From 390bad0ec451a571e119903054b581a9d9a00cbe Mon Sep 17 00:00:00 2001
From: Quentin Dufour <quentin@deuxfleurs.fr>
Date: Mon, 27 Jun 2022 16:56:20 +0200
Subject: Refactor files in a "mail" crate

---
 src/mail/mail_ident.rs | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 src/mail/mail_ident.rs

(limited to 'src/mail/mail_ident.rs')

diff --git a/src/mail/mail_ident.rs b/src/mail/mail_ident.rs
new file mode 100644
index 0000000..07e053a
--- /dev/null
+++ b/src/mail/mail_ident.rs
@@ -0,0 +1,95 @@
+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::time::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 Mailrage/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, Debug)]
+pub struct MailIdent(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) -> MailIdent {
+        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));
+        MailIdent(res)
+    }
+}
+
+lazy_static! {
+    static ref GENERATOR: IdentGenerator = IdentGenerator::new();
+}
+
+pub fn gen_ident() -> MailIdent {
+    GENERATOR.gen()
+}
+
+// -- serde --
+
+impl<'de> Deserialize<'de> for MailIdent {
+    fn deserialize<D>(d: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let v = String::deserialize(d)?;
+        MailIdent::from_str(&v).map_err(D::Error::custom)
+    }
+}
+
+impl Serialize for MailIdent {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(&self.to_string())
+    }
+}
+
+impl ToString for MailIdent {
+    fn to_string(&self) -> String {
+        hex::encode(self.0)
+    }
+}
+
+impl FromStr for MailIdent {
+    type Err = &'static str;
+
+    fn from_str(s: &str) -> Result<MailIdent, &'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(MailIdent(tmp))
+    }
+}
-- 
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