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+%% @author Bob Ippolito <bob@mochimedia.com>
+%% @copyright 2008 Mochi Media, Inc.
+
+%% @doc String Formatting for Erlang, inspired by Python 2.6
+%% (<a href="http://www.python.org/dev/peps/pep-3101/">PEP 3101</a>).
+%%
+-module(mochifmt).
+-author('bob@mochimedia.com').
+-export([format/2, format_field/2, convert_field/2, get_value/2, get_field/2]).
+-export([tokenize/1, format/3, get_field/3, format_field/3]).
+-export([bformat/2, bformat/3]).
+-export([f/2, f/3]).
+
+-record(conversion, {length, precision, ctype, align, fill_char, sign}).
+
+%% @spec tokenize(S::string()) -> tokens()
+%% @doc Tokenize a format string into mochifmt's internal format.
+tokenize(S) ->
+ {?MODULE, tokenize(S, "", [])}.
+
+%% @spec convert_field(Arg, Conversion::conversion()) -> term()
+%% @doc Process Arg according to the given explicit conversion specifier.
+convert_field(Arg, "") ->
+ Arg;
+convert_field(Arg, "r") ->
+ repr(Arg);
+convert_field(Arg, "s") ->
+ str(Arg).
+
+%% @spec get_value(Key::string(), Args::args()) -> term()
+%% @doc Get the Key from Args. If Args is a tuple then convert Key to
+%% an integer and get element(1 + Key, Args). If Args is a list and Key
+%% can be parsed as an integer then use lists:nth(1 + Key, Args),
+%% otherwise try and look for Key in Args as a proplist, converting
+%% Key to an atom or binary if necessary.
+get_value(Key, Args) when is_tuple(Args) ->
+ element(1 + list_to_integer(Key), Args);
+get_value(Key, Args) when is_list(Args) ->
+ try lists:nth(1 + list_to_integer(Key), Args)
+ catch error:_ ->
+ {_K, V} = proplist_lookup(Key, Args),
+ V
+ end.
+
+%% @spec get_field(Key::string(), Args) -> term()
+%% @doc Consecutively call get_value/2 on parts of Key delimited by ".",
+%% replacing Args with the result of the previous get_value. This
+%% is used to implement formats such as {0.0}.
+get_field(Key, Args) ->
+ get_field(Key, Args, ?MODULE).
+
+%% @spec get_field(Key::string(), Args, Module) -> term()
+%% @doc Consecutively call Module:get_value/2 on parts of Key delimited by ".",
+%% replacing Args with the result of the previous get_value. This
+%% is used to implement formats such as {0.0}.
+get_field(Key, Args, Module) ->
+ {Name, Next} = lists:splitwith(fun (C) -> C =/= $. end, Key),
+ Res = try Module:get_value(Name, Args)
+ catch error:undef -> get_value(Name, Args) end,
+ case Next of
+ "" ->
+ Res;
+ "." ++ S1 ->
+ get_field(S1, Res, Module)
+ end.
+
+%% @spec format(Format::string(), Args) -> iolist()
+%% @doc Format Args with Format.
+format(Format, Args) ->
+ format(Format, Args, ?MODULE).
+
+%% @spec format(Format::string(), Args, Module) -> iolist()
+%% @doc Format Args with Format using Module.
+format({?MODULE, Parts}, Args, Module) ->
+ format2(Parts, Args, Module, []);
+format(S, Args, Module) ->
+ format(tokenize(S), Args, Module).
+
+%% @spec format_field(Arg, Format) -> iolist()
+%% @doc Format Arg with Format.
+format_field(Arg, Format) ->
+ format_field(Arg, Format, ?MODULE).
+
+%% @spec format_field(Arg, Format, _Module) -> iolist()
+%% @doc Format Arg with Format.
+format_field(Arg, Format, _Module) ->
+ F = default_ctype(Arg, parse_std_conversion(Format)),
+ fix_padding(fix_sign(convert2(Arg, F), F), F).
