Add time compat module from http://www.erlang.org/doc/apps/erts/time_compat.erl

src/time_compat.erl

@@ -0,0 +1,305 @@
+%%
+%% %CopyrightBegin%
+%% 
+%% Copyright Ericsson AB 2014-2015. All Rights Reserved.
+%% 
+%% 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.
+%% 
+%% %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 (a preferrably renamed version of)
+%% 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 == os_system_time_source;
+			       NotSupArg == start_time;
+			       NotSupArg == end_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.