snowflake.lua

---
--- Generated by EmmyLua(https://github.com/EmmyLua)
--- Created by ehr.
--- DateTime: 2019/10/12 18:12
---

local LSNOW_FLAKE = {
    _VERSION = "0.0.1"
}

function LSNOW_FLAKE:new(workerid, datacenterid)
    self.worker_id = workerid
    self.data_center_id = datacenterid
    -- stats
    self.ids_generated = 0

    -- Tue, 21 Mar 2006 20:50:14.000 GMT
    self.twepoch = 1142974214000
    self.timeval_ms = 0

    self.sequence = 0
    self.worker_id_bits = 5
    self.data_center_id_bits = 5
    self.max_worker_id = (1 << self.worker_id_bits)
    self.max_data_center_id = (1 << self.data_center_id_bits)
    self.sequence_bits = 12

    self.worker_id_shift = self.sequence_bits
    self.data_center_id_shift = self.sequence_bits + self.worker_id_bits
    self.timestamp_left_shift = self.sequence_bits + self.worker_id_bits + self.data_center_id_bits
    self.sequence_mask = (1 << self.sequence_bits)
    self.last_timestamp = -1

    if self.worker_id > self.max_worker_id or self.worker_id < 0 then
        return nil
    end

    if self.data_center_id > self.max_data_center_id or self.data_center_id < 0 then
        return nil
    end

    return self
end

function LSNOW_FLAKE:_time_gen()
    local ms_val = os.clock() * 1000 - self.timeval_ms * 1000
    return math.modf(os.time() * 1000 + ms_val)
end

function LSNOW_FLAKE:_till_next_millis(last_timestamp)
    timestamp = self:_time_gen()

    while timestamp < last_timestamp do
        timestamp = self:_time_gen()
    end

    return timestamp
end

function LSNOW_FLAKE:get_id()
    timestamp = self:_time_gen()
    --print(timestamp)
    if self.last_timestamp > timestamp then
        return nil
    end

    if self.last_timestamp == timestamp then
        if (self.sequence + 1) > self.sequence_mask then
            self.sequence = 0
        else
            self.sequence = self.sequence + 1
        end

        if self.sequence == 0 then
            timestamp = self:_till_next_millis(self.last_timestamp)
        end
    else
        self.sequence = 0
    end
    self.last_timestamp = timestamp

    local new_id = ((timestamp - self.twepoch) << self.timestamp_left_shift)
            | (self.data_center_id << self.data_center_id_shift)
            | (self.worker_id << self.worker_id_shift)
            | self.sequence


    self.ids_generated = self.ids_generated + 1

    return new_id
end

return LSNOW_FLAKE