1 files changed, 76 insertions, 0 deletions
diff --git a/src/mail_uuid.rs b/src/mail_uuid.rs
new file mode 100644
index 0000000..d0d582f
--- /dev/null
+++ b/src/mail_uuid.rs
@@ -0,0 +1,76 @@
+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))
+    }
+}