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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_uuids).
-include("couch_db.hrl").
-behaviour(gen_server).
-export([start/0, stop/0]).
-export([new/0, random/0, utc_random/0]).
-export([init/1, terminate/2, code_change/3]).
-export([handle_call/3, handle_cast/2, handle_info/2]).
start() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
stop() ->
gen_server:cast(?MODULE, stop).
new() ->
gen_server:call(?MODULE, create).
random() ->
list_to_binary(couch_util:to_hex(crypto:rand_bytes(16))).
utc_random() ->
Now = {_, _, Micro} = now(),
Nowish = calendar:now_to_universal_time(Now),
Nowsecs = calendar:datetime_to_gregorian_seconds(Nowish),
Then = calendar:datetime_to_gregorian_seconds({{1970, 1, 1}, {0, 0, 0}}),
Prefix = io_lib:format("~14.16.0b", [(Nowsecs - Then) * 1000000 + Micro]),
list_to_binary(Prefix ++ couch_util:to_hex(crypto:rand_bytes(9))).
init([]) ->
ok = couch_config:register(
fun("uuids", _) -> gen_server:cast(?MODULE, change) end
),
{ok, state()}.
terminate(_Reason, _State) ->
ok.
handle_call(create, _From, random) ->
{reply, random(), random};
handle_call(create, _From, utc_random) ->
{reply, utc_random(), utc_random};
handle_call(create, _From, {sequential, Pref, Seq}) ->
Result = ?l2b(Pref ++ io_lib:format("~6.16.0b", [Seq])),
case Seq >= 16#fff000 of
true ->
{reply, Result, {sequential, new_prefix(), inc()}};
_ ->
{reply, Result, {sequential, Pref, Seq + inc()}}
end.
handle_cast(change, _State) ->
{noreply, state()};
handle_cast(stop, State) ->
{stop, normal, State};
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info(_Info, State) ->
{noreply, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
new_prefix() ->
couch_util:to_hex((crypto:rand_bytes(13))).
inc() ->
crypto:rand_uniform(1, 16#ffe).
state() ->
AlgoStr = couch_config:get("uuids", "algorithm", "random"),
case couch_util:to_existing_atom(AlgoStr) of
random ->
random;
utc_random ->
utc_random;
sequential ->
{sequential, new_prefix(), inc()};
Unknown ->
throw({unknown_uuid_algorithm, Unknown})
end.
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