+
+%% @spec f(Format::string(), Args) -> string()
+%% @doc Format Args with Format and return a string().
+f(Format, Args) ->
+ f(Format, Args, ?MODULE).
+
+%% @spec f(Format::string(), Args, Module) -> string()
+%% @doc Format Args with Format using Module and return a string().
+f(Format, Args, Module) ->
+ case lists:member(${, Format) of
+ true ->
+ binary_to_list(bformat(Format, Args, Module));
+ false ->
+ Format
+ end.
+
+%% @spec bformat(Format::string(), Args) -> binary()
+%% @doc Format Args with Format and return a binary().
+bformat(Format, Args) ->
+ iolist_to_binary(format(Format, Args)).
+
+%% @spec bformat(Format::string(), Args, Module) -> binary()
+%% @doc Format Args with Format using Module and return a binary().
+bformat(Format, Args, Module) ->
+ iolist_to_binary(format(Format, Args, Module)).
+
+%% Internal API
+
+add_raw("", Acc) ->
+ Acc;
+add_raw(S, Acc) ->
+ [{raw, lists:reverse(S)} | Acc].
+
+tokenize([], S, Acc) ->
+ lists:reverse(add_raw(S, Acc));
+tokenize("{{" ++ Rest, S, Acc) ->
+ tokenize(Rest, "{" ++ S, Acc);
+tokenize("{" ++ Rest, S, Acc) ->
+ {Format, Rest1} = tokenize_format(Rest),
+ tokenize(Rest1, "", [{format, make_format(Format)} | add_raw(S, Acc)]);
+tokenize("}}" ++ Rest, S, Acc) ->
+ tokenize(Rest, "}" ++ S, Acc);
+tokenize([C | Rest], S, Acc) ->
+ tokenize(Rest, [C | S], Acc).
+
+tokenize_format(S) ->
+ tokenize_format(S, 1, []).
+
+tokenize_format("}" ++ Rest, 1, Acc) ->
+ {lists:reverse(Acc), Rest};
+tokenize_format("}" ++ Rest, N, Acc) ->
+ tokenize_format(Rest, N - 1, "}" ++ Acc);
+tokenize_format("{" ++ Rest, N, Acc) ->
+ tokenize_format(Rest, 1 + N, "{" ++ Acc);
+tokenize_format([C | Rest], N, Acc) ->
+ tokenize_format(Rest, N, [C | Acc]).
+
+make_format(S) ->
+ {Name0, Spec} = case lists:splitwith(fun (C) -> C =/= $: end, S) of
+ {_, ""} ->
+ {S, ""};
+ {SN, ":" ++ SS} ->
+ {SN, SS}
+ end,
+ {Name, Transform} = case lists:splitwith(fun (C) -> C =/= $! end, Name0) of
+ {_, ""} ->
+ {Name0, ""};
+ {TN, "!" ++ TT} ->
+ {TN, TT}
+ end,
+ {Name, Transform, Spec}.
+
+proplist_lookup(S, P) ->
+ A = try list_to_existing_atom(S)
+ catch error:_ -> make_ref() end,
+ B = try list_to_binary(S)
+ catch error:_ -> make_ref() end,
+ proplist_lookup2({S, A, B}, P).
+
+proplist_lookup2({KS, KA, KB}, [{K, V} | _])
+ when KS =:= K orelse KA =:= K orelse KB =:= K ->
+ {K, V};
+proplist_lookup2(Keys, [_ | Rest]) ->
+ proplist_lookup2(Keys, Rest).
