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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2014. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+%%
+%% If your code need to be able to execute on ERTS versions both
+%% earlier and later than 7.0, the best approach is to use the new
+%% time API introduced in ERTS 7.0 and implement a fallback
+%% solution using the old primitives to be used on old ERTS
+%% versions. This way your code can automatically take advantage
+%% of the improvements in the API when available. This is an
+%% example of how to implement such an API, but it can be used
+%% as is if you want to. Just add this module to your project,
+%% and call the API via this module instead of calling the
+%% BIFs directly.
+%%
+
+-module(time_compat).
+
+%% We don't want warnings about the use of erlang:now/0 in
+%% this module.
+-compile(nowarn_deprecated_function).
+%%
+%% We don't use
+%% -compile({nowarn_deprecated_function, [{erlang, now, 0}]}).
+%% since this will produce warnings when compiled on systems
+%% where it has not yet been deprecated.
+%%
+
+-export([monotonic_time/0,
+ monotonic_time/1,
+ erlang_system_time/0,
+ erlang_system_time/1,
+ os_system_time/0,
+ os_system_time/1,
+ time_offset/0,
+ time_offset/1,
+ convert_time_unit/3,
+ timestamp/0,
+ unique_integer/0,
+ unique_integer/1,
+ monitor/2,
+ system_info/1,
+ system_flag/2]).
+
+monotonic_time() ->
+ try
+ erlang:monotonic_time()
+ catch
+ error:undef ->
+ %% Use Erlang system time as monotonic time
+ erlang_system_time_fallback()
+ end.
+
+monotonic_time(Unit) ->
+ try
+ erlang:monotonic_time(Unit)
+ catch
+ error:badarg ->
+ erlang:error(badarg, [Unit]);
+ error:undef ->
+ %% Use Erlang system time as monotonic time
+ STime = erlang_system_time_fallback(),
+ try
+ convert_time_unit_fallback(STime, native, Unit)
+ catch
+ error:bad_time_unit -> erlang:error(badarg, [Unit])
+ end
+ end.
+
+erlang_system_time() ->
+ try
+ erlang:system_time()
+ catch
+ error:undef ->
+ erlang_system_time_fallback()
+ end.
+
+erlang_system_time(Unit) ->
+ try
+ erlang:system_time(Unit)
+ catch
+ error:badarg ->
+ erlang:error(badarg, [Unit]);
+ error:undef ->
+ STime = erlang_system_time_fallback(),
+ try
+ convert_time_unit_fallback(STime, native, Unit)
+ catch
+ error:bad_time_unit -> erlang:error(badarg, [Unit])
+ end
+ end.
+
+os_system_time() ->
+ try
+ os:system_time()
+ catch
+ error:undef ->
+ os_system_time_fallback()
+ end.
+
+os_system_time(Unit) ->
+ try
+ os:system_time(Unit)
+ catch
+ error:badarg ->
+ erlang:error(badarg, [Unit]);
+ error:undef ->
+ STime = os_system_time_fallback(),
+ try
+ convert_time_unit_fallback(STime, native, Unit)
+ catch
+ error:bad_time_unit -> erlang:error(badarg, [Unit])
+ end
+ end.
+
+time_offset() ->
+ try
+ erlang:time_offset()
+ catch
+ error:undef ->
+ %% Erlang system time and Erlang monotonic
+ %% time are always aligned
+ 0
+ end.
+
+time_offset(Unit) ->
+ try
+ erlang:time_offset(Unit)
+ catch
+ error:badarg ->
+ erlang:error(badarg, [Unit]);
+ error:undef ->
+ try
+ _ = integer_time_unit(Unit)
+ catch
+ error:bad_time_unit -> erlang:error(badarg, [Unit])
+ end,
+ %% Erlang system time and Erlang monotonic
+ %% time are always aligned
+ 0
+ end.
+
+convert_time_unit(Time, FromUnit, ToUnit) ->
+ try
+ erlang:convert_time_unit(Time, FromUnit, ToUnit)
+ catch
+ error:undef ->
+ try
+ convert_time_unit_fallback(Time, FromUnit, ToUnit)
+ catch
+ _:_ ->
+ erlang:error(badarg, [Time, FromUnit, ToUnit])
+ end;
+ error:Error ->
+ erlang:error(Error, [Time, FromUnit, ToUnit])
+ end.
