%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2008-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
-module(re).
-export([grun/3,urun/3,ucompile/2,replace/3,replace/4,split/2,split/3]).

%-opaque mp() :: {re_pattern, _, _, _}.
-type mp() :: {re_pattern, _, _, _}.

-type nl_spec() :: cr | crlf | lf | anycrlf | any.

-type compile_option() :: unicode | anchored | caseless | dollar_endonly
                        | dotall | extended | firstline | multiline
                        | no_auto_capture | dupnames | ungreedy
                        | {newline, nl_spec()}| bsr_anycrlf
                        | bsr_unicode.

%% Emulator builtins in this module:
%% re:compile/1
%% re:compile/2
%% re:run/2
%% re:run/3

-spec split(Subject, RE) -> SplitList when
      Subject :: iodata() | unicode:charlist(),
      RE :: mp() | iodata(),
      SplitList :: [iodata() | unicode:charlist()].

split(Subject,RE) ->
    split(Subject,RE,[]).

-spec split(Subject, RE, Options) -> SplitList when
      Subject :: iodata() | unicode:charlist(),
      RE :: mp() | iodata() | unicode:charlist(),
      Options :: [ Option ],
      Option :: anchored | notbol | noteol | notempty
              | {offset, non_neg_integer()} | {newline, nl_spec()}
              | bsr_anycrlf | bsr_unicode | {return, ReturnType}
              | {parts, NumParts} | group | trim | CompileOpt,
      NumParts :: non_neg_integer() | infinity,
      ReturnType :: iodata | list | binary,
      CompileOpt :: compile_option(),
      SplitList :: [RetData] | [GroupedRetData],
      GroupedRetData :: [RetData],
      RetData :: iodata() | unicode:charlist() | binary() | list().

split(Subject,RE,Options) ->
    try
    {NewOpt,Convert,Unicode,Limit,Strip,Group} =
	process_split_params(Options,iodata,false,-1,false,false),
    FlatSubject = to_binary(Subject, Unicode),
    case compile_split(RE,NewOpt) of
	{error,_Err} ->
	    throw(badre);
	{PreCompiled, NumSub, RunOpt} ->
	    %% OK, lets run
	    case re:run(FlatSubject,PreCompiled,RunOpt ++ [global]) of
		nomatch ->
		    case Group of
			true ->
			    convert_any_split_result([[FlatSubject]], 
						     Convert, Unicode, true);
			false ->
			    convert_any_split_result([FlatSubject], 
						     Convert, Unicode, false)
		    end;
		{match, Matches} ->
		    Res = do_split(FlatSubject, 0, Matches, NumSub, 
				   Limit, Group),
		    Stripped = case Strip of
				   true ->
				       backstrip_empty(Res,Group);
				   false ->
				       Res
			       end,
		    convert_any_split_result(Stripped, Convert, Unicode, Group)
	    end
    end
    catch
	throw:badopt ->
	    erlang:error(badarg,[Subject,RE,Options]);
	throw:badre ->
	    erlang:error(badarg,[Subject,RE,Options]);
	error:badarg ->
	    erlang:error(badarg,[Subject,RE,Options])
    end.

backstrip_empty(List, false) ->
    do_backstrip_empty(List);
backstrip_empty(List, true) ->
    do_backstrip_empty_g(List).

do_backstrip_empty_g([]) ->
    [];
do_backstrip_empty_g([H]) ->
    case do_backstrip_empty(H) of
	[] ->
	    [];
	_ ->
	    [H]
    end;
do_backstrip_empty_g([H|T]) ->
    case do_backstrip_empty_g(T) of
	[] ->
	    case do_backstrip_empty(H) of
		[] ->
		    [];
		_ ->
		    [H]
	    end;
	Other ->
	    [H|Other]
    end.

do_backstrip_empty([]) ->
    [];
do_backstrip_empty([<<>>]) ->
    [];
do_backstrip_empty([<<>>|T]) ->
    case do_backstrip_empty(T) of
	[] ->
	    [];
	Other ->
	    [<<>>|Other]
    end;
do_backstrip_empty([H|T]) ->
    [H|do_backstrip_empty(T)].