+
+format2([], _Args, _Module, Acc) ->
+ lists:reverse(Acc);
+format2([{raw, S} | Rest], Args, Module, Acc) ->
+ format2(Rest, Args, Module, [S | Acc]);
+format2([{format, {Key, Convert, Format0}} | Rest], Args, Module, Acc) ->
+ Format = f(Format0, Args, Module),
+ V = case Module of
+ ?MODULE ->
+ V0 = get_field(Key, Args),
+ V1 = convert_field(V0, Convert),
+ format_field(V1, Format);
+ _ ->
+ V0 = try Module:get_field(Key, Args)
+ catch error:undef -> get_field(Key, Args, Module) end,
+ V1 = try Module:convert_field(V0, Convert)
+ catch error:undef -> convert_field(V0, Convert) end,
+ try Module:format_field(V1, Format)
+ catch error:undef -> format_field(V1, Format, Module) end
+ end,
+ format2(Rest, Args, Module, [V | Acc]).
+
+default_ctype(_Arg, C=#conversion{ctype=N}) when N =/= undefined ->
+ C;
+default_ctype(Arg, C) when is_integer(Arg) ->
+ C#conversion{ctype=decimal};
+default_ctype(Arg, C) when is_float(Arg) ->
+ C#conversion{ctype=general};
+default_ctype(_Arg, C) ->
+ C#conversion{ctype=string}.
+
+fix_padding(Arg, #conversion{length=undefined}) ->
+ Arg;
+fix_padding(Arg, F=#conversion{length=Length, fill_char=Fill0, align=Align0,
+ ctype=Type}) ->
+ Padding = Length - iolist_size(Arg),
+ Fill = case Fill0 of
+ undefined ->
+ $\s;
+ _ ->
+ Fill0
+ end,
+ Align = case Align0 of
+ undefined ->
+ case Type of
+ string ->
+ left;
+ _ ->
+ right
+ end;
+ _ ->
+ Align0
+ end,
+ case Padding > 0 of
+ true ->
+ do_padding(Arg, Padding, Fill, Align, F);
+ false ->
+ Arg
+ end.
+
+do_padding(Arg, Padding, Fill, right, _F) ->
+ [lists:duplicate(Padding, Fill), Arg];
+do_padding(Arg, Padding, Fill, center, _F) ->
+ LPadding = lists:duplicate(Padding div 2, Fill),
+ RPadding = case Padding band 1 of
+ 1 ->
+ [Fill | LPadding];
+ _ ->
+ LPadding
+ end,
+ [LPadding, Arg, RPadding];
+do_padding([$- | Arg], Padding, Fill, sign_right, _F) ->
+ [[$- | lists:duplicate(Padding, Fill)], Arg];
+do_padding(Arg, Padding, Fill, sign_right, #conversion{sign=$-}) ->
+ [lists:duplicate(Padding, Fill), Arg];
+do_padding([S | Arg], Padding, Fill, sign_right, #conversion{sign=S}) ->
+ [[S | lists:duplicate(Padding, Fill)], Arg];
+do_padding(Arg, Padding, Fill, sign_right, #conversion{sign=undefined}) ->
+ [lists:duplicate(Padding, Fill), Arg];
+do_padding(Arg, Padding, Fill, left, _F) ->
+ [Arg | lists:duplicate(Padding, Fill)].
+
+fix_sign(Arg, #conversion{sign=$+}) when Arg >= 0 ->
+ [$+, Arg];
+fix_sign(Arg, #conversion{sign=$\s}) when Arg >= 0 ->
+ [$\s, Arg];
+fix_sign(Arg, _F) ->
+ Arg.
+
+ctype($\%) -> percent;
+ctype($s) -> string;
+ctype($b) -> bin;
+ctype($o) -> oct;
+ctype($X) -> upper_hex;
+ctype($x) -> hex;
+ctype($c) -> char;
+ctype($d) -> decimal;
+ctype($g) -> general;
+ctype($f) -> fixed;
+ctype($e) -> exp.
+
+align($<) -> left;
+align($>) -> right;
+align($^) -> center;
+align($=) -> sign_right.
