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@@ -68,6 +68,11 @@
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last/1,
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table/1, table/2]).
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+%% Environment handling
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+-export([get_env/3, get_env/4,
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+ get_set_env/3, get_set_env/4,
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+ set_env/5]).
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+
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%% Convenience functions
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-export([add_local_name/1,
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add_global_name/1,
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@@ -269,7 +274,201 @@ lookup_local_counters(P) -> lookup_values({c,l,P}).
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%%
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lookup_global_counters(P) -> lookup_values({c,g,P}).
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+%% @spec get_env(Scope::scope(), App::atom(), Key::atom()) -> term()
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+%% @equiv get_env(Scope, App, Key, [app_env])
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+get_env(Scope, App, Key) ->
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+ get_env(Scope, App, Key, [app_env]).
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+
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+%% @spec (Scope::scope(), App::atom(), Key::atom(), Strategy) -> term()
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+%% Strategy = [Alternative]
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+%% Alternative = app_env
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+%% | os_env
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+%% | inherit | {inherit, pid()}
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+%% | {default, term()}
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+%% | error
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+%% @doc Fetch an environment value, potentially cached as a `gproc_env' property.
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+%%
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+%% This function first tries to read the value of a cached property,
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+%% `{p, Scope, {gproc_env, App, Key}}'. If this fails, it will try the provided
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+%% alternative strategy. `Strategy' is a list of alternatives, tried in order.
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+%% Each alternative can be one of:
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+%%
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+%% * `app_env' - try `application:get_env(App, Key)'
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+%% * `os_env' - try `os:getenv(ENV)', where `ENV' is `Key' converted into an
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+%% uppercase string
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+%% * `{os_env, ENV}' - try `os:getenv(ENV)'
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+%% * `inherit' - inherit the cached value, if any, held by the (proc_lib) parent.
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+%% * `{inherit, Pid}' - inherit the cached value, if any, held by `Pid'.
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+%% * `{default, Value}' - set a default value to return once alternatives have been
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+%% exhausted; if not set, `undefined' will be returned.
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+%% * `error' - raise an exception, `erlang:error(gproc_env, [App, Key, Scope])'.
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+%%
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+%% While any alternative can occur more than once, the only one that might make
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+%% sense to repeat is `{default, Value}'. The last instance will be the one that
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+%% determines the return value.
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+%%
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+%% The `error' option can be used to assert that a value has been previously
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+%% cached. Alternatively, it can be used to assert that a value is either cached
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+%% or at least defined somewhere, e.g. `get_env(l, mnesia, dir, [app_env, error])'.
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+%% @end
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+get_env(Scope, App, Key, Strategy)
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+ when Scope==l, is_atom(App), is_atom(Key);
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+ Scope==g, is_atom(App), is_atom(Key) ->
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+ do_get_env(Scope, App, Key, Strategy, false).
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+
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+%% @spec get_set_env(Scope::scope(), App::atom(), Key::atom()) -> term()
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+%% @equiv get_set_env(Scope, App, Key, [app_env])
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+get_set_env(Scope, App, Key) ->
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+ get_set_env(Scope, App, Key, [app_env]).
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+
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+%% @spec get_set_env(Scope::scope(), App::atom(), Key::atom(), Strategy) -> Value
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+%% @doc Fetch and cache an environment value, if not already cached.
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+%%
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+%% @see get_env/4.
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+%% This function does the same thing as {@link get_env/4}, but also updates the
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+%% cache. Note that the cache will be updated even if the result of the lookup
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+%% is `undefined'.
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+%% @end
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+%%
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+get_set_env(Scope, App, Key, Strategy)
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+ when Scope==l, is_atom(App), is_atom(Key);
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+ Scope==g, is_atom(App), is_atom(Key) ->
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+ do_get_env(Scope, App, Key, Strategy, true).
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+
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+do_get_env(Context, App, Key, Alternatives, Set) ->
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+ case lookup_env(Context, App, Key, self()) of
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+ undefined ->
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+ check_alternatives(Alternatives, Context, App, Key, undefined, Set);
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+ {ok, Value} ->
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+ Value
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+ end.
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+
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+%% @spec set_env(Scope::scope(), App::atom(),
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+%% Key::atom(), Value::term(), Strategy) -> Value
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+%% Strategy = [Alternative]
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+%% Alternative = app_env | os_env | {os_env, VAR}
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+%%
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+%% @doc Updates the cached value as well as underlying environment.
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+%%
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+%% This function should be exercised with caution, as it affects the larger
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+%% environment outside gproc. This function modifies the cached value, and then
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+%% proceeds to update the underlying environment (OS environment variable or
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+%% application environment variable).
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+%% @end
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+%%
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+set_env(Scope, App, Key, Value, Strategy)
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+ when Scope==l, is_atom(App), is_atom(Key);
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+ Scope==g, is_atom(App), is_atom(Key) ->
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+ case is_valid_set_strategy(Strategy, Value) of
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+ true ->
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+ cache_env(Scope, App, Key, Value),
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+ set_strategy(Strategy, App, Key, Value);
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+ false ->
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+ erlang:error(badarg)
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+ end.
