1 files changed, 75 insertions, 0 deletions
diff --git a/lib/kernel/src/raw_file_io.erl b/lib/kernel/src/raw_file_io.erl
new file mode 100644
index 0000000000..e3c07c8f78
--- /dev/null
+++ b/lib/kernel/src/raw_file_io.erl
@@ -0,0 +1,75 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2017. 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(raw_file_io).
+
+-export([open/2]).
+
+open(Filename, Modes) ->
+    %% Layers are applied in this order, and the listed modules will call this
+    %% function again as necessary. eg. a raw compressed delayed file in list
+    %% mode will walk through [_list -> _compressed -> _delayed -> _raw].
+    ModuleOrder = [{raw_file_io_list, fun match_list/1},
+                   {raw_file_io_compressed, fun match_compressed/1},
+                   {raw_file_io_delayed, fun match_delayed/1},
+                   {raw_file_io_raw, fun match_raw/1}],
+    open_1(ModuleOrder, Filename, add_implicit_modes(Modes)).
+open_1([], _Filename, _Modes) ->
+    error(badarg);
+open_1([{Module, Match} | Rest], Filename, Modes) ->
+    case lists:any(Match, Modes) of
+        true ->
+            {Options, ChildModes} =
+                lists:partition(fun(Mode) -> Match(Mode) end, Modes),
+            Module:open_layer(Filename, ChildModes, Options);
+        false ->
+            open_1(Rest, Filename, Modes)
+    end.
+
+%% 'read' and 'list' mode are enabled unless disabled by another option, so
+%% we'll explicitly add them to avoid duplicating this logic in child layers.
+add_implicit_modes(Modes0) ->
+    Modes1 = add_unless_matched(Modes0, fun match_writable/1, read),
+    add_unless_matched(Modes1, fun match_binary/1, list).
+add_unless_matched(Modes, Match, Default) ->
+    case lists:any(Match, Modes) of
+        false -> [Default | Modes];
+        true -> Modes
+    end.
+
+match_list(list) -> true;
+match_list(_Other) -> false.
+
+match_compressed(compressed) -> true;
+match_compressed(_Other) -> false.
+
+match_delayed({delayed_write, _Size, _Timeout}) -> true;
+match_delayed(delayed_write) -> true;
+match_delayed(_Other) -> false.
+
+match_raw(raw) -> true;
+match_raw(_Other) -> false.
+
+match_writable(write) -> true;
+match_writable(append) -> true;
+match_writable(exclusive) -> true;
+match_writable(_Other) -> false.
+
+match_binary(binary) -> true;
+match_binary(_Other) -> false.