+
+convert2(Arg, F=#conversion{ctype=percent}) ->
+ [convert2(100.0 * Arg, F#conversion{ctype=fixed}), $\%];
+convert2(Arg, #conversion{ctype=string}) ->
+ str(Arg);
+convert2(Arg, #conversion{ctype=bin}) ->
+ erlang:integer_to_list(Arg, 2);
+convert2(Arg, #conversion{ctype=oct}) ->
+ erlang:integer_to_list(Arg, 8);
+convert2(Arg, #conversion{ctype=upper_hex}) ->
+ erlang:integer_to_list(Arg, 16);
+convert2(Arg, #conversion{ctype=hex}) ->
+ string:to_lower(erlang:integer_to_list(Arg, 16));
+convert2(Arg, #conversion{ctype=char}) when Arg < 16#80 ->
+ [Arg];
+convert2(Arg, #conversion{ctype=char}) ->
+ xmerl_ucs:to_utf8(Arg);
+convert2(Arg, #conversion{ctype=decimal}) ->
+ integer_to_list(Arg);
+convert2(Arg, #conversion{ctype=general, precision=undefined}) ->
+ try mochinum:digits(Arg)
+ catch error:undef -> io_lib:format("~g", [Arg]) end;
+convert2(Arg, #conversion{ctype=fixed, precision=undefined}) ->
+ io_lib:format("~f", [Arg]);
+convert2(Arg, #conversion{ctype=exp, precision=undefined}) ->
+ io_lib:format("~e", [Arg]);
+convert2(Arg, #conversion{ctype=general, precision=P}) ->
+ io_lib:format("~." ++ integer_to_list(P) ++ "g", [Arg]);
+convert2(Arg, #conversion{ctype=fixed, precision=P}) ->
+ io_lib:format("~." ++ integer_to_list(P) ++ "f", [Arg]);
+convert2(Arg, #conversion{ctype=exp, precision=P}) ->
+ io_lib:format("~." ++ integer_to_list(P) ++ "e", [Arg]).
+
+str(A) when is_atom(A) ->
+ atom_to_list(A);
+str(I) when is_integer(I) ->
+ integer_to_list(I);
+str(F) when is_float(F) ->
+ try mochinum:digits(F)
+ catch error:undef -> io_lib:format("~g", [F]) end;
+str(L) when is_list(L) ->
+ L;
+str(B) when is_binary(B) ->
+ B;
+str(P) ->
+ repr(P).
+
+repr(P) when is_float(P) ->
+ try mochinum:digits(P)
+ catch error:undef -> float_to_list(P) end;
+repr(P) ->
+ io_lib:format("~p", [P]).
+
+parse_std_conversion(S) ->
+ parse_std_conversion(S, #conversion{}).
+
+parse_std_conversion("", Acc) ->
+ Acc;
+parse_std_conversion([Fill, Align | Spec], Acc)
+ when Align =:= $< orelse Align =:= $> orelse Align =:= $= orelse Align =:= $^ ->
+ parse_std_conversion(Spec, Acc#conversion{fill_char=Fill,
+ align=align(Align)});
+parse_std_conversion([Align | Spec], Acc)
+ when Align =:= $< orelse Align =:= $> orelse Align =:= $= orelse Align =:= $^ ->
+ parse_std_conversion(Spec, Acc#conversion{align=align(Align)});
+parse_std_conversion([Sign | Spec], Acc)
+ when Sign =:= $+ orelse Sign =:= $- orelse Sign =:= $\s ->
+ parse_std_conversion(Spec, Acc#conversion{sign=Sign});
+parse_std_conversion("0" ++ Spec, Acc) ->
+ Align = case Acc#conversion.align of
+ undefined ->
+ sign_right;
+ A ->
+ A
+ end,
+ parse_std_conversion(Spec, Acc#conversion{fill_char=$0, align=Align});
+parse_std_conversion(Spec=[D|_], Acc) when D >= $0 andalso D =< $9 ->
+ {W, Spec1} = lists:splitwith(fun (C) -> C >= $0 andalso C =< $9 end, Spec),
+ parse_std_conversion(Spec1, Acc#conversion{length=list_to_integer(W)});
+parse_std_conversion([$. | Spec], Acc) ->
+ case lists:splitwith(fun (C) -> C >= $0 andalso C =< $9 end, Spec) of
+ {"", Spec1} ->
+ parse_std_conversion(Spec1, Acc);
+ {P, Spec1} ->
+ parse_std_conversion(Spec1,
+ Acc#conversion{precision=list_to_integer(P)})
+ end;
+parse_std_conversion([Type], Acc) ->
+ parse_std_conversion("", Acc#conversion{ctype=ctype(Type)}).
