machi/src/machi_plist.erl

69 lines
2 KiB
Erlang

-module(machi_plist).
%%% @doc persistent list of binaries
-export([open/2, close/1, find/2, add/2]).
-ifdef(TEST).
-export([all/1]).
-endif.
-record(machi_plist,
{filename :: file:filename_all(),
fd :: file:io_device(),
list = [] :: list(string)}).
-type plist() :: #machi_plist{}.
-export_type([plist/0]).
-spec open(file:filename_all(), proplists:proplist()) ->
{ok, plist()} | {error, file:posix()}.
open(Filename, _Opt) ->
%% TODO: This decode could fail if the file didn't finish writing
%% whole contents, which should be fixed by some persistent
%% solution.
List = case file:read_file(Filename) of
{ok, <<>>} -> [];
{ok, Bin} -> binary_to_term(Bin);
{error, enoent} -> []
end,
case file:open(Filename, [read, write, raw, binary, sync]) of
{ok, Fd} ->
{ok, #machi_plist{filename=Filename,
fd=Fd,
list=List}};
Error ->
Error
end.
-spec close(plist()) -> ok.
close(#machi_plist{fd=Fd}) ->
_ = file:close(Fd).
-spec find(plist(), string()) -> boolean().
find(#machi_plist{list=List}, Name) ->
lists:member(Name, List).
-spec add(plist(), string()) -> {ok, plist()} | {error, file:posix()}.
add(Plist = #machi_plist{list=List0, fd=Fd}, Name) ->
case find(Plist, Name) of
true ->
{ok, Plist};
false ->
List = lists:append(List0, [Name]),
%% TODO: partial write could break the file with other
%% persistent info (even lose data of trimmed states);
%% needs a solution.
case file:pwrite(Fd, 0, term_to_binary(List)) of
ok ->
{ok, Plist#machi_plist{list=List}};
Error ->
Error
end
end.
-ifdef(TEST).
-spec all(plist()) -> [file:filename()].
all(#machi_plist{list=List}) ->
List.
-endif.