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use std::str::FromStr;
use std::sync::atomic::{AtomicU64, Ordering};
use lazy_static::lazy_static;
use rand::prelude::*;
use serde::{de::Error, Deserialize, Deserializer, Serialize, Serializer};
use crate::timestamp::now_msec;
/// An internal Mail Identifier 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
/// They are not part of the protocol but an internal representation
/// required by Aerogramme.
/// Their main property is to be unique without having to rely
/// on synchronization between IMAP processes.
#[derive(Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Hash)]
pub struct UniqueIdent(pub [u8; 24]);
struct IdentGenerator {
pid: u128,
sn: AtomicU64,
}
impl IdentGenerator {
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) -> UniqueIdent {
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));
UniqueIdent(res)
}
}
lazy_static! {
static ref GENERATOR: IdentGenerator = IdentGenerator::new();
}
pub fn gen_ident() -> UniqueIdent {
GENERATOR.gen()
}
// -- serde --
impl<'de> Deserialize<'de> for UniqueIdent {
fn deserialize<D>(d: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
let v = String::deserialize(d)?;
UniqueIdent::from_str(&v).map_err(D::Error::custom)
}
}
impl Serialize for UniqueIdent {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
serializer.serialize_str(&self.to_string())
}
}
impl std::fmt::Display for UniqueIdent {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{}", hex::encode(self.0))
}
}
impl std::fmt::Debug for UniqueIdent {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{}", hex::encode(self.0))
}
}
impl FromStr for UniqueIdent {
type Err = &'static str;
fn from_str(s: &str) -> Result<UniqueIdent, &'static str> {
let bytes = hex::decode(s).map_err(|_| "invalid hex")?;
if bytes.len() != 24 {
return Err("bad length");
}
let mut tmp = [0u8; 24];
tmp[..].copy_from_slice(&bytes);
Ok(UniqueIdent(tmp))
}
}
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