1 files changed, 71 insertions, 0 deletions
diff --git a/src/cowboy_iolists.erl b/src/cowboy_iolists.erl
new file mode 100644
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+++ b/src/cowboy_iolists.erl
@@ -0,0 +1,71 @@
+%% Copyright (c) 2017, Loïc Hoguin <[email protected]>
+%%
+%% 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(cowboy_iolists).
+
+-export([split/2]).
+
+-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} ->
+			{ok, Before, [After|Tail]};
+		{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!", ""}
+	],
+	[{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].
+
+-endif.