143 lines
4.5 KiB
Erlang
143 lines
4.5 KiB
Erlang
%%--------------------------------------------------------------------
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%% Copyright (c) 2019 EMQ Technologies Co., Ltd. All Rights Reserved.
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%%
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%% Licensed under the Apache License, Version 2.0 (the "License");
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%% you may not use this file except in compliance with the License.
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%% You may obtain a copy of the License at
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%%
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%% http://www.apache.org/licenses/LICENSE-2.0
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%%
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%% Unless required by applicable law or agreed to in writing, software
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%% distributed under the License is distributed on an "AS IS" BASIS,
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%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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%% See the License for the specific language governing permissions and
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%% limitations under the License.
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%%--------------------------------------------------------------------
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%% @doc Generate global unique id for mqtt message.
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%%
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%% --------------------------------------------------------
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%% | Timestamp | NodeID + PID | Sequence |
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%% |<------- 64bits ------->|<--- 48bits --->|<- 16bits ->|
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%% --------------------------------------------------------
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%%
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%% 1. Timestamp: erlang:system_time if Erlang >= R18, otherwise os:timestamp
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%% 2. NodeId: encode node() to 2 bytes integer
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%% 3. Pid: encode pid to 4 bytes integer
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%% 4. Sequence: 2 bytes sequence in one process
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%%
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%% @end
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-module(emqx_guid).
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-export([ gen/0
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, new/0
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, timestamp/1
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, to_hexstr/1
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, from_hexstr/1
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, to_base62/1
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, from_base62/1
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]).
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-define(MAX_SEQ, 16#FFFF).
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-type(guid() :: <<_:128>>).
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%% @doc Generate a global unique id.
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-spec(gen() -> guid()).
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gen() ->
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Guid = case get(guid) of
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undefined -> new();
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{_Ts, NPid, Seq} -> next(NPid, Seq)
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end,
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put(guid, Guid), bin(Guid).
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new() ->
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{ts(), npid(), 0}.
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-spec(timestamp(guid()) -> integer()).
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timestamp(<<Ts:64, _/binary>>) ->
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Ts.
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next(NPid, Seq) when Seq >= ?MAX_SEQ ->
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{ts(), NPid, 0};
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next(NPid, Seq) ->
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{ts(), NPid, Seq + 1}.
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bin({Ts, NPid, Seq}) ->
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<<Ts:64, NPid:48, Seq:16>>.
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ts() ->
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case erlang:function_exported(erlang, system_time, 1) of
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true -> %% R18
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erlang:system_time(micro_seconds);
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false ->
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{MegaSeconds, Seconds, MicroSeconds} = os:timestamp(),
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(MegaSeconds * 1000000 + Seconds) * 1000000 + MicroSeconds
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end.
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%% Copied from https://github.com/okeuday/uuid.git.
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npid() ->
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<<NodeD01, NodeD02, NodeD03, NodeD04, NodeD05,
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NodeD06, NodeD07, NodeD08, NodeD09, NodeD10,
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NodeD11, NodeD12, NodeD13, NodeD14, NodeD15,
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NodeD16, NodeD17, NodeD18, NodeD19, NodeD20>> =
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crypto:hash(sha, erlang:list_to_binary(erlang:atom_to_list(node()))),
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% later, when the pid format changes, handle the different format
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ExternalTermFormatVersion = 131,
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PidExtType = 103,
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<<ExternalTermFormatVersion:8,
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PidExtType:8,
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PidBin/binary>> = erlang:term_to_binary(self()),
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% 72 bits for the Erlang pid
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<<PidID1:8, PidID2:8, PidID3:8, PidID4:8, % ID (Node specific, 15 bits)
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PidSR1:8, PidSR2:8, PidSR3:8, PidSR4:8, % Serial (extra uniqueness)
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PidCR1:8 % Node Creation Count
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>> = binary:part(PidBin, erlang:byte_size(PidBin), -9),
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% reduce the 160 bit NodeData checksum to 16 bits
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NodeByte1 = ((((((((NodeD01 bxor NodeD02)
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bxor NodeD03)
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bxor NodeD04)
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bxor NodeD05)
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bxor NodeD06)
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bxor NodeD07)
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bxor NodeD08)
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bxor NodeD09)
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bxor NodeD10,
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NodeByte2 = (((((((((NodeD11 bxor NodeD12)
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bxor NodeD13)
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bxor NodeD14)
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bxor NodeD15)
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bxor NodeD16)
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bxor NodeD17)
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bxor NodeD18)
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bxor NodeD19)
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bxor NodeD20)
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bxor PidCR1,
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% reduce the Erlang pid to 32 bits
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PidByte1 = PidID1 bxor PidSR4,
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PidByte2 = PidID2 bxor PidSR3,
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PidByte3 = PidID3 bxor PidSR2,
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PidByte4 = PidID4 bxor PidSR1,
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<<NPid:48>> = <<NodeByte1:8, NodeByte2:8,
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PidByte1:8, PidByte2:8,
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PidByte3:8, PidByte4:8>>,
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NPid.
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to_hexstr(<<I:128>>) ->
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list_to_binary(integer_to_list(I, 16)).
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from_hexstr(S) ->
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I = list_to_integer(binary_to_list(S), 16), <<I:128>>.
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to_base62(<<I:128>>) ->
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emqx_base62:encode(I).
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from_base62(S) ->
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I = binary_to_integer( emqx_base62:decode(S)),
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<<I:128>>.
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