convert_any_split_result(List,Type,Uni,true) ->
    [ convert_split_result(Part,Type,Uni) || Part <- List ];
convert_any_split_result(List,Type,Uni, false) ->
    convert_split_result(List,Type,Uni).

convert_split_result(List, iodata, _Unicode) ->
    List;
convert_split_result(List, binary, _Unicode) ->
    %% As it happens, the iodata is actually binaries
    List;
convert_split_result(List, list, true) ->
    [unicode:characters_to_list(Element,unicode) || Element <- List];
convert_split_result(List, list, false) ->
    [binary_to_list(Element) || Element <- List].

do_split(Subj, Off,  _, _, 0, false) ->
    <<_:Off/binary,Rest/binary>> = Subj,
    [Rest];
do_split(Subj, Off, [], _, _, false) ->
    <<_:Off/binary,Rest/binary>> = Subj,
    [Rest];
do_split(Subj, Off, _, _, _,false) when byte_size(Subj) =< Off ->
    [<<>>];
do_split(Subj, Off,  _, _, 0, true) ->
    <<_:Off/binary,Rest/binary>> = Subj,
    [[Rest]];
do_split(Subj, Off, [], _, _, true) ->
    <<_:Off/binary,Rest/binary>> = Subj,
    [[Rest]];
do_split(Subj, Off, _, _, _,true) when byte_size(Subj) =< Off ->
    [[<<>>]];
do_split(Subj, Offset, [[{MainI,MainL}|Sub]|T], NumSub, Limit, Group) ->
    NewOffset = MainI+MainL,
    KeptLen =  MainI - Offset,
    case {KeptLen,empty_sub(Sub),MainL} of
	{0,true,0} ->
	    do_split(Subj,NewOffset,T,NumSub,Limit,Group);
	_ ->
	    <<_:Offset/binary,Keep:KeptLen/binary,_/binary>> = Subj,
	    ESub = extend_subpatterns(Sub,NumSub),
	    Tail = do_split(Subj, NewOffset, T, NumSub, Limit - 1,Group),
	    case Group of
		false ->
		    [Keep | dig_subpatterns(Subj,lists:reverse(ESub),Tail)];
		true ->
		    [[Keep | dig_subpatterns(Subj,lists:reverse(ESub),[])]|
		     Tail]
	    end
    end.
empty_sub([]) ->
    true;
empty_sub([{_,0}|T]) ->
    empty_sub(T);
empty_sub(_) ->
    false.

dig_subpatterns(_,[],Acc) ->
    Acc;
dig_subpatterns(Subj,[{-1,0}|T],Acc) ->
    dig_subpatterns(Subj,T,[<<>>|Acc]);
dig_subpatterns(Subj,[{I,L}|T],Acc) ->
    <<_:I/binary,Part:L/binary,_/binary>> = Subj,
    dig_subpatterns(Subj,T,[Part|Acc]).

extend_subpatterns(_,0) ->
    [];
extend_subpatterns([],N) ->
    [{0,0} | extend_subpatterns([],N-1)];
extend_subpatterns([H|T],N) ->
    [H | extend_subpatterns(T,N-1)].

compile_split({re_pattern,N,_,_} = Comp, Options) ->
    {Comp,N,Options};
compile_split(Pat,Options0) when not is_tuple(Pat) ->
    Options = lists:filter(fun(O) ->
				   (not runopt(O))
			   end, Options0),
    case re:compile(Pat,Options) of
	{error,Err} ->
	    {error,Err};
	{ok, {re_pattern,N,_,_} = Comp} ->
	    NewOpt = lists:filter(fun(OO) -> (not copt(OO)) end, Options0),
	    {Comp,N,NewOpt}
    end;
compile_split(_,_) ->
    throw(badre).
    
-spec replace(Subject, RE, Replacement) -> iodata() | unicode:charlist() when
      Subject :: iodata() | unicode:charlist(),
      RE :: mp() | iodata(),
      Replacement :: iodata() | unicode:charlist().

replace(Subject,RE,Replacement) ->
    replace(Subject,RE,Replacement,[]).

