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use std::time::{Duration, SystemTime, SystemTimeError};
pub type WebeID = u64;
pub struct WebeIDFactory {
epoch: SystemTime,
last_duration_ms: u64,
node_id: u64,
sequence: u16,
}
#[derive(Debug)]
pub enum WebeIDError {
BadEpoch,
BadLastDuration,
SequenceOverflow,
SystemTimeError(SystemTimeError),
TimeRewind,
}
impl From<SystemTimeError> for WebeIDError {
fn from(err: SystemTimeError) -> WebeIDError {
WebeIDError::SystemTimeError(err)
}
}
impl WebeIDFactory {
pub fn new(epoch: SystemTime, node_id: u8) -> Result<WebeIDFactory, WebeIDError> {
SystemTime::now().duration_since(epoch + Duration::from_millis(std::u16::MAX as u64))?;
Ok(WebeIDFactory {
epoch: epoch,
last_duration_ms: 0,
node_id: (node_id as u64) << 16,
sequence: 0,
})
}
pub fn new_with_last_time(epoch: SystemTime, last_duration_ms: u64, node_id: u8) -> Result<WebeIDFactory, WebeIDError> {
let mut factory = WebeIDFactory::new(epoch, node_id)?;
if SystemTime::now().duration_since(epoch)?.as_millis() <= last_duration_ms as u128 {
return Err(WebeIDError::BadLastDuration);
}
factory.last_duration_ms = last_duration_ms;
return Ok(factory);
}
pub fn next(&mut self) -> Result<WebeID, WebeIDError> {
let cur_duration_ms = SystemTime::now().duration_since(self.epoch)?.as_millis() as u64;
if cur_duration_ms < self.last_duration_ms {return Err(WebeIDError::TimeRewind)}
if cur_duration_ms > self.last_duration_ms {self.sequence = 0}
self.last_duration_ms = cur_duration_ms;
let new_id = ((cur_duration_ms as u64) << 24) | (self.node_id) | (self.sequence as u64);
match self.sequence.checked_add(1) {
Some(new_sequence) => self.sequence = new_sequence,
None => return Err(WebeIDError::SequenceOverflow)
}
return Ok(new_id);
}
pub fn epoch(&self) -> SystemTime {
return self.epoch;
}
pub fn last_duration_ms(&self) -> u64 {
return self.last_duration_ms;
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let epoch = SystemTime::UNIX_EPOCH
.checked_add(Duration::from_millis(1546300800000))
.expect("failed to create custom epoch");
let mut factory = WebeIDFactory::new(epoch, 0u8).unwrap();
let id = factory.next().unwrap();
println!("New ID: {:x}", id);
}
}