% the string New in String. Accept pre-parsed regular expressions.
gsub(String, RegExp, Rep) when is_list(RegExp) ->
case parse(RegExp) of
{ok, RE} ->
gsub(String, RE, Rep);
{error, E} ->
{error, E}
end;
gsub(String, RE, Rep) ->
Ss = matches(String, RE, 1),
{ok, sub_repl(Ss, Rep, String, 1), length(Ss)}.
%%%========================================================================
%%% Internal functions
%%%========================================================================
%% This is the regular expression grammar used. It is equivalent to the
%% one used in AWK, except that we allow ^ $ to be used anywhere and fail
%% in the matching.
%%
%% reg -> reg1 : '$1'.
%% reg1 -> reg1 "|" reg2 : {'or','$1','$2'}.
%% reg1 -> reg2 : '$1'.
%% reg2 -> reg2 reg3 : {concat,'$1','$2'}.
%% reg2 -> reg3 : '$1'.
%% reg3 -> reg3 "*" : {kclosure,'$1'}.
%% reg3 -> reg3 "+" : {pclosure,'$1'}.
%% reg3 -> reg3 "?" : {optional,'$1'}.
%% reg3 -> reg4 : '$1'.
%% reg4 -> "(" reg ")" : '$2'.
%% reg4 -> "\\" char : '$2'.
%% reg4 -> "^" : bos.
%% reg4 -> "$" : eos.
%% reg4 -> "." : char.
%% reg4 -> "[" class "]" : {char_class,char_class('$2')}
%% reg4 -> "[" "^" class "]" : {comp_class,char_class('$3')}
%% reg4 -> "\"" chars "\"" : char_string('$2')
%% reg4 -> char : '$1'.
%% reg4 -> empty : epsilon.
%% The grammar of the current regular expressions. The actual parser
%% is a recursive descent implementation of the grammar.
reg(S) -> reg1(S).
%% reg1 -> reg2 reg1'
%% reg1' -> "|" reg2
%% reg1' -> empty
reg1(S0) ->
{L,S1} = reg2(S0),
reg1p(S1, L).
reg1p([$||S0], L) ->
{R,S1} = reg2(S0),
reg1p(S1, {'or',L,R});
reg1p(S, L) -> {L,S}.
%% reg2 -> reg3 reg2'
%% reg2' -> reg3
%% reg2' -> empty
reg2(S0) ->
{L,S1} = reg3(S0),
reg2p(S1, L).
reg2p([C|S0], L) when (C =/= $|) andalso (C =/= $)) ->
{R,S1} = reg3([C|S0]),
reg2p(S1, {concat,L,R});
reg2p(S, L) -> {L,S}.
%% reg3 -> reg4 reg3'
%% reg3' -> "*" reg3'
%% reg3' -> "+" reg3'
%% reg3' -> "?" reg3'
%% reg3' -> empty
reg3(S0) ->
{L,S1} = reg4(S0),
reg3p(S1, L).
reg3p([$*|S], L) -> reg3p(S, {kclosure,L});
reg3p([$+|S], L) -> reg3p(S, {pclosure,L});
reg3p([$?|S], L) -> reg3p(S, {optional,L});
reg3p(S, L) -> {L,S}.
reg4([$(|S0]) ->
case reg(S0) of
{R,[$)|S1]} -> {R,S1};
{_R,_S} -> throw({error,{unterminated,"("}})
end;
reg4([$\\,O1,O2,O3|S])
when ((O1 >= $0) andalso
(O1 =< $7) andalso
(O2 >= $0) andalso
(O2 =< $7) andalso
(O3 >= $0) andalso
(O3 =< $7)) ->
{(O1*8 + O2)*8 + O3 - 73*$0,S};
reg4([$\\,C|S]) ->
{escape_char(C),S};
reg4([$\\]) ->
throw({error, {unterminated,"\\"}});
reg4([$^|S]) ->
{bos,S};
reg4([$$|S]) ->
{eos,S};
reg4([$.|S]) ->
{{comp_class,"\n"},S};
reg4("[^" ++ S0) ->
case char_class(S0) of
{Cc,[$]|S1]} -> {{comp_class,Cc},S1};
{_Cc,_S} -> throw({error,{unterminated,"["}})
end;
reg4([$[|S0]) ->
case char_class(S0) of
{Cc,[$]|S1]} -> {{char_class,Cc},S1};
{_Cc,_S1} -> throw({error,{unterminated,"["}})
end;
reg4([C|S])
when (C =/= $*) andalso (C =/= $+) andalso (C =/= $?) andalso (C =/= $]) ->
{C, S};
reg4([C|_S]) ->
throw({error,{illegal,[C]}});
reg4([]) ->
{epsilon,[]}.
escape_char($n) -> $\n; %\n = LF
escape_char($r) -> $\r; %\r = CR
escape_char($t) -> $\t; %\t = TAB
escape_char($v) -> $\v; %\v = VT
escape_char($b) -> $\b; %\b = BS
escape_char($f) -> $\f; %\f = FF
escape_char($e) -> $\e; %\e = ESC
escape_char($s) -> $\s; %\s = SPACE
escape_char($d) -> $\d; %\d = DEL
escape_char(C) -> C.
char_class([$]|S]) -> char_class(S, [$]]);
char_class(S) -> char_class(S, []).
char($\\, [O1,O2,O3|S]) when
O1 >= $0, O1 =< $7, O2 >= $0, O2 =< $7, O3 >= $0, O3 =< $7 ->
{(O1*8 + O2)*8 + O3 - 73*$0,S};
char($\\, [C|S]) -> {escape_char(C),S};
char(C, S) -> {C,S}.
char_class([C1|S0], Cc) when C1 =/= $] ->
case char(C1, S0) of
{Cf,[$-,C2|S1]} when C2 =/= $] ->
case char(C2, S1) of
{Cl,S2} when Cf < Cl -> char_class(S2, [{Cf,Cl}|Cc]);
{Cl,_S2} -> throw({error,{char_class,[Cf,$-,Cl]}})
end;
{C,S1} -> char_class(S1, [C|Cc])
end;
char_class(S, Cc) -> {Cc,S}.