-spec replace(Subject, RE, Replacement, Options) -> iodata() | unicode:charlist() when
      Subject :: iodata() | unicode:charlist(),
      RE :: mp() | iodata() | unicode:charlist(),
      Replacement :: iodata() | unicode:charlist(),
      Options :: [Option],
      Option :: anchored | global | notbol | noteol | notempty
              | {offset, non_neg_integer()} | {newline, NLSpec} | bsr_anycrlf
              | bsr_unicode | {return, ReturnType} | CompileOpt,
      ReturnType :: iodata | list | binary,
      CompileOpt :: compile_option(),
      NLSpec :: cr | crlf | lf | anycrlf | any.

replace(Subject,RE,Replacement,Options) ->
    try
    {NewOpt,Convert,Unicode} =
	process_repl_params(Options,iodata,false),
    FlatSubject = to_binary(Subject, Unicode),
    FlatReplacement = to_binary(Replacement, Unicode),
    IoList = do_replace(FlatSubject,Subject,RE,FlatReplacement,NewOpt),
	case Convert of
	    iodata ->
		IoList;
	    binary ->
		case Unicode of
		    false ->
			iolist_to_binary(IoList);
		    true ->
			unicode:characters_to_binary(IoList,unicode)
		end;
	    list ->
		case Unicode of
		    false ->
			binary_to_list(iolist_to_binary(IoList));
		    true ->
			unicode:characters_to_list(IoList,unicode)
		end
	end
    catch
	throw:badopt ->
	    erlang:error(badarg,[Subject,RE,Replacement,Options]);
	throw:badre ->
	    erlang:error(badarg,[Subject,RE,Replacement,Options]);
	error:badarg ->
	    erlang:error(badarg,[Subject,RE,Replacement,Options])
    end.


do_replace(FlatSubject,Subject,RE,Replacement,Options) ->
    case re:run(FlatSubject,RE,Options) of
	nomatch ->
	    Subject;
	{match,[Mlist|T]} when is_list(Mlist) ->
	    apply_mlist(FlatSubject,Replacement,[Mlist|T]);
	{match,Slist} ->
	    apply_mlist(FlatSubject,Replacement,[Slist])
    end.

process_repl_params([],Convert,Unicode) ->
    {[],Convert,Unicode};
process_repl_params([unicode|T],C,_U) ->
    {NT,NC,NU} = process_repl_params(T,C,true), 
    {[unicode|NT],NC,NU};
process_repl_params([{capture,_,_}|_],_,_) ->
    throw(badopt);
process_repl_params([{capture,_}|_],_,_) ->
    throw(badopt);
process_repl_params([{return,iodata}|T],_C,U) ->
    process_repl_params(T,iodata,U);
process_repl_params([{return,list}|T],_C,U) ->
    process_repl_params(T,list,U);
process_repl_params([{return,binary}|T],_C,U) ->
    process_repl_params(T,binary,U);
process_repl_params([{return,_}|_],_,_) ->
    throw(badopt);
process_repl_params([H|T],C,U) ->
    {NT,NC,NU} = process_repl_params(T,C,U),
    {[H|NT],NC,NU}.

