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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 Abuse module constant pools as a "read-only shared heap" (since erts 5.6)
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%% <a href="http://www.erlang.org/pipermail/erlang-questions/2009-March/042503.html">[1]</a>.
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-module(mochiglobal).
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-author("Bob Ippolito <bob@mochimedia.com>").
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-export([get/1, get/2, put/2, delete/1]).
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-spec get(atom()) -> any() | undefined.
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%% @equiv get(K, undefined)
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get(K) ->
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get(K, undefined).
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-spec get(atom(), T) -> any() | T.
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%% @doc Get the term for K or return Default.
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get(K, Default) ->
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get(K, Default, key_to_module(K)).
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get(_K, Default, Mod) ->
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try Mod:term()
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catch error:undef ->
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Default
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end.
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-spec put(atom(), any()) -> ok.
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%% @doc Store term V at K, replaces an existing term if present.
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put(K, V) ->
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put(K, V, key_to_module(K)).
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put(_K, V, Mod) ->
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Bin = compile(Mod, V),
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code:purge(Mod),
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{module, Mod} = code:load_binary(Mod, atom_to_list(Mod) ++ ".erl", Bin),
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ok.
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-spec delete(atom()) -> boolean().
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%% @doc Delete term stored at K, no-op if non-existent.
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delete(K) ->
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delete(K, key_to_module(K)).
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delete(_K, Mod) ->
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code:purge(Mod),
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code:delete(Mod).
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-spec key_to_module(atom()) -> atom().
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key_to_module(K) ->
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list_to_atom("mochiglobal:" ++ atom_to_list(K)).
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-spec compile(atom(), any()) -> binary().
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compile(Module, T) ->
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{ok, Module, Bin} = compile:forms(forms(Module, T),
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[verbose, report_errors]),
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Bin.
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-spec forms(atom(), any()) -> [erl_syntax:syntaxTree()].
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forms(Module, T) ->
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[erl_syntax:revert(X) || X <- term_to_abstract(Module, term, T)].
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-spec term_to_abstract(atom(), atom(), any()) -> [erl_syntax:syntaxTree()].
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term_to_abstract(Module, Getter, T) ->
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[%% -module(Module).
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erl_syntax:attribute(
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erl_syntax:atom(module),
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[erl_syntax:atom(Module)]),
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%% -export([Getter/0]).
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erl_syntax:attribute(
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erl_syntax:atom(export),
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[erl_syntax:list(
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[erl_syntax:arity_qualifier(
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erl_syntax:atom(Getter),
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erl_syntax:integer(0))])]),
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%% Getter() -> T.
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erl_syntax:function(
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erl_syntax:atom(Getter),
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[erl_syntax:clause([], none, [erl_syntax:abstract(T)])])].
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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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get_put_delete_test() ->
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K = '$$test$$mochiglobal',
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delete(K),
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?assertEqual(
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bar,
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get(K, bar)),
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try
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?MODULE:put(K, baz),
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?assertEqual(
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baz,
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get(K, bar)),
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?MODULE:put(K, wibble),
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?assertEqual(
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wibble,
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?MODULE:get(K))
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after
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delete(K)
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end,
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?assertEqual(
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bar,
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get(K, bar)),
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?assertEqual(
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undefined,
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?MODULE:get(K)),
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ok.
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-endif.
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