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+
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+check_alternatives([{default, Val}|Alts], Scope, App, Key, _, Set) ->
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+ check_alternatives(Alts, Scope, App, Key, Val, Set);
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+check_alternatives([H|T], Scope, App, Key, Def, Set) ->
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+ case try_alternative(H, App, Key, Scope) of
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+ undefined ->
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+ check_alternatives(T, Scope, App, Key, Def, Set);
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+ {ok, Value} ->
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+ if Set ->
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+ cache_env(Scope, App, Key, Value),
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+ Value;
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+ true ->
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+ Value
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+ end
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+ end;
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+check_alternatives([], Scope, App, Key, Def, Set) ->
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+ if Set ->
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+ cache_env(Scope, App, Key, Def);
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+ true ->
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+ ok
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+ end,
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+ Def.
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+
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+try_alternative(error, App, Key, Scope) ->
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+ erlang:error(gproc_env, [App, Key, Scope]);
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+try_alternative(inherit, App, Key, Scope) ->
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+ case get('$ancestors') of
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+ [P|_] ->
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+ lookup_env(Scope, App, Key, P);
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+ _ ->
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+ undefined
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+ end;
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+try_alternative({inherit, P}, App, Key, Scope) ->
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+ lookup_env(Scope, App, Key, P);
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+try_alternative(app_env, App, Key, _Scope) ->
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+ case application:get_env(App, Key) of
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+ undefined -> undefined;
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+ {ok, undefined} -> undefined;
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+ {ok, Value} -> {ok, Value}
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+ end;
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+try_alternative(os_env, _App, Key, _) ->
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+ case os:getenv(os_env_key(Key)) of
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+ "" -> undefined;
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+ Val -> {ok, Val}
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+ end;
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+try_alternative({os_env, Key}, _, _, _) ->
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+ case os:getenv(Key) of
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+ "" -> undefined;
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+ Val -> {ok, Val}
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+ end;
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+try_alternative({mnesia,Type,Key,Pos}, _, _, _) ->
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+ case mnesia:activity(Type, fun() -> mnesia:read(Key) end) of
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+ [] -> undefined;
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+ [Found] ->
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+ {ok, element(Pos, Found)}
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+ end.
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+
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+os_env_key(Key) ->
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+ string:to_upper(atom_to_list(Key)).
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+
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+lookup_env(Scope, App, Key, P) ->
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+ case ets:lookup(?TAB, {{p, Scope, {gproc_env, App, Key}}, P}) of
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+ [] ->
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+ undefined;
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+ [{_, _, Value}] ->
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+ {ok, Value}
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+ end.
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+cache_env(Scope, App, Key, Value) ->
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+ reg({p, Scope, {gproc_env, App, Key}}, Value).
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+
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+is_valid_set_strategy([os_env|T], Value) ->
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+ is_string(Value) andalso is_valid_set_strategy(T, Value);
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+is_valid_set_strategy([{os_env, _}|T], Value) ->
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+ is_string(Value) andalso is_valid_set_strategy(T, Value);
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+is_valid_set_strategy([app_env|T], Value) ->
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+ is_valid_set_strategy(T, Value);
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+is_valid_set_strategy([], _) ->
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+ true;
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+is_valid_set_strategy(_, _) ->
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+ false.
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+
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+set_strategy([H|T], App, Key, Value) ->
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+ case H of
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+ app_env ->
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+ application:set_env(App, Key, Value);
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+ os_env ->
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+ os:putenv(os_env_key(Key), Value);
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+ {os_env, ENV} ->
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+ os:putenv(ENV, Value)
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+ end,
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+ set_strategy(T, App, Key, Value);
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+set_strategy([], _, _, Value) ->
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+ Value.
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+
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+is_string(S) ->
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+ try begin _ = iolist_to_binary(S),
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+ true
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+ end
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+ catch
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+ error:_ ->
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+ false
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+ end.
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%% @spec reg(Key::key()) -> true
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%%
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@@ -472,9 +671,6 @@ local_mreg(T, [_|_] = KVL) ->
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{true,_} -> monitor_me()
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end.
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-
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-
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-
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%% @spec (Key :: key(), Value) -> true
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%% @doc Sets the value of the registeration entry given by Key
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%%
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@@ -507,9 +703,6 @@ set_value({c,l,_} = Key, Value) when is_integer(Value) ->
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set_value(_, _) ->
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erlang:error(badarg).
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-
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-
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-
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%% @spec (Key) -> Value
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%% @doc Read the value stored with a key registered to the current process.
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%%
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@@ -605,9 +798,6 @@ my_is_process_alive(_) ->
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%% remote pid - assume true (too costly to find out)
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true.
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-
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-
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-
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%% @spec (Key::key()) -> [{pid(), Value}]
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%%
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%% @doc Retrieve the `{Pid,Value}' pairs corresponding to Key.
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@@ -625,8 +815,6 @@ lookup_values({T,_,_} = Key) ->
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end,
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[Pair || {P,_} = Pair <- L, my_is_process_alive(P)].
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-
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-
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%% @spec (Key::key(), Incr::integer()) -> integer()
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%%
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%% @doc Updates the counter registered as Key for the current process.
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Ulf Wiger