riak_core_lite

%% Generalized random module that offers a backwards compatible API
%% around some of the changes in rand, crypto and for time units.

-module(riak_core_rand).

%% API
-export([uniform/0, uniform/1, uniform_s/2, seed/0,
         seed/1, rand_seed/0, rand_bytes/1]).

%% As the algorithm is not changed in any place  we can use the default
%% algorithm for all call here.
-define(ALGO, exsplus).

uniform() -> rand:uniform().

uniform(N) -> rand:uniform(N).

%% The old random:uniform_s took a 3 touple however this is no longer
%% the case, so what we need to do if we see such a situation is to first
%% create a state using seed_s (which can take the old data) and then
%% using uniform_s with this newly generated state.
%%
%% Note that seed_s does **not** change the current seed but just
%% create a new seed state.
uniform_s(N, {A, B, C}) ->
    State = rand:seed_s(?ALGO, {A, B, C}),
    rand:uniform_s(N, State);
uniform_s(N, State) -> rand:uniform_s(N, State).

seed() -> rand:seed(?ALGO).

%% We are a bit tricky here, while random:seed did return the **prior** seed
%% rand:seed will return the **new** seed. We can work around this by first
%% getting the exported seed then using this instead.
-spec seed({integer(), integer(), integer()} |
           rand:export_state()) -> rand:export_state() | undefined.

seed({_, _, _} = Seed) ->
    Old = rand:export_seed(),
    _New = rand:seed(?ALGO, Seed),
    Old;
seed(Seed) ->
    Old = rand:export_seed(), _New = rand:seed(Seed), Old.

rand_bytes(Size) -> crypto:strong_rand_bytes(Size).

%%%===================================================================
%%% General functions
%%%===================================================================

rand_seed() -> erlang:timestamp().