1 files changed, 95 insertions, 0 deletions
diff --git a/apps/couch/src/couch_uuids.erl b/apps/couch/src/couch_uuids.erl
new file mode 100644
index 00000000..e1851e1d
--- /dev/null
+++ b/apps/couch/src/couch_uuids.erl
@@ -0,0 +1,95 @@
+% 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.