%% re_apply(String, StartPos, RegExp) -> re_app_res().
%%
%% Apply the (parse of the) regular expression RegExp to String. If
%% there is a match return the position of the remaining string and
%% the string if else return 'nomatch'. BestMatch specifies if we want
%% the longest match, or just a match.
%%
%% StartPos should be the real start position as it is used to decide
%% if we ae at the beginning of the string.
%%
%% Pass two functions to re_apply_or so it can decide, on the basis
%% of BestMatch, whether to just any take any match or try both to
%% find the longest. This is slower but saves duplicatng code.
re_apply(S, St, RE) -> re_apply(RE, [], S, St).
re_apply(epsilon, More, S, P) -> %This always matches
re_apply_more(More, S, P);
re_apply({'or',RE1,RE2}, More, S, P) ->
re_apply_or(re_apply(RE1, More, S, P),
re_apply(RE2, More, S, P));
re_apply({concat,RE1,RE2}, More, S0, P) ->
re_apply(RE1, [RE2|More], S0, P);
re_apply({kclosure,CE}, More, S, P) ->
%% Be careful with the recursion, explicitly do one call before
%% looping.
re_apply_or(re_apply_more(More, S, P),
re_apply(CE, [{kclosure,CE}|More], S, P));
re_apply({pclosure,CE}, More, S, P) ->
re_apply(CE, [{kclosure,CE}|More], S, P);
re_apply({optional,CE}, More, S, P) ->
re_apply_or(re_apply_more(More, S, P),
re_apply(CE, More, S, P));
re_apply(bos, More, S, 1) -> re_apply_more(More, S, 1);
re_apply(eos, More, [$\n|S], P) -> re_apply_more(More, S, P);
re_apply(eos, More, [], P) -> re_apply_more(More, [], P);
re_apply({char_class,Cc}, More, [C|S], P) ->
case in_char_class(C, Cc) of
true -> re_apply_more(More, S, P+1);
false -> nomatch
end;
re_apply({comp_class,Cc}, More, [C|S], P) ->
case in_char_class(C, Cc) of
true -> nomatch;
false -> re_apply_more(More, S, P+1)
end;
re_apply(C, More, [C|S], P) when is_integer(C) ->
re_apply_more(More, S, P+1);
re_apply(_RE, _More, _S, _P) -> nomatch.
%% re_apply_more([RegExp], String, Length) -> re_app_res().
re_apply_more([RE|More], S, P) -> re_apply(RE, More, S, P);
re_apply_more([], S, P) -> {match,P,S}.
%% in_char_class(Char, Class) -> bool().
in_char_class(C, [{C1,C2}|_Cc]) when C >= C1, C =< C2 -> true;
in_char_class(C, [C|_Cc]) -> true;
in_char_class(C, [_|Cc]) -> in_char_class(C, Cc);
in_char_class(_C, []) -> false.
%% re_apply_or(Match1, Match2) -> re_app_res().
%% If we want the best match then choose the longest match, else just
%% choose one by trying sequentially.
re_apply_or({match,P1,S1}, {match,P2,_S2}) when P1 >= P2 -> {match,P1,S1};
re_apply_or({match,_P1,_S1}, {match,P2,S2}) -> {match,P2,S2};
re_apply_or(nomatch, R2) -> R2;
re_apply_or(R1, nomatch) -> R1.
matches(S, RE, St) ->
case first_match(RE, S, St) of
{St1,0} ->
[{St1,0}|matches(string:substr(S, St1+2-St), RE, St1+1)];
{St1,L1} ->
[{St1,L1}|matches(string:substr(S, St1+L1+1-St), RE, St1+L1)];
nomatch ->
[]
end.
sub_match(S, RE, St) ->
case first_match(RE, S, St) of
{St1,L1} -> [{St1,L1}];
nomatch -> []
end.
sub_repl([{St,L}|Ss], Rep, S, Pos) ->
Rs = sub_repl(Ss, Rep, S, St+L),
string:substr(S, Pos, St-Pos) ++
sub_repl(Rep, string:substr(S, St, L), Rs);
sub_repl([], _Rep, S, Pos) ->
string:substr(S, Pos).
sub_repl([$&|Rep], M, Rest) -> M ++ sub_repl(Rep, M, Rest);
sub_repl("\\&" ++ Rep, M, Rest) -> [$&|sub_repl(Rep, M, Rest)];
sub_repl([C|Rep], M, Rest) -> [C|sub_repl(Rep, M, Rest)];
sub_repl([], _M, Rest) -> Rest.
split_apply(S, RE, Trim) -> split_apply(S, 1, RE, Trim, []).
split_apply([], _P, _RE, true, []) ->
[];
split_apply([], _P, _RE, _T, Sub) ->
[lists:reverse(Sub)];
split_apply(S, P, RE, T, Sub) ->
case re_apply(S, P, RE) of
{match,P,_Rest} ->
split_apply(tl(S), P+1, RE, T, [hd(S)|Sub]);
{match,P1,Rest} ->
[lists:reverse(Sub)|split_apply(Rest, P1, RE, T, [])];
nomatch ->
split_apply(tl(S), P+1, RE, T, [hd(S)|Sub])
end.
