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@@ -59,8 +59,15 @@
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hexstr_to_bin/1
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]).
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+-export([
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+ nolink_apply/1,
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+ nolink_apply/2
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+]).
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+
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-export([clamp/3]).
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+-dialyzer({nowarn_function, [nolink_apply/2]}).
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+
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-define(SHORT, 8).
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-define(DEFAULT_PMAP_TIMEOUT, 5000).
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@@ -375,29 +382,101 @@ explain_posix(estale) -> "Stale remote file handle";
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explain_posix(exdev) -> "Cross-domain link";
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explain_posix(NotPosix) -> NotPosix.
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--spec pmap(fun((A) -> B), list(A)) -> list(B | {error, term()}).
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+%% @doc Like lists:map/2, only the callback function is evaluated
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+%% concurrently.
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+-spec pmap(fun((A) -> B), list(A)) -> list(B).
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pmap(Fun, List) when is_function(Fun, 1), is_list(List) ->
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pmap(Fun, List, ?DEFAULT_PMAP_TIMEOUT).
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--spec pmap(fun((A) -> B), list(A), timeout()) -> list(B | {error, term()}).
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+-spec pmap(fun((A) -> B), list(A), timeout()) -> list(B).
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pmap(Fun, List, Timeout) when
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is_function(Fun, 1), is_list(List), is_integer(Timeout), Timeout >= 0
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->
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- Self = self(),
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- Pids = lists:map(
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- fun(El) ->
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- spawn_link(
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- fun() -> pmap_exec(Self, Fun, El, Timeout) end
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- )
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- end,
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- List
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+ nolink_apply(fun() -> do_parallel_map(Fun, List) end, Timeout).
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+
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+%% @doc Delegate a function to a worker process.
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+%% The function may spawn_link other processes but we do not
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+%% want the caller process to be linked.
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+%% This is done by isolating the possible link with a not-linked
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+%% middleman process.
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+nolink_apply(Fun) -> nolink_apply(Fun, infinity).
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+
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+%% @doc Same as `nolink_apply/1', with a timeout.
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+-spec nolink_apply(function(), timer:timeout()) -> term().
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+nolink_apply(Fun, Timeout) when is_function(Fun, 0) ->
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+ Caller = self(),
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+ ResRef = make_ref(),
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+ Middleman = erlang:spawn(
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+ fun() ->
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+ process_flag(trap_exit, true),
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+ CallerMRef = erlang:monitor(process, Caller),
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+ Worker = erlang:spawn_link(
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+ fun() ->
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+ Res =
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+ try
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+ {normal, Fun()}
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+ catch
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+ C:E:S ->
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+ {exception, {C, E, S}}
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+ end,
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+ _ = erlang:send(Caller, {ResRef, Res}),
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+ exit(normal)
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+ end
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+ ),
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+ receive
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+ {'DOWN', CallerMRef, process, _, _} ->
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+ %% For whatever reason, if the caller is dead,
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+ %% there is no reason to continue
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+ exit(Worker, kill),
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+ exit(normal);
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+ {'EXIT', Worker, normal} ->
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+ exit(normal);
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+ {'EXIT', Worker, Reason} ->
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+ %% worker exited with some reason other than 'normal'
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+ _ = erlang:send(Caller, {ResRef, {'EXIT', Reason}}),
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+ exit(normal)
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+ end
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+ end
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),
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- pmap_gather(Pids).
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+ receive
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+ {ResRef, {normal, Result}} ->
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+ Result;
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+ {ResRef, {exception, {C, E, S}}} ->
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+ erlang:raise(C, E, S);
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+ {ResRef, {'EXIT', Reason}} ->
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+ exit(Reason)
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+ after Timeout ->
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+ exit(Middleman, kill),
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+ exit(timeout)
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+ end.
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%%------------------------------------------------------------------------------
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%% Internal Functions
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%%------------------------------------------------------------------------------
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+do_parallel_map(Fun, List) ->
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+ Parent = self(),
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+ PidList = lists:map(
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+ fun(Item) ->
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+ erlang:spawn_link(
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+ fun() ->
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+ Parent ! {self(), Fun(Item)}
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+ end
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+ )
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+ end,
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+ List
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+ ),
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+ lists:foldr(
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+ fun(Pid, Acc) ->
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+ receive
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+ {Pid, Result} ->
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+ [Result | Acc]
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+ end
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+ end,
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+ [],
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+ PidList
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+ ).
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+
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int_to_hex(I, N) when is_integer(I), I >= 0 ->
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int_to_hex([], I, 1, N).
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@@ -418,29 +497,6 @@ pad(L, 0) ->
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pad(L, Count) ->
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pad([$0 | L], Count - 1).
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-pmap_gather([Pid | Pids]) ->
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- receive
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- {Pid, Result} -> [Result | pmap_gather(Pids)]
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- end;
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-pmap_gather([]) ->
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- [].
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-
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-pmap_exec(CallerPid, Fun, El, Timeout) ->
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- ExecPid = self(),
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- {Pid, Ref} = spawn_monitor(fun() ->
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- Result = Fun(El),
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- ExecPid ! {result, self(), Result}
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- end),
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- ExecResult =
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- receive
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- {result, Pid, Result} -> Result;
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- {'DOWN', Ref, process, Pid, Reason} -> {error, Reason}
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- after Timeout ->
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- true = erlang:exit(Pid, kill),
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- {error, timeout}
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- end,
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- CallerPid ! {ExecPid, ExecResult}.
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-
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-ifdef(TEST).
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-include_lib("eunit/include/eunit.hrl").
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Zaiming (Stone) Shi