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use std::time::{SystemTime, UNIX_EPOCH};
const WORKER_ID_BITS: i64 = 5;
const DATACENTER_ID_BITS: i64 = 5;
const SEQUENCE_BITS: i64 = 12;
const MAX_WORKER_ID: i64 = -1 ^ (-1 << WORKER_ID_BITS);
const MAX_DATACENTER_ID: i64 = -1 ^ (-1 << DATACENTER_ID_BITS);
const WORKER_ID_SHIFT: i64 = SEQUENCE_BITS;
const DATACENTER_ID_SHIFT: i64 = SEQUENCE_BITS + WORKER_ID_BITS;
const TIMESTAMP_LEFT_SHIFT: i64 = SEQUENCE_BITS + WORKER_ID_BITS + DATACENTER_ID_BITS;
const SEQUENCE_MASK: i64 = -1 ^ (-1 << SEQUENCE_BITS);
#[derive(Debug)]
pub struct IdWorker {
worker_id: i64,
datacenter_id: i64,
sequence: i64,
last_timestamp: i64,
start_offset_timestamp: i64,
}
impl IdWorker {
pub fn new(worker_id: i64, datacenter_id: i64, start_offset_timestamp: i64) -> Self {
if worker_id < 0 || worker_id > MAX_WORKER_ID {
panic!(
"IdWorker: worker_id check failed: {}, MAX: {}",
worker_id, MAX_WORKER_ID
);
}
if datacenter_id < 0 || datacenter_id > MAX_DATACENTER_ID {
panic!(
"IdWorker: datacenter_id check failed: {}, MAX: {}",
datacenter_id, MAX_DATACENTER_ID
);
}
IdWorker {
worker_id,
datacenter_id,
sequence: 0,
last_timestamp: 0,
start_offset_timestamp,
}
}
pub fn next_id(&mut self) -> i64 {
let mut timestamp = self.gen_time();
assert!(timestamp >= self.last_timestamp);
if timestamp == self.last_timestamp {
self.sequence = (self.sequence + 1) & SEQUENCE_MASK;
if self.sequence == 0 {
loop {
timestamp = self.gen_time();
if timestamp > self.last_timestamp {
break;
}
}
}
} else {
self.sequence = 0;
}
self.last_timestamp = timestamp;
(timestamp << TIMESTAMP_LEFT_SHIFT)
| (self.datacenter_id << DATACENTER_ID_SHIFT)
| (self.worker_id << WORKER_ID_SHIFT)
| self.sequence
}
pub fn get_location(id: i64) -> (i64, i64) {
let mut c_id = id;
c_id >>= SEQUENCE_BITS;
c_id = Self::slice(c_id, 64 - WORKER_ID_BITS - DATACENTER_ID_BITS);
let worker_id = c_id >> 5;
let dc_id = Self::slice(c_id, 64 - DATACENTER_ID_BITS);
(worker_id, dc_id)
}
fn slice(id: i64, offset: i64) -> i64 {
let c_id = id << offset - 1;
let d_id = if c_id < 0 {
c_id ^ (0 - std::i64::MAX - 1)
} else {
c_id
};
d_id >> offset - 1
}
fn gen_time(&self) -> i64 {
let duration = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
let time = (duration.as_secs() * 1000 + duration.subsec_nanos() as u64 / 1_000_000) as i64
- self.start_offset_timestamp;
if time < 0 {
panic!("IdWorker: can't get correct time. current: {}", time);
}
time as i64
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_works() {
let mut worker = IdWorker::new(31, 31, 1586497735375);
let (dc_id, worker_id) = IdWorker::get_location(worker.next_id());
assert_eq!(worker_id, 31);
assert_eq!(dc_id, 31);
}
}