process_split_params([],Convert,Unicode,Limit,Strip,Group) ->
    {[],Convert,Unicode,Limit,Strip,Group};
process_split_params([unicode|T],C,_U,L,S,G) ->
    {NT,NC,NU,NL,NS,NG} = process_split_params(T,C,true,L,S,G), 
    {[unicode|NT],NC,NU,NL,NS,NG};
process_split_params([trim|T],C,U,_L,_S,G) ->
    process_split_params(T,C,U,-1,true,G); 
process_split_params([{parts,0}|T],C,U,_L,_S,G) ->
    process_split_params(T,C,U,-1,true,G); 
process_split_params([{parts,N}|T],C,U,_L,_S,G) when is_integer(N), N >= 1 ->
    process_split_params(T,C,U,N-1,false,G); 
process_split_params([{parts,infinity}|T],C,U,_L,_S,G) ->
    process_split_params(T,C,U,-1,false,G); 
process_split_params([{parts,_}|_],_,_,_,_,_) ->
    throw(badopt); 
process_split_params([group|T],C,U,L,S,_G) ->
    process_split_params(T,C,U,L,S,true); 
process_split_params([global|_],_,_,_,_,_) ->
    throw(badopt);
process_split_params([{capture,_,_}|_],_,_,_,_,_) ->
    throw(badopt);
process_split_params([{capture,_}|_],_,_,_,_,_) ->
    throw(badopt);
process_split_params([{return,iodata}|T],_C,U,L,S,G) ->
    process_split_params(T,iodata,U,L,S,G);
process_split_params([{return,list}|T],_C,U,L,S,G) ->
    process_split_params(T,list,U,L,S,G);
process_split_params([{return,binary}|T],_C,U,L,S,G) ->
    process_split_params(T,binary,U,L,S,G);
process_split_params([{return,_}|_],_,_,_,_,_) ->
    throw(badopt);
process_split_params([H|T],C,U,L,S,G) ->
    {NT,NC,NU,NL,NS,NG} = process_split_params(T,C,U,L,S,G),
    {[H|NT],NC,NU,NL,NS,NG}.

apply_mlist(Subject,Replacement,Mlist) ->
    do_mlist(Subject,Subject,0,precomp_repl(Replacement), Mlist).


precomp_repl(<<>>) ->
    [];
precomp_repl(<<$\\,X,Rest/binary>>) when X < $1 ; X > $9 ->
    %% Escaped character
    case precomp_repl(Rest) of
	[BHead | T0] when is_binary(BHead) ->
	    [<<X,BHead/binary>> | T0];
	Other ->
	    [<<X>> | Other]
    end;
precomp_repl(<<$\\,Rest/binary>>) when byte_size(Rest) > 0->
    {NS,NRest} = pick_int(Rest),
    [list_to_integer(NS) | precomp_repl(NRest)];
precomp_repl(<<$&,Rest/binary>>) ->
    [0 | precomp_repl(Rest)];
precomp_repl(<<X,Rest/binary>>) ->
    case precomp_repl(Rest) of
	[BHead | T0] when is_binary(BHead) ->
	    [<<X,BHead/binary>> | T0];
	Other ->
	    [<<X>> | Other]
    end.
    


pick_int(<<X,R/binary>>) when X >= $0, X =< $9 ->
    {Found,Rest} = pick_int(R),
    {[X|Found],Rest};
pick_int(Bin) ->
    {[],Bin}.

do_mlist(_,<<>>,_,_,[]) ->
    []; %Avoid empty binary tail
do_mlist(_,Subject,_,_,[]) ->
    Subject;
do_mlist(Whole,Subject,Pos,Repl,[[{MPos,Count} | Sub] | Tail]) 
  when MPos > Pos ->
    EatLength = MPos - Pos,
    <<Untouched:EatLength/binary, Rest/binary>> = Subject,
    [Untouched | do_mlist(Whole,Rest, MPos, Repl, 
			  [[{MPos,Count} | Sub] | Tail])];
do_mlist(Whole,Subject,Pos,Repl,[[{MPos,Count} | Sub] | Tail]) 
  when MPos =:= Pos ->
    EatLength = Count,
    <<_:EatLength/binary,Rest/binary>> = Subject,
    NewData = do_replace(Whole,Repl,[{MPos,Count} | Sub]),
    [NewData | do_mlist(Whole,Rest,Pos+EatLength,Repl,Tail)].


do_replace(_,[Bin],_) when is_binary(Bin) ->
    Bin;
do_replace(Subject,Repl,SubExprs0) ->
    SubExprs = list_to_tuple(SubExprs0),
    [ case Part of
	  N when is_integer(N) ->
	      if
		  tuple_size(SubExprs) =< N ->
		      <<>>;
		  true ->
		      {SPos,SLen} = element(N+1,SubExprs),
		      if 
			  SPos < 0 ->
			      <<>>;
			  true ->
			      <<_:SPos/binary,Res:SLen/binary,_/binary>> = 
				  Subject,
			      Res
		      end
	      end;
	  Other ->
	      Other
      end || Part <- Repl ].


check_for_unicode({re_pattern,_,1,_},_) ->
    true;
check_for_unicode({re_pattern,_,0,_},_) ->
    false;
check_for_unicode(_,L) ->
    lists:member(unicode,L).
    
