Initial commit

Makefile

@@ -0,0 +1,27 @@
+CWD=$(shell pwd)
+NAME=$(shell basename ${CWD})
+CT_LOG=${APP_DIR}/logs
+REBAR?=${CWD}/rebar
+COOKIE?=cookie_${NAME}
+ERL?=/usr/bin/env erl
+ERLARGS=-pa ebin -smp enable -name ${NODE} \
+	-setcookie ${COOKIE} -boot start_sasl
+
+all: clean compile
+
+# Clean all.
+clean:
+	@${REBAR} clean
+
+# Gets dependencies.
+getdeps:
+	@${REBAR} get-deps
+
+# Compiles.
+compile:
+	@${REBAR} compile
+
+# This one runs without a release.
+shell: compile
+	${ERL} ${ERLARGS}
+

rebar.config

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+{erl_opts, [
+  {src_dirs, ["src"]},
+  warn_unused_vars,
+  warn_export_all,
+  warn_shadow_vars,
+  warn_unused_import,
+  warn_unused_function,
+  warn_bif_clash,
+  warn_unused_record,
+  warn_deprecated_function,
+  warn_obsolete_guard,
+  strict_validation,
+  warn_export_vars,
+  warn_exported_vars,
+  warn_missing_spec,
+  warn_untyped_record,
+  debug_info
+]}.
+{ct_extra_params, "-no_auto_compile -dir ebin"}.
+{cover_enabled, true}.
+{eunit_opts, [verbose, {skip_deps, true}]}.
+{eunit_exclude_deps, true}.
+{cover_enabled, true}.
+{xref_warnings, true}.
+{xref_checks, [
+  undefined_function_calls,
+  undefined_functions,
+  locals_not_used,
+  deprecated_function_calls,
+  deprecated_functions
+]}.

src/simple_cache.app.src

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+{application, simple_cache, [
+  {description, "Small simple cache using ETS"},
+  {vsn, "git"},
+  {registered, []},
+  {applications, [kernel, stdlib]},
+  {mod, { simple_cache, []}},
+  {env, []}
+ ]}.

src/simple_cache.erl

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+%%% @doc Main module for simple_cache.
+%%%
+%%% Copyright 2013 Marcelo Gornstein <marcelog@@gmail.com>
+%%%
+%%% 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.
+%%% @end
+%%% @copyright Marcelo Gornstein <marcelog@gmail.com>
+%%% @author Marcelo Gornstein <marcelog@gmail.com>
+%%%
+-module(simple_cache).
+-author('marcelog@gmail.com').
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Types.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+-define(ETS_TID, atom_to_list(?MODULE)).
+-define(NAME(N), list_to_atom(?ETS_TID ++ "_" ++ atom_to_list(N))).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Exports.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% Public API.
+-export([init/1]).
+-export([get/4]).
+-export([flush/1, flush/2]).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Public API.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% @doc Initializes a cache.
+-spec init(string()) -> ok.
+init(CacheName) ->
+  RealName = ?NAME(CacheName),
+  RealName = ets:new(RealName, [
+    named_table, {read_concurrency, true}, public, {write_concurrency, true}
+  ]),
+  ok.
+
+%% @doc Deletes the keys that match the given ets:matchspec() from the cache.
+-spec flush(string(), term()) -> true.
+flush(CacheName, Key) ->
+  RealName = ?NAME(CacheName),
+  ets:delete(RealName, Key).
+
+%% @doc Deletes all keys in the given cache.
+-spec flush(string()) -> true.
+flush(CacheName) ->
+  RealName = ?NAME(CacheName),
+  true = ets:delete_all_objects(RealName).
+
+%% @doc Tries to lookup Key in the cache, and execute the given FunResult
+%% on a miss.
+-spec get(string(), infinity|pos_integer(), term(), function()) -> term().
+get(CacheName, LifeTime, Key, FunResult) ->
+  RealName = ?NAME(CacheName),
+  case ets:lookup(RealName, Key) of
+    [] ->
+      % Not found, create it.
+      create_value(RealName, LifeTime, Key, FunResult);
+    [{Key, R, _CreatedTime, infinity}] -> R; % Found, wont expire, return the value.
+    [{Key, R, CreatedTime, LifeTime}] ->
+      TimeElapsed = now_usecs() - CreatedTime,
+      if
+        TimeElapsed > (LifeTime * 1000) ->
+          % expired? create a new value
+          create_value(RealName, LifeTime, Key, FunResult);
+        true -> R % Not expired, return it.
+      end
+  end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Private API.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% @doc Creates a cache entry.
+-spec create_value(string(), pos_integer(), term(), function()) -> term().
+create_value(RealName, LifeTime, Key, FunResult) ->
+  R = FunResult(),
+  ets:insert(RealName, {Key, R, now_usecs(), LifeTime}),
+  R.
+
+%% @doc Returns total amount of microseconds since 1/1/1.
+-spec now_usecs() -> pos_integer().
+now_usecs() ->
+  {MegaSecs, Secs, MicroSecs} = os:timestamp(),
+  MegaSecs * 1000000000000 + Secs * 1000000 + MicroSecs.