Make smeared timestamp creation non-async

Using atomic operations instead,
so create_smeared_timestamp() can be used in sync functions,
such as SQL transactions.

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 ### Changes
+- Make smeared timestamp generation non-async. #4075
 
 ### Fixes
 

src/chat.rs

@@ -276,7 +276,7 @@ impl ChatId {
                     grpname,
                     grpid,
                     create_blocked,
-                    create_smeared_timestamp(context).await,
+                    create_smeared_timestamp(context),
                     create_protected,
                     param.unwrap_or_default(),
                 ],
@@ -482,7 +482,7 @@ impl ChatId {
                 self,
                 &msg_text,
                 cmd,
-                create_smeared_timestamp(context).await,
+                create_smeared_timestamp(context),
                 None,
                 None,
                 None,
@@ -1956,7 +1956,6 @@ impl ChatIdBlocked {
             _ => (),
         }
 
-        let created_timestamp = create_smeared_timestamp(context).await;
         let chat_id = context
             .sql
             .transaction(move |transaction| {
@@ -1969,7 +1968,7 @@ impl ChatIdBlocked {
                         chat_name,
                         params.to_string(),
                         create_blocked as u8,
-                        created_timestamp,
+                        create_smeared_timestamp(context)
                     ],
                 )?;
                 let chat_id = ChatId::new(
@@ -2117,7 +2116,7 @@ async fn prepare_msg_common(
             context,
             msg,
             update_msg_id,
-            create_smeared_timestamp(context).await,
+            create_smeared_timestamp(context),
         )
         .await?;
     msg.chat_id = chat_id;
@@ -2842,7 +2841,7 @@ pub async fn create_group_chat(
                 Chattype::Group,
                 chat_name,
                 grpid,
-                create_smeared_timestamp(context).await,
+                create_smeared_timestamp(context),
             ],
         )
         .await?;
@@ -2900,7 +2899,7 @@ pub async fn create_broadcast_list(context: &Context) -> Result<ChatId> {
                 Chattype::Broadcast,
                 chat_name,
                 grpid,
-                create_smeared_timestamp(context).await,
+                create_smeared_timestamp(context),
             ],
         )
         .await?;
@@ -3361,7 +3360,7 @@ pub async fn forward_msgs(context: &Context, msg_ids: &[MsgId], chat_id: ChatId)
         if let Some(reason) = chat.why_cant_send(context).await? {
             bail!("cannot send to {}: {}", chat_id, reason);
         }
-        curr_timestamp = create_smeared_timestamps(context, msg_ids.len()).await;
+        curr_timestamp = create_smeared_timestamps(context, msg_ids.len());
         let ids = context
             .sql
             .query_map(
@@ -3563,7 +3562,7 @@ pub async fn add_device_msg_with_importance(
         msg.try_calc_and_set_dimensions(context).await.ok();
         prepare_msg_blob(context, msg).await?;
 
-        let timestamp_sent = create_smeared_timestamp(context).await;
+        let timestamp_sent = create_smeared_timestamp(context);
 
         // makes sure, the added message is the last one,
         // even if the date is wrong (useful esp. when warning about bad dates)

src/context.rs

@@ -27,6 +27,7 @@ use crate::quota::QuotaInfo;
 use crate::scheduler::Scheduler;
 use crate::sql::Sql;
 use crate::stock_str::StockStrings;
+use crate::timesmearing::SmearedTimestamp;
 use crate::tools::{duration_to_str, time};
 
 /// Builder for the [`Context`].
@@ -189,7 +190,7 @@ pub struct InnerContext {
     /// Blob directory path
     pub(crate) blobdir: PathBuf,
     pub(crate) sql: Sql,
-    pub(crate) last_smeared_timestamp: RwLock<i64>,
+    pub(crate) smeared_timestamp: SmearedTimestamp,
     running_state: RwLock<RunningState>,
     /// Mutex to avoid generating the key for the user more than once.
     pub(crate) generating_key_mutex: Mutex<()>,
@@ -360,7 +361,7 @@ impl Context {
             blobdir,
             running_state: RwLock::new(Default::default()),
             sql: Sql::new(dbfile),
-            last_smeared_timestamp: RwLock::new(0),
+            smeared_timestamp: SmearedTimestamp::new(),
             generating_key_mutex: Mutex::new(()),
             oauth2_mutex: Mutex::new(()),
             wrong_pw_warning_mutex: Mutex::new(()),

src/ephemeral.rs

@@ -650,7 +650,7 @@ mod tests {
     use crate::download::DownloadState;
     use crate::receive_imf::receive_imf;
     use crate::test_utils::TestContext;
-    use crate::tools::MAX_SECONDS_TO_LEND_FROM_FUTURE;
+    use crate::timesmearing::MAX_SECONDS_TO_LEND_FROM_FUTURE;
     use crate::{
         chat::{self, create_group_chat, send_text_msg, Chat, ChatItem, ProtectionStatus},
         tools::IsNoneOrEmpty,

src/lib.rs

@@ -92,6 +92,7 @@ mod smtp;
 mod socks;
 pub mod stock_str;
 mod sync;
+mod timesmearing;
 mod token;
 mod update_helper;
 pub mod webxdc;