% SelectReturn = false | all | stirpfirst | none 
% ConvertReturn = index | list | binary
% {capture, all} -> all (untouchded)
% {capture, first} -> kept in argumentt list and Select all
% {capture, all_but_first} -> removed from argument list and selects stripfirst
% {capture, none} ->  removed from argument list and selects none
% {capture, []} -> removed from argument list and selects none
% {capture,[...]} -> 0 added to selection list and selects stripfirst
% SelectReturn false is same as all in the end.

% Call as process_parameters([],0,false,index,NeedClean)

process_parameters([],InitialOffset, SelectReturn, ConvertReturn,_) ->
    {[], InitialOffset, SelectReturn, ConvertReturn};
process_parameters([{offset, N} | T],_Init0,Select0,Return0,CC) ->
    process_parameters(T,N,Select0,Return0,CC);
process_parameters([global | T],Init0,Select0,Return0,CC) ->
    process_parameters(T,Init0,Select0,Return0,CC);
process_parameters([{capture,Values,Type}|T],Init0,Select0,_Return0,CC) ->
    process_parameters([{capture,Values}|T],Init0,Select0,Type,CC);
process_parameters([{capture,Values}|T],Init0,Select0,Return0,CC) ->
    % First process the rest to see if capture was already present
    {NewTail, Init1, Select1, Return1} = 
	process_parameters(T,Init0,Select0,Return0,CC),
    case Select1 of
	false ->
	    case Values of
		all ->
		    {[{capture,all} | NewTail], Init1, all, Return0}; 
		first ->
		    {[{capture,first} | NewTail], Init1, all, Return0};
		all_but_first ->
		    {[{capture,all} | NewTail], Init1, stripfirst, Return0};
		none ->
		    {[{capture,first} | NewTail], Init1, none, Return0};
		[] ->
		    {[{capture,first} | NewTail], Init1, none, Return0};
		List when is_list(List) ->
		    {[{capture,[0|List]} | NewTail], 
		     Init1, stripfirst, Return0};
		_ ->
		    throw(badlist)
	    end;
	_ ->
	    % Found overriding further down list, ignore this one
	    {NewTail, Init1, Select1, Return1}
    end;
process_parameters([H|T],Init0,Select0,Return0,true) ->
    case copt(H) of
	true ->
	    process_parameters(T,Init0,Select0,Return0,true);
	false ->
	    {NewT,Init,Select,Return} =
		process_parameters(T,Init0,Select0,Return0,true),	
	    {[H|NewT],Init,Select,Return}
    end;
process_parameters([H|T],Init0,Select0,Return0,false) ->
    {NewT,Init,Select,Return} =
		process_parameters(T,Init0,Select0,Return0,false),
    {[H|NewT],Init,Select,Return};
process_parameters(_,_,_,_,_) ->
    throw(badlist).

postprocess({match,[]},_,_,_,_) ->
    nomatch;
postprocess({match,_},none,_,_,_) ->
    match;
postprocess({match,M},Any,binary,Flat,Uni) ->
    binarify(postprocess({match,M},Any,index,Flat,Uni),Flat);
postprocess({match,M},Any,list,Flat,Uni) ->
    listify(postprocess({match,M},Any,index,Flat,Uni),Flat,Uni);
postprocess({match,M},all,index,_,_) ->
    {match,M};
postprocess({match,M},false,index,_,_) ->
    {match,M};
postprocess({match,M},stripfirst,index,_,_) ->
    {match, [ T || [_|T] <- M ]}.

