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Diffstat (limited to 'src/mochiweb/mochiglobal.erl')
-rw-r--r-- | src/mochiweb/mochiglobal.erl | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/src/mochiweb/mochiglobal.erl b/src/mochiweb/mochiglobal.erl new file mode 100644 index 00000000..c740b878 --- /dev/null +++ b/src/mochiweb/mochiglobal.erl @@ -0,0 +1,107 @@ +%% @author Bob Ippolito <bob@mochimedia.com> +%% @copyright 2010 Mochi Media, Inc. +%% @doc Abuse module constant pools as a "read-only shared heap" (since erts 5.6) +%% <a href="http://www.erlang.org/pipermail/erlang-questions/2009-March/042503.html">[1]</a>. +-module(mochiglobal). +-author("Bob Ippolito <bob@mochimedia.com>"). +-export([get/1, get/2, put/2, delete/1]). + +-spec get(atom()) -> any() | undefined. +%% @equiv get(K, undefined) +get(K) -> + get(K, undefined). + +-spec get(atom(), T) -> any() | T. +%% @doc Get the term for K or return Default. +get(K, Default) -> + get(K, Default, key_to_module(K)). + +get(_K, Default, Mod) -> + try Mod:term() + catch error:undef -> + Default + end. + +-spec put(atom(), any()) -> ok. +%% @doc Store term V at K, replaces an existing term if present. +put(K, V) -> + put(K, V, key_to_module(K)). + +put(_K, V, Mod) -> + Bin = compile(Mod, V), + code:purge(Mod), + code:load_binary(Mod, atom_to_list(Mod) ++ ".erl", Bin), + ok. + +-spec delete(atom()) -> boolean(). +%% @doc Delete term stored at K, no-op if non-existent. +delete(K) -> + delete(K, key_to_module(K)). + +delete(_K, Mod) -> + code:purge(Mod), + code:delete(Mod). + +-spec key_to_module(atom()) -> atom(). +key_to_module(K) -> + list_to_atom("mochiglobal:" ++ atom_to_list(K)). + +-spec compile(atom(), any()) -> binary(). +compile(Module, T) -> + {ok, Module, Bin} = compile:forms(forms(Module, T), + [verbose, report_errors]), + Bin. + +-spec forms(atom(), any()) -> [erl_syntax:syntaxTree()]. +forms(Module, T) -> + [erl_syntax:revert(X) || X <- term_to_abstract(Module, term, T)]. + +-spec term_to_abstract(atom(), atom(), any()) -> [erl_syntax:syntaxTree()]. +term_to_abstract(Module, Getter, T) -> + [%% -module(Module). + erl_syntax:attribute( + erl_syntax:atom(module), + [erl_syntax:atom(Module)]), + %% -export([Getter/0]). + erl_syntax:attribute( + erl_syntax:atom(export), + [erl_syntax:list( + [erl_syntax:arity_qualifier( + erl_syntax:atom(Getter), + erl_syntax:integer(0))])]), + %% Getter() -> T. + erl_syntax:function( + erl_syntax:atom(Getter), + [erl_syntax:clause([], none, [erl_syntax:abstract(T)])])]. + +%% +%% Tests +%% +-include_lib("eunit/include/eunit.hrl"). +-ifdef(TEST). +get_put_delete_test() -> + K = '$$test$$mochiglobal', + delete(K), + ?assertEqual( + bar, + get(K, bar)), + try + ?MODULE:put(K, baz), + ?assertEqual( + baz, + get(K, bar)), + ?MODULE:put(K, wibble), + ?assertEqual( + wibble, + ?MODULE:get(K)) + after + delete(K) + end, + ?assertEqual( + bar, + get(K, bar)), + ?assertEqual( + undefined, + ?MODULE:get(K)), + ok. +-endif. |