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% 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.
-module(couch_rand).
-export([
uniform/0,
uniform/1
]).
-define(MIN_OTP_VERSION_WITH_RAND_MODULE, 18).
has_rand_module() ->
OtpRelease = case erlang:system_info(otp_release) of
% < R15 is excluded by ./configure already
"R15" ++ _OtpVsn -> 15;
"R16" ++ _OtpVsn -> 16;
Release -> list_to_integer(Release)
end,
OtpRelease >= ?MIN_OTP_VERSION_WITH_RAND_MODULE.
uniform() ->
case has_rand_module() of
true -> rand_uniform();
_False -> norand_uniform()
end.
uniform(N) ->
case has_rand_module() of
true -> rand_uniform(N);
_False -> norand_uniform(N)
end.
norand_uniform() ->
maybe_set_random_seed(),
random:uniform().
norand_uniform(N) ->
maybe_set_random_seed(),
random:uniform(N).
maybe_set_random_seed() ->
case get(random_seed) of
undefined ->
{_, Sec, USec} = os:timestamp(),
Seed = {erlang:phash2(self()), Sec, USec},
random:seed(Seed);
_ ->
ok
end.
rand_uniform() ->
rand:uniform().
rand_uniform(N) ->
rand:uniform(N).
|
