Clean up code for file:position/2

2 files changed, 46 insertions, 31 deletions

diff --git a/lib/kernel/src/file_io_server.erl b/lib/kernel/src/file_io_server.erl
index d0ad43afbf..5b2cae6b02 100644
--- a/lib/kernel/src/file_io_server.erl
+++ b/lib/kernel/src/file_io_server.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2000-2013. All Rights Reserved.
+%% Copyright Ericsson AB 2000-2015. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -217,23 +217,23 @@ file_request({allocate, Offset, Length},
 file_request({pread,At,Sz}, 
 	     #state{handle=Handle,buf=Buf,read_mode=ReadMode}=State) ->
     case position(Handle, At, Buf) of
-	{ok,_Offs} ->
+	{error,_} = Reply ->
+	    {error,Reply,State};
+	_ ->
 	    case ?PRIM_FILE:read(Handle, Sz) of
 		{ok,Bin} when ReadMode =:= list ->
 		    std_reply({ok,binary_to_list(Bin)}, State);
 		Reply ->
 		    std_reply(Reply, State)
-	    end;
-	Reply ->
-	    std_reply(Reply, State)
+	    end
     end;
 file_request({pwrite,At,Data}, 
 	     #state{handle=Handle,buf=Buf}=State) ->
     case position(Handle, At, Buf) of
-	{ok,_Offs} ->
-	    std_reply(?PRIM_FILE:write(Handle, Data), State);
-	Reply ->
-	    std_reply(Reply, State)
+	{error,_} = Reply ->
+	    {error,Reply,State};
+	_ ->
+	    std_reply(?PRIM_FILE:write(Handle, Data), State)
     end;
 file_request(datasync,
 	     #state{handle=Handle}=State) ->
@@ -257,10 +257,10 @@ file_request(close,
 file_request({position,At}, 
 	     #state{handle=Handle,buf=Buf}=State) ->
     case position(Handle, At, Buf) of
-    {error, _Reason}=Reply ->
-        {error,Reply,State};
-    Reply ->
-        {reply,Reply,State#state{buf= <<>>}}
+	{error,_} = Reply ->
+	    {error,Reply,State};
+	Reply ->
+	    std_reply(Reply, State)
     end;
 file_request(truncate, 
 	     #state{handle=Handle}=State) ->
@@ -268,13 +268,14 @@ file_request(truncate,
 	{error,_Reason}=Reply ->
 	    {stop,normal,Reply,State#state{buf= <<>>}};
 	Reply ->
-	    {reply,Reply,State}
+	    std_reply(Reply, State)
     end;
 file_request(Unknown, 
 	     #state{}=State) ->
     Reason = {request, Unknown},
     {error,{error,Reason},State}.
 
+%% Standard reply and clear buffer
 std_reply({error,_}=Reply, State) ->
     {error,Reply,State#state{buf= <<>>}};
 std_reply(Reply, State) ->
@@ -291,7 +292,7 @@ io_request({put_chars, Enc, Chars},
 	   #state{handle=Handle,buf=Buf}=State) ->
     case position(Handle, cur, Buf) of
 	{error,_}=Reply ->
-	    {stop,normal,Reply,State#state{buf= <<>>}};
+	    {stop,normal,Reply,State};
 	_ ->
 	    put_chars(Chars, Enc, State#state{buf= <<>>})
     end;
@@ -372,23 +373,27 @@ io_request_loop([Request|Tail],
 %% I/O request put_chars
 %%
 put_chars(Chars, latin1, #state{handle=Handle, unic=latin1}=State) ->
+    NewState = State#state{buf = <<>>},
     case ?PRIM_FILE:write(Handle, Chars) of
 	{error,_}=Reply ->
-	    {stop,normal,Reply,State};
+	    {stop,normal,Reply,NewState};
 	Reply ->
-	    {reply,Reply,State}
+	    {reply,Reply,NewState}
     end;
 put_chars(Chars, InEncoding, #state{handle=Handle, unic=OutEncoding}=State) ->
+    NewState = State#state{buf = <<>>},
     case unicode:characters_to_binary(Chars,InEncoding,OutEncoding) of
 	Bin when is_binary(Bin) ->
 	    case ?PRIM_FILE:write(Handle, Bin) of
 		{error,_}=Reply ->
-		    {stop,normal,Reply,State};
+		    {stop,normal,Reply,NewState};
 		Reply ->
-		    {reply,Reply,State}
+		    {reply,Reply,NewState}
 	    end;
 	{error,_,_} ->
-	    {stop,normal,{error,{no_translation, InEncoding, OutEncoding}},State}
+	    {stop,normal,
+	     {error,{no_translation, InEncoding, OutEncoding}},
+	     NewState}
     end.
 
 %%
@@ -902,11 +907,14 @@ cbv({utf32,little},_) ->
 
 %% Compensates ?PRIM_FILE:position/2 for the number of bytes 
 %% we have buffered
-
-position(Handle, cur, Buf) ->
-    position(Handle, {cur, 0}, Buf);
-position(Handle, {cur, Offs}, Buf) when is_binary(Buf) ->
-    ?PRIM_FILE:position(Handle, {cur, Offs-byte_size(Buf)});
-position(Handle, At, _Buf) ->
-    ?PRIM_FILE:position(Handle, At).
-
+position(Handle, At, Buf) ->
+    ?PRIM_FILE:position(
+       Handle,
+       case At of
+	   cur ->
+	       {cur, -byte_size(Buf)};
+	   {cur, Offs} ->
+	       {cur, Offs-byte_size(Buf)};
+	   _ ->
+	       At
+       end).
diff --git a/lib/kernel/test/file_SUITE.erl b/lib/kernel/test/file_SUITE.erl
index 2911635db7..e9300bf019 100644
--- a/lib/kernel/test/file_SUITE.erl
+++ b/lib/kernel/test/file_SUITE.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2013. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2015. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -130,7 +130,7 @@ groups() ->
       [open1, old_modes, new_modes, path_open, close, access,
        read_write, pread_write, append, open_errors,
        exclusive]},
-     {pos, [], [pos1, pos2]},
+     {pos, [], [pos1, pos2, pos3]},
      {file_info, [],
       [file_info_basic_file, file_info_basic_directory,
        file_info_bad, file_info_times, file_write_file_info]},
@@ -1220,7 +1220,7 @@ pos2(Config) when is_list(Config) ->
     ok.
 
 pos3(suite) -> [];
-pos3(doc) -> ["When it does not use raw mode, file:postiion had a bug."];
+pos3(doc) -> ["When it does not use raw mode, file:position had a bug."];
 pos3(Config) when is_list(Config) ->
     ?line Dog = test_server:timetrap(test_server:seconds(5)),
     ?line RootDir = ?config(data_dir, Config),
@@ -1229,8 +1229,15 @@ pos3(Config) when is_list(Config) ->
     ?line {ok, Fd} = ?FILE_MODULE:open(Name, [read, binary]),
     ?line {ok, _}  = ?FILE_MODULE:read(Fd, 5),
     ?line {error, einval} = ?FILE_MODULE:position(Fd, {bof, -1}),
+
     %% Here ok had returned =(
     ?line {error, einval} = ?FILE_MODULE:position(Fd, {cur, -10}),
+    %% That test is actually questionable since file:position/2
+    %% is documented to leave the file position undefined after
+    %% it has returned an error.  But on Posix systems the position
+    %% is guaranteed to be unchanged after an error return.  On e.g
+    %% Windows there is nothing stated about this in the documentation.
+
     ?line test_server:timetrap_cancel(Dog),
     ok.