binarify({match,M},Flat) ->
    {match, [ [ case {I,L} of
		    {-1,0} ->
			<<>>;
		    {SPos,SLen} ->
			<<_:SPos/binary,Res:SLen/binary,_/binary>> = Flat,
			Res
		end || {I,L} <- One ] || One <- M ]}.
listify({match,M},Flat,Uni) ->
    {match, [ [ case {I,L} of
	    {_,0} ->
		[];
	    {SPos,SLen} ->
		case Uni of
		    true ->
			<<_:SPos/binary,Res:SLen/binary,_/binary>> = Flat,
			unicode:characters_to_list(Res,unicode);
		    false ->
			Start = SPos + 1,
			End = SPos + SLen,
			binary_to_list(Flat,Start,End)
		end
	end || {I,L} <- One ] || One <- M ]}.

ubinarify({match,M},Flat) ->
    {match, [ case {I,L} of
		  {-1,0} ->
		      <<>>;
		  {SPos,SLen} ->
		      <<_:SPos/binary,Res:SLen/binary,_/binary>> = Flat,
		      Res
		end || {I,L} <- M ]};
ubinarify(Else,_) ->
    Else.
ulistify({match,M},Flat) ->
    {match, [ case {I,L} of
	    {_,0} ->
		[];
	    {SPos,SLen} ->
		      <<_:SPos/binary,Res:SLen/binary,_/binary>> = Flat,
		      unicode:characters_to_list(Res,unicode)
	      end || {I,L} <- M ]};
ulistify(Else,_) ->
    Else.

process_uparams([global|_T],_RetType) ->
    throw(false);
process_uparams([{capture,Values,Type}|T],_OldType) ->
    process_uparams([{capture,Values}|T],Type);
process_uparams([H|T],Type) ->
    {NL,NType} = process_uparams(T,Type),
    {[H|NL],NType};
process_uparams([],Type) ->
    {[],Type}.


ucompile(RE,Options) ->
    try
	re:compile(unicode:characters_to_binary(RE,unicode),Options)
    catch
	error:AnyError ->
	    {'EXIT',{new_stacktrace,[{Mod,_,L,Loc}|Rest]}} =
		(catch erlang:error(new_stacktrace,
				    [RE,Options])),
	    erlang:raise(error,AnyError,[{Mod,compile,L,Loc}|Rest])
    end.
	

urun(Subject,RE,Options) ->
    try
	urun2(Subject,RE,Options)
    catch
	error:AnyError ->
	    {'EXIT',{new_stacktrace,[{Mod,_,L,Loc}|Rest]}} =
		(catch erlang:error(new_stacktrace,
				    [Subject,RE,Options])),
	    erlang:raise(error,AnyError,[{Mod,run,L,Loc}|Rest])
    end.

urun2(Subject0,RE0,Options0) ->
    {Options,RetType} = case (catch process_uparams(Options0,index)) of
			    {A,B} ->
				{A,B};
			    _ ->
				{Options0,false}
			end,
    Subject = unicode:characters_to_binary(Subject0,unicode),
    RE = case RE0 of
	     BinRE when is_binary(BinRE) ->
		 BinRE;
	     {re_pattern,_,_,_} = ReCompiled ->
		 ReCompiled;
	     ListRE ->
		 unicode:characters_to_binary(ListRE,unicode)
	 end,
    Ret = re:run(Subject,RE,Options),
    case RetType of
	binary ->
	    ubinarify(Ret,Subject);
	list ->
	    ulistify(Ret,Subject);
	_ ->
	    Ret
    end.
	

%% Might be called either with two-tuple (if regexp was already compiled)
%% or with 3-tuple (saving original RE for exceptions
grun(Subject,RE,{Options,NeedClean}) ->
    try
	grun2(Subject,RE,{Options,NeedClean})
    catch
	error:AnyError ->
	    {'EXIT',{new_stacktrace,[{Mod,_,L,Loc}|Rest]}} =
		(catch erlang:error(new_stacktrace,
				    [Subject,RE,Options])),
	    erlang:raise(error,AnyError,[{Mod,run,L,Loc}|Rest])
    end;
grun(Subject,RE,{Options,NeedClean,OrigRE}) ->
    try
	grun2(Subject,RE,{Options,NeedClean})
    catch
	error:AnyError ->
	    {'EXIT',{new_stacktrace,[{Mod,_,L,Loc}|Rest]}} =
		(catch erlang:error(new_stacktrace,
				    [Subject,OrigRE,Options])),
	    erlang:raise(error,AnyError,[{Mod,run,L,Loc}|Rest])
    end.