+
+
+%%
+%% Tests
+%%
+-include_lib("eunit/include/eunit.hrl").
+-ifdef(TEST).
+
+tokenize_test() ->
+ {?MODULE, [{raw, "ABC"}]} = tokenize("ABC"),
+ {?MODULE, [{format, {"0", "", ""}}]} = tokenize("{0}"),
+ {?MODULE, [{raw, "ABC"}, {format, {"1", "", ""}}, {raw, "DEF"}]} =
+ tokenize("ABC{1}DEF"),
+ ok.
+
+format_test() ->
+ <<" -4">> = bformat("{0:4}", [-4]),
+ <<" 4">> = bformat("{0:4}", [4]),
+ <<" 4">> = bformat("{0:{0}}", [4]),
+ <<"4 ">> = bformat("{0:4}", ["4"]),
+ <<"4 ">> = bformat("{0:{0}}", ["4"]),
+ <<"1.2yoDEF">> = bformat("{2}{0}{1}{3}", {yo, "DE", 1.2, <<"F">>}),
+ <<"cafebabe">> = bformat("{0:x}", {16#cafebabe}),
+ <<"CAFEBABE">> = bformat("{0:X}", {16#cafebabe}),
+ <<"CAFEBABE">> = bformat("{0:X}", {16#cafebabe}),
+ <<"755">> = bformat("{0:o}", {8#755}),
+ <<"a">> = bformat("{0:c}", {97}),
+ %% Horizontal ellipsis
+ <<226, 128, 166>> = bformat("{0:c}", {16#2026}),
+ <<"11">> = bformat("{0:b}", {3}),
+ <<"11">> = bformat("{0:b}", [3]),
+ <<"11">> = bformat("{three:b}", [{three, 3}]),
+ <<"11">> = bformat("{three:b}", [{"three", 3}]),
+ <<"11">> = bformat("{three:b}", [{<<"three">>, 3}]),
+ <<"\"foo\"">> = bformat("{0!r}", {"foo"}),
+ <<"2008-5-4">> = bformat("{0.0}-{0.1}-{0.2}", {{2008,5,4}}),
+ <<"2008-05-04">> = bformat("{0.0:04}-{0.1:02}-{0.2:02}", {{2008,5,4}}),
+ <<"foo6bar-6">> = bformat("foo{1}{0}-{1}", {bar, 6}),
+ <<"-'atom test'-">> = bformat("-{arg!r}-", [{arg, 'atom test'}]),
+ <<"2008-05-04">> = bformat("{0.0:0{1.0}}-{0.1:0{1.1}}-{0.2:0{1.2}}",
+ {{2008,5,4}, {4, 2, 2}}),
+ ok.
+
+std_test() ->
+ M = mochifmt_std:new(),
+ <<"01">> = bformat("{0}{1}", [0, 1], M),
+ ok.
+
+records_test() ->
+ M = mochifmt_records:new([{conversion, record_info(fields, conversion)}]),
+ R = #conversion{length=long, precision=hard, sign=peace},
+ long = M:get_value("length", R),
+ hard = M:get_value("precision", R),
+ peace = M:get_value("sign", R),
+ <<"long hard">> = bformat("{length} {precision}", R, M),
+ <<"long hard">> = bformat("{0.length} {0.precision}", [R], M),
+ ok.
+
+-endif.