Import cow_iolists from Cowboy

ebin/cowlib.app

@@ -1,7 +1,7 @@
 {application, 'cowlib', [
 	{description, "Support library for manipulating Web protocols."},
 	{vsn, "2.3.0"},
-	{modules, ['cow_base64url','cow_cookie','cow_date','cow_hpack','cow_http','cow_http2','cow_http_hd','cow_http_te','cow_mimetypes','cow_multipart','cow_qs','cow_spdy','cow_sse','cow_uri','cow_ws']},
+	{modules, ['cow_base64url','cow_cookie','cow_date','cow_hpack','cow_http','cow_http2','cow_http_hd','cow_http_te','cow_iolists','cow_mimetypes','cow_multipart','cow_qs','cow_spdy','cow_sse','cow_uri','cow_ws']},
 	{registered, []},
 	{applications, [kernel,stdlib,crypto]},
 	{env, []}

src/cow_iolists.erl

@@ -0,0 +1,100 @@
+%% Copyright (c) 2017, Loïc Hoguin <essen@ninenines.eu>
+%%
+%% Permission to use, copy, modify, and/or distribute this software for any
+%% purpose with or without fee is hereby granted, provided that the above
+%% copyright notice and this permission notice appear in all copies.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+-module(cow_iolists).
+
+-export([split/2]).
+
+-ifdef(TEST).
+-include_lib("proper/include/proper.hrl").
+-endif.
+
+-spec split(non_neg_integer(), iodata()) -> {iodata(), iodata()}.
+split(N, Iolist) ->
+	case split(N, Iolist, []) of
+		{ok, Before, After} ->
+			{Before, After};
+		{more, _, Before} ->
+			{lists:reverse(Before), <<>>}
+	end.
+
+split(0, Rest, Acc) ->
+	{ok, lists:reverse(Acc), Rest};
+split(N, [], Acc) ->
+	{more, N, Acc};
+split(N, Binary, Acc) when byte_size(Binary) =< N ->
+	{ok, lists:reverse([Binary|Acc]), <<>>};
+split(N, Binary, Acc) when is_binary(Binary) ->
+	<< Before:N/binary, After/bits >> = Binary,
+	{ok, lists:reverse([Before|Acc]), After};
+split(N, [Binary|Tail], Acc) when byte_size(Binary) =< N ->
+	split(N - byte_size(Binary), Tail, [Binary|Acc]);
+split(N, [Binary|Tail], Acc) when is_binary(Binary) ->
+	<< Before:N/binary, After/bits >> = Binary,
+	{ok, lists:reverse([Before|Acc]), [After|Tail]};
+split(N, [Char|Tail], Acc) when is_integer(Char) ->
+	split(N - 1, Tail, [Char|Acc]);
+split(N, [List|Tail], Acc0) ->
+	case split(N, List, Acc0) of
+		{ok, Before, After} ->
+			IolistSize = iolist_size(Before),
+			if
+				IolistSize < N ->
+					split(N - IolistSize, [After|Tail], lists:reverse(Before));
+				true ->
+					{ok, Before, [After|Tail]}
+			end;
+		{more, More, Acc} ->
+			split(More, Tail, Acc)
+	end.
+
+-ifdef(TEST).
+
+split_test_() ->
+	Tests = [
+		{10, "Hello world!", "Hello worl", "d!"},
+		{10, <<"Hello world!">>, "Hello worl", "d!"},
+		{10, ["He", [<<"llo">>], $\s, [["world"], <<"!">>]], "Hello worl", "d!"},
+		{10, ["Hello "|<<"world!">>], "Hello worl", "d!"},
+		{10, "Hello!", "Hello!", ""},
+		{10, <<"Hello!">>, "Hello!", ""},
+		{10, ["He", [<<"ll">>], $o, [["!"]]], "Hello!", ""},
+		{10, ["Hel"|<<"lo!">>], "Hello!", ""},
+		{10, [[<<>>|<<>>], [], <<"Hello world!">>], "Hello worl", "d!"},
+		{10, [[<<"He">>|<<"llo">>], [$\s], <<"world!">>], "Hello worl", "d!"}
+	],
+	[{iolist_to_binary(V), fun() ->
+		{B, A} = split(N, V),
+		true = iolist_to_binary(RB) =:= iolist_to_binary(B),
+		true = iolist_to_binary(RA) =:= iolist_to_binary(A)
+	end} || {N, V, RB, RA} <- Tests].
+
+prop_split_test() ->
+	?FORALL({N, Input},
+		{non_neg_integer(), iolist()},
+		begin
+			Size = iolist_size(Input),
+			{Before, After} = split(N, Input),
+			if
+				N >= Size ->
+					((iolist_size(After) =:= 0)
+						andalso iolist_to_binary(Before) =:= iolist_to_binary(Input));
+				true ->
+					<<ExpectBefore:N/binary, ExpectAfter/bits>> = iolist_to_binary(Input),
+					(ExpectBefore =:= iolist_to_binary(Before))
+						andalso (ExpectAfter =:= iolist_to_binary(After))
+			end
+		end).
+
+-endif.