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use std::sync::atomic::{AtomicU64, Ordering};
use lazy_static::lazy_static;
use rand::prelude::*;
use serde::{de::Error, Deserialize, Deserializer, Serialize, Serializer};
use crate::time::now_msec;
/// A Mail UUID is composed of two components:
/// - a process identifier, 128 bits, itself composed of:
/// - the timestamp of when the process started, 64 bits
/// - a 64-bit random number
/// - a sequence number, 64 bits
#[derive(Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Debug)]
pub struct MailUuid(pub [u8; 24]);
struct UuidGenerator {
pid: u128,
sn: AtomicU64,
}
impl UuidGenerator {
fn new() -> Self {
let time = now_msec() as u128;
let rand = thread_rng().gen::<u64>() as u128;
Self {
pid: (time << 64) | rand,
sn: AtomicU64::new(0),
}
}
fn gen(&self) -> MailUuid {
let sn = self.sn.fetch_add(1, Ordering::Relaxed);
let mut res = [0u8; 24];
res[0..16].copy_from_slice(&u128::to_be_bytes(self.pid));
res[16..24].copy_from_slice(&u64::to_be_bytes(sn));
MailUuid(res)
}
}
lazy_static! {
static ref GENERATOR: UuidGenerator = UuidGenerator::new();
}
pub fn gen_uuid() -> MailUuid {
GENERATOR.gen()
}
// -- serde --
impl<'de> Deserialize<'de> for MailUuid {
fn deserialize<D>(d: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
let v = String::deserialize(d)?;
let bytes = hex::decode(v).map_err(|_| D::Error::custom("invalid hex"))?;
if bytes.len() != 24 {
return Err(D::Error::custom("bad length"));
}
let mut tmp = [0u8; 24];
tmp[..].copy_from_slice(&bytes);
Ok(Self(tmp))
}
}
impl Serialize for MailUuid {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
serializer.serialize_str(&hex::encode(self.0))
}
}
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