lib/etorrent-1.0/src/etorrent_file_logger.erl

   1 %%%-------------------------------------------------------------------
   2 %%% File    : etorrent_file_logger.erl
   3 %%% Author  : Jesper Louis Andersen <>
   4 %%% Description : Log to a file. Loosely based on log_mf_h from the
   5 %%%  erlang distribution
   6 %%%
   7 %%% Created :  9 Jul 2008 by Jesper Louis Andersen <>
   8 %%%-------------------------------------------------------------------
   9 -module(etorrent_file_logger).
  10
  11 -include("log.hrl").
  12
  13 -behaviour(gen_event).
  14
  15 -export([init/3, init/2]).
  16
  17 -export([init/1, handle_event/2, handle_info/2, terminate/2]).
  18 -export([handle_call/2, code_change/3]).
  19
  20 -record(state, {dir, fname, cur_fd, pred}).
  21
  22 %%%-----------------------------------------------------------------
  23 %%% This module implements an event handler that writes events
  24 %%% to a single logfile.
  25 %%%-----------------------------------------------------------------
  26 %% Func: init/2
  27 %% Args: EventMgr = pid() | atom()
  28 %%       Dir  = string()
  29 %%       Filename  = string()
  30 %%       Pred = fun(Event) -> boolean()
  31 %% Purpose: An event handler.  Writes binary events
  32 %%          to file Filename in the directory Dir.
  33 %%          Each event is filtered with the predicate function Pred.
  34 %%          Reports can be browsed with Report Browser Tool (rb).
  35 %% Returns: Args = term()
  36 %%          The Args term should be used in a call to
  37 %%          gen_event:add_handler(EventMgr, log_mf_h, Args).
  38 %%-----------------------------------------------------------------
  39 init(Dir, Filename) -> init(Dir, Filename, fun(_) -> true end).
  40 init(Dir, Filename, Pred) -> {Dir, Filename, Pred}.
  41
  42 %%-----------------------------------------------------------------
  43 %% Call-back functions from gen_event
  44 %%-----------------------------------------------------------------
  45 init({Dir, Filename, Pred}) ->
  46     case catch file_open(Dir, Filename) of
  47         {ok, Fd} -> {ok, #state { dir = Dir, fname = Filename,
  48                                   cur_fd = Fd, pred = Pred }};
  49         Error -> Error
  50     end.
  51
  52 handle_event(Event, S) ->
  53     Date = date_str(erlang:localtime()),
  54         #state{dir = _Dir, fname = _Fname, cur_fd = _CurFd, pred = Pred} = S,
  55         case catch Pred(Event) of
  56         true ->
  57         io:format(S#state.cur_fd, "~s : ~p~n", [Date, Event]),
  58                 {ok, S};
  59         _ ->
  60         {ok, S}
  61         end.
  62
  63 handle_info(_, State) ->
  64     {ok, State}.
  65
  66 terminate(_, State) ->
  67     case file:close(State#state.cur_fd) of
  68         ok -> State;
  69         {error, R} -> ?log([cant_close_file,{reason, R}]), State
  70     end.
  71
  72 handle_call(null, State) ->
  73     {ok, null, State}.
  74
  75 code_change(_OldVsn, State, _Extra) ->
  76     {ok, State}.
  77
  78 %%-----------------------------------------------------------------
  79 %% Misc functions
  80 %%-----------------------------------------------------------------
  81 file_open(Dir, Fname) ->
  82     {ok, FD} = file:open(filename:join(Dir, Fname), [append]),
  83     {ok, FD}.
  84
  85 date_str({{Y, Mo, D}, {H, Mi, S}}) ->
  86     lists:flatten(io_lib:format("~w-~2.2.0w-~2.2.0w ~2.2.0w:"
  87                                 "~2.2.0w:~2.2.0w",
  88                                 [Y,Mo,D,H,Mi,S])).