add exists to ec_file

Signed-off-by: Jordan Wilberding <diginux@gmail.com>

src/ec_file.erl

@@ -7,6 +7,7 @@
 -module(ec_file).
 
 -export([
+         exists/1,
          copy/2,
          copy/3,
          insecure_mkdtemp/0,
@@ -40,6 +41,15 @@
 %%%===================================================================
 %%% API
 %%%===================================================================
+-spec exists(file:filename()) -> boolean().
+exists(Filename) ->
+    case file:read_file_info(Filename) of
+        {ok, _}         ->
+            true;
+        {error, _Reason} ->
+            false
+    end.
+
 %% @doc copy an entire directory to another location.
 -spec copy(file:name(), file:name(), Options::[option()]) -> ok | {error, Reason::term()}.
 copy(From, To, []) ->
@@ -314,6 +324,16 @@ setup_base_and_target() ->
     ok = file:write_file(NoName, DummyContents),
     {BaseDir, SourceDir, {Name1, Name2, Name3, NoName}}.
 
+exists_test() ->
+    BaseDir = insecure_mkdtemp(),
+    SourceDir = filename:join([BaseDir, "source1"]),
+    NoName = filename:join([SourceDir, "noname"]),
+    ok = file:make_dir(SourceDir),
+    Name1 = filename:join([SourceDir, "fileone"]),
+    ok = file:write_file(Name1, <<"Testn">>),
+    ?assertMatch(true, exists(Name1)),
+    ?assertMatch(false, exists(NoName)).
+
 find_test() ->
     %% Create a directory in /tmp for the test. Clean everything afterwards
     {BaseDir, _SourceDir, {Name1, Name2, Name3, _NoName}} = setup_base_and_target(),