grun2(Subject,RE,{Options,NeedClean}) ->
    Unicode = check_for_unicode(RE,Options),
    FlatSubject = to_binary(Subject, Unicode),
    do_grun(FlatSubject,Subject,Unicode,RE,{Options,NeedClean}).

do_grun(FlatSubject,Subject,Unicode,RE,{Options0,NeedClean}) ->
    {StrippedOptions, InitialOffset,
     SelectReturn, ConvertReturn} = 
	case (catch 
		  process_parameters(Options0, 0, false, index, NeedClean)) of
	    badlist ->
		erlang:error(badarg,[Subject,RE,Options0]);
	    CorrectReturn ->
		CorrectReturn
	end,
    postprocess(loopexec(FlatSubject,RE,InitialOffset,
			 byte_size(FlatSubject),
			 Unicode,StrippedOptions),
		SelectReturn,ConvertReturn,FlatSubject,Unicode).

loopexec(_,_,X,Y,_,_) when X > Y ->
    {match,[]};
loopexec(Subject,RE,X,Y,Unicode,Options) ->
    case re:run(Subject,RE,[{offset,X}]++Options) of
	nomatch ->
	    {match,[]};
	{match,[{A,B}|More]} ->
	    {match,Rest} = 
		case B>0 of
		    true ->
			loopexec(Subject,RE,A+B,Y,Unicode,Options);
		    false ->
			{match,M} = 
			    case re:run(Subject,RE,[{offset,X},notempty,
						anchored]++Options) of
				nomatch ->
				    {match,[]};
				{match,Other} ->
				    {match,Other}
			    end,
			NewA = case M of 
				   [{_,NStep}|_] when NStep > 0 ->
				       A+NStep;
				   _ ->
				       forward(Subject,A,1,Unicode)
			       end,
			{match,MM} = loopexec(Subject,RE,NewA,Y,
					      Unicode,Options),
			case M of 
			    [] ->
				{match,MM};
			    _ ->
				{match,[M | MM]}
			end
		end,
	    {match,[[{A,B}|More] | Rest]}
    end.
    
forward(_Chal,A,0,_) ->
    A;
forward(_Chal,A,N,false) ->
    A+N;
forward(Chal,A,N,true) ->
    <<_:A/binary,Tl/binary>> = Chal,
    Forw = case Tl of
	       <<1:1,1:1,0:1,_:5,_/binary>>  ->
		   2;
	       <<1:1,1:1,1:1,0:1,_:4,_/binary>>  ->
		   3;
	       <<1:1,1:1,1:1,1:1,0:1,_:3,_/binary>>  ->
		   4;
	       _ ->
		   1
	   end,
    forward(Chal,A+Forw,N-1,true).

copt(caseless) ->
    true;
copt(dollar_endonly) ->
    true;
copt(dotall) ->
    true;
copt(extended) ->
    true;
copt(firstline) ->
    true;
copt(multiline) ->
    true;
copt(no_auto_capture) ->
    true;
copt(dupnames) ->
    true;
copt(ungreedy) ->
    true;
copt(unicode) ->
    true;
copt(_) ->
    false.

%bothopt({newline,_}) ->
%    true;
%bothopt(anchored) ->
%    true;
%bothopt(_) ->
%    false.

runopt(notempty) ->
    true;
runopt(notbol) ->
    true;
runopt(noteol) ->
    true;
runopt({offset,_}) ->
    true;
runopt({capture,_,_}) ->
    true;
runopt({capture,_}) ->
    true;
runopt(global) ->
    true;
runopt(_) ->
    false.

to_binary(Bin, _IsUnicode) when is_binary(Bin) ->
    Bin;
to_binary(Data, true) ->
    unicode:characters_to_binary(Data,unicode);
to_binary(Data, false) ->
    iolist_to_binary(Data).
