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%% @author Bob Ippolito <bob@mochimedia.com>
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%% @copyright 2010 Mochi Media, Inc.
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%%
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%% Permission is hereby granted, free of charge, to any person obtaining a
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%% copy of this software and associated documentation files (the "Software"),
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%% to deal in the Software without restriction, including without limitation
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%% the rights to use, copy, modify, merge, publish, distribute, sublicense,
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%% and/or sell copies of the Software, and to permit persons to whom the
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%% Software is furnished to do so, subject to the following conditions:
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%%
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%% The above copyright notice and this permission notice shall be included in
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%% all copies or substantial portions of the Software.
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%%
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%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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%% THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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%% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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%% DEALINGS IN THE SOFTWARE.
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%% @doc Write newline delimited log files, ensuring that if a truncated
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%% entry is found on log open then it is fixed before writing. Uses
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%% delayed writes and raw files for performance.
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-module(mochilogfile2).
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-author('bob@mochimedia.com').
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-export([open/1, write/2, close/1, name/1]).
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%% @spec open(Name) -> Handle
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%% @doc Open the log file Name, creating or appending as necessary. All data
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%% at the end of the file will be truncated until a newline is found, to
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%% ensure that all records are complete.
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open(Name) ->
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{ok, FD} = file:open(Name, [raw, read, write, delayed_write, binary]),
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fix_log(FD),
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{?MODULE, Name, FD}.
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%% @spec name(Handle) -> string()
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%% @doc Return the path of the log file.
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name({?MODULE, Name, _FD}) ->
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Name.
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%% @spec write(Handle, IoData) -> ok
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%% @doc Write IoData to the log file referenced by Handle.
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write({?MODULE, _Name, FD}, IoData) ->
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ok = file:write(FD, [IoData, $\n]),
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ok.
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%% @spec close(Handle) -> ok
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%% @doc Close the log file referenced by Handle.
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close({?MODULE, _Name, FD}) ->
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ok = file:sync(FD),
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ok = file:close(FD),
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ok.
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fix_log(FD) ->
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{ok, Location} = file:position(FD, eof),
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Seek = find_last_newline(FD, Location),
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{ok, Seek} = file:position(FD, Seek),
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ok = file:truncate(FD),
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ok.
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%% Seek backwards to the last valid log entry
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find_last_newline(_FD, N) when N =< 1 ->
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0;
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find_last_newline(FD, Location) ->
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case file:pread(FD, Location - 1, 1) of
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{ok, <<$\n>>} ->
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Location;
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{ok, _} ->
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find_last_newline(FD, Location - 1)
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end.
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%%
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%% Tests
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%%
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-ifdef(TEST).
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-include_lib("eunit/include/eunit.hrl").
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name_test() ->
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D = mochitemp:mkdtemp(),
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FileName = filename:join(D, "open_close_test.log"),
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H = open(FileName),
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?assertEqual(
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FileName,
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name(H)),
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close(H),
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file:delete(FileName),
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file:del_dir(D),
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ok.
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open_close_test() ->
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D = mochitemp:mkdtemp(),
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FileName = filename:join(D, "open_close_test.log"),
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OpenClose = fun () ->
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H = open(FileName),
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?assertEqual(
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true,
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filelib:is_file(FileName)),
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ok = close(H),
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?assertEqual(
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{ok, <<>>},
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file:read_file(FileName)),
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ok
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end,
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OpenClose(),
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OpenClose(),
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file:delete(FileName),
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file:del_dir(D),
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ok.
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write_test() ->
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D = mochitemp:mkdtemp(),
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FileName = filename:join(D, "write_test.log"),
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F = fun () ->
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H = open(FileName),
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write(H, "test line"),
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close(H),
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ok
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end,
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F(),
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?assertEqual(
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{ok, <<"test line\n">>},
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file:read_file(FileName)),
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F(),
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?assertEqual(
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{ok, <<"test line\ntest line\n">>},
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file:read_file(FileName)),
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file:delete(FileName),
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file:del_dir(D),
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ok.
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fix_log_test() ->
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D = mochitemp:mkdtemp(),
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FileName = filename:join(D, "write_test.log"),
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file:write_file(FileName, <<"first line good\nsecond line bad">>),
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F = fun () ->
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H = open(FileName),
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write(H, "test line"),
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close(H),
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ok
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end,
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F(),
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?assertEqual(
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{ok, <<"first line good\ntest line\n">>},
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file:read_file(FileName)),
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file:write_file(FileName, <<"first line bad">>),
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F(),
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?assertEqual(
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{ok, <<"test line\n">>},
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file:read_file(FileName)),
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F(),
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?assertEqual(
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{ok, <<"test line\ntest line\n">>},
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file:read_file(FileName)),
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ok.
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-endif.
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