+
+timestamp() ->
+ try
+ erlang:timestamp()
+ catch
+ error:undef ->
+ erlang:now()
+ end.
+
+unique_integer() ->
+ try
+ erlang:unique_integer()
+ catch
+ error:undef ->
+ {MS, S, US} = erlang:now(),
+ (MS*1000000+S)*1000000+US
+ end.
+
+unique_integer(Modifiers) ->
+ try
+ erlang:unique_integer(Modifiers)
+ catch
+ error:badarg ->
+ erlang:error(badarg, [Modifiers]);
+ error:undef ->
+ case is_valid_modifier_list(Modifiers) of
+ true ->
+ %% now() converted to an integer
+ %% fullfill the requirements of
+ %% all modifiers: unique, positive,
+ %% and monotonic...
+ {MS, S, US} = erlang:now(),
+ (MS*1000000+S)*1000000+US;
+ false ->
+ erlang:error(badarg, [Modifiers])
+ end
+ end.
+
+monitor(Type, Item) ->
+ try
+ erlang:monitor(Type, Item)
+ catch
+ error:Error ->
+ case {Error, Type, Item} of
+ {badarg, time_offset, clock_service} ->
+ %% Time offset is final and will never change.
+ %% Return a dummy reference, there will never
+ %% be any need for 'CHANGE' messages...
+ make_ref();
+ _ ->
+ erlang:error(Error, [Type, Item])
+ end
+ end.
+
+system_info(Item) ->
+ try
+ erlang:system_info(Item)
+ catch
+ error:badarg ->
+ case Item of
+ time_correction ->
+ case erlang:system_info(tolerant_timeofday) of
+ enabled -> true;
+ disabled -> false
+ end;
+ time_warp_mode ->
+ no_time_warp;
+ time_offset ->
+ final;
+ NotSupArg when NotSupArg == os_monotonic_time_source;
+ NotSupArg == start_time ->
+ %% Cannot emulate this...
+ erlang:error(notsup, [NotSupArg]);
+ _ ->
+ erlang:error(badarg, [Item])
+ end;
+ error:Error ->
+ erlang:error(Error, [Item])
+ end.
+
+system_flag(Flag, Value) ->
+ try
+ erlang:system_flag(Flag, Value)
+ catch
+ error:Error ->
+ case {Error, Flag, Value} of
+ {badarg, time_offset, finalize} ->
+ %% Time offset is final
+ final;
+ _ ->
+ erlang:error(Error, [Flag, Value])
+ end
+ end.
+
+%%
+%% Internal functions
+%%
+
+integer_time_unit(native) -> 1000*1000;
+integer_time_unit(nano_seconds) -> 1000*1000*1000;
+integer_time_unit(micro_seconds) -> 1000*1000;
+integer_time_unit(milli_seconds) -> 1000;
+integer_time_unit(seconds) -> 1;
+integer_time_unit(I) when is_integer(I), I > 0 -> I;
+integer_time_unit(BadRes) -> erlang:error(bad_time_unit, [BadRes]).
+
+erlang_system_time_fallback() ->
+ {MS, S, US} = erlang:now(),
+ (MS*1000000+S)*1000000+US.
+
+os_system_time_fallback() ->
+ {MS, S, US} = os:timestamp(),
+ (MS*1000000+S)*1000000+US.
+
+convert_time_unit_fallback(Time, FromUnit, ToUnit) ->
+ FU = integer_time_unit(FromUnit),
+ TU = integer_time_unit(ToUnit),
+ case Time < 0 of
+ true -> TU*Time - (FU - 1);
+ false -> TU*Time
+ end div FU.
+
+is_valid_modifier_list([positive|Ms]) ->
+ is_valid_modifier_list(Ms);
+is_valid_modifier_list([monotonic|Ms]) ->
+ is_valid_modifier_list(Ms);
+is_valid_modifier_list([]) ->
+ true;
+is_valid_modifier_list(_) ->
+ false.