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Zotonic standard library

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zotonic_stdlib src z_tempfile.erl
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src/z_tempfile.erl 

%% @author Marc Worrell <marc@worrell.nl>

%% @copyright 2011 Marc Worrell

%% @doc Simple temporary file handling, deletes the file when the calling process stops or crashes.



%% Copyright 2010 Marc Worrell

%%

%% Licensed under the Apache License, Version 2.0 (the "License");

%% you may not use this file except in compliance with the License.

%% You may obtain a copy of the License at

%% 

%%     http://www.apache.org/licenses/LICENSE-2.0

%% 

%% Unless required by applicable law or agreed to in writing, software

%% distributed under the License is distributed on an "AS IS" BASIS,

%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

%% See the License for the specific language governing permissions and

%% limitations under the License.



-module(z_tempfile).

-author("Marc Worrell <marc@worrell.nl>").



-export([

	new/0,

	new/1,

	tempfile/0,

	tempfile/1,

	is_tempfile/1,

	temppath/0

]).



-type filename() :: string().



%% @doc Return a new unique filename, start a monitoring process to clean it up after use.

-spec new() -> filename().

new() ->

	new("").



%% @doc Return a new unique filename, start a monitoring process to clean it up after use.

-spec new(string()) -> filename().

new(Extension) ->

	Filename = tempfile(Extension),

	OwnerPid = self(),

	Pid = erlang:spawn_link(fun() -> cleanup(Filename, OwnerPid) end),

	receive

		{is_monitoring, Pid} -> Filename

	end.





%% @doc Monitoring process, delete file when requesting process stops or crashes

cleanup(Filename, OwnerPid) ->

	process_flag(trap_exit, true),

	MRef = erlang:monitor(process, OwnerPid),

	OwnerPid ! {is_monitoring, self()},

	receive

		{'EXIT', OwnerPid, _Reason} ->

			erlang:demonitor(MRef),

			file:delete(Filename);

		{'DOWN', _MRef, process, OwnerPid, _Reason} ->

			file:delete(Filename)

	end.



%% @doc return a unique temporary filename.

-spec tempfile() -> filename().

tempfile() ->

	tempfile("").



%% @doc return a unique temporary filename with a set extension.

-spec tempfile(string()) -> filename().

tempfile(Extension) ->

	A = crypto:rand_uniform(1,100000000),

	B = crypto:rand_uniform(1,100000000),

    Filename = filename:join(temppath(), lists:flatten(io_lib:format("ztmp-~s-~p.~p~s",[node(),A,B,Extension]))),

    case filelib:is_file(Filename) of

    	true -> tempfile(Extension);

    	false -> Filename

    end.



%% @doc Check if the file is a temporary filename.

-spec is_tempfile(filename()) -> boolean().

is_tempfile(Filename) ->

	lists:prefix(filename:join(temppath(), "ztmp-"), Filename). 



%% @doc Returns the path where to store temporary files.

-spec temppath() -> filename().

temppath() ->

    lists:foldl(fun(false, Fallback) -> Fallback;

                   (Good, _) -> Good end,

                "/tmp",

                [os:getenv("TMP"), os:getenv("TEMP")]).