src/message.rs

@@ -1771,13 +1771,8 @@ async fn ndn_maybe_add_info_msg(
                 // Tell the user which of the recipients failed if we know that (because in
                 // a group, this might otherwise be unclear)
                 let text = stock_str::failed_sending_to(context, contact.get_display_name()).await;
-                chat::add_info_msg(
-                    context,
-                    chat_id,
-                    &text,
-                    create_smeared_timestamp(context).await,
-                )
-                .await?;
+                chat::add_info_msg(context, chat_id, &text, create_smeared_timestamp(context))
+                    .await?;
                 context.emit_event(EventType::ChatModified(chat_id));
             }
         }

src/mimefactory.rs

@@ -250,7 +250,7 @@ impl<'a> MimeFactory<'a> {
             .get_config(Config::Selfstatus)
             .await?
             .unwrap_or_default();
-        let timestamp = create_smeared_timestamp(context).await;
+        let timestamp = create_smeared_timestamp(context);
 
         let res = MimeFactory::<'a> {
             from_addr,

src/receive_imf.rs

@@ -203,7 +203,7 @@ pub(crate) async fn receive_imf_inner(
     )
     .await?;
 
-    let rcvd_timestamp = smeared_time(context).await;
+    let rcvd_timestamp = smeared_time(context);
 
     // Sender timestamp is allowed to be a bit in the future due to
     // unsynchronized clocks, but not too much.
@@ -1380,7 +1380,7 @@ async fn calc_sort_timestamp(
         }
     }
 
-    Ok(min(sort_timestamp, smeared_time(context).await))
+    Ok(min(sort_timestamp, smeared_time(context)))
 }
 
 async fn lookup_chat_by_reply(

src/timesmearing.rs

@@ -0,0 +1,193 @@
+//! # Time smearing.
+//!
+//! As e-mails typically only use a second-based-resolution for timestamps,
+//! the order of two mails sent withing one second is unclear.
+//! This is bad e.g. when forwarding some messages from a chat -
+//! these messages will appear at the recipient easily out of order.
+//!
+//! We work around this issue by not sending out two mails with the same timestamp.
+//! For this purpose, in short, we track the last timestamp used in `last_smeared_timestamp`
+//! when another timestamp is needed in the same second, we use `last_smeared_timestamp+1`
+//! after some moments without messages sent out,
+//! `last_smeared_timestamp` is again in sync with the normal time.
+//!
+//! However, we do not do all this for the far future,
+//! but at max `MAX_SECONDS_TO_LEND_FROM_FUTURE`
+
+use std::cmp::{max, min};
+use std::sync::atomic::{AtomicI64, Ordering};
+
+pub(crate) const MAX_SECONDS_TO_LEND_FROM_FUTURE: i64 = 5;
+
+/// Smeared timestamp generator.
+#[derive(Debug)]
+pub struct SmearedTimestamp {
+    /// Next timestamp available for allocation.
+    smeared_timestamp: AtomicI64,
+}
+
+impl SmearedTimestamp {
+    /// Creates a new smeared timestamp generator.
+    pub fn new() -> Self {
+        Self {
+            smeared_timestamp: AtomicI64::new(0),
+        }
+    }
+
+    /// Allocates `count` unique timestamps.
+    ///
+    /// Returns the first allocated timestamp.
+    pub fn create_n(&self, now: i64, count: i64) -> i64 {
+        let mut prev = self.smeared_timestamp.load(Ordering::Relaxed);
+        loop {
+            // Advance the timestamp if it is in the past,
+            // but keep `count - 1` timestamps from the past if possible.
+            let t = max(prev, now - count + 1);
+
+            // Rewind the time back if there is no room
+            // to allocate `count` timestamps without going too far into the future.
+            // Not going too far into the future
+            // is more important than generating unique timestamps.
+            let first = min(t, now + MAX_SECONDS_TO_LEND_FROM_FUTURE - count + 1);
+
+            // Allocate `count` timestamps by advancing the current timestamp.
+            let next = first + count;
+
+            if let Err(x) = self.smeared_timestamp.compare_exchange_weak(
+                prev,
+                next,
+                Ordering::Relaxed,
+                Ordering::Relaxed,
+            ) {
+                prev = x;
+            } else {
+                return first;
+            }
+        }
+    }
+
+    /// Creates a single timestamp.
+    pub fn create(&self, now: i64) -> i64 {
+        self.create_n(now, 1)
+    }
+
+    /// Returns the current smeared timestamp.
+    pub fn current(&self) -> i64 {
+        self.smeared_timestamp.load(Ordering::Relaxed)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::time::SystemTime;
+
+    use super::*;
+    use crate::test_utils::TestContext;
+    use crate::tools::{create_smeared_timestamp, create_smeared_timestamps, smeared_time, time};
+
+    #[test]
+    fn test_smeared_timestamp() {
+        let smeared_timestamp = SmearedTimestamp::new();
+        let now = time();
+
+        assert_eq!(smeared_timestamp.current(), 0);
+
+        for i in 0..MAX_SECONDS_TO_LEND_FROM_FUTURE {
+            assert_eq!(smeared_timestamp.create(now), now + i);
+        }
+        assert_eq!(
+            smeared_timestamp.create(now),
+            now + MAX_SECONDS_TO_LEND_FROM_FUTURE
+        );
+        assert_eq!(
+            smeared_timestamp.create(now),
+            now + MAX_SECONDS_TO_LEND_FROM_FUTURE
+        );
+
+        // System time rewinds back by 1000 seconds.
+        let now = now - 1000;
+        assert_eq!(
+            smeared_timestamp.create(now),
+            now + MAX_SECONDS_TO_LEND_FROM_FUTURE
+        );
+        assert_eq!(
+            smeared_timestamp.create(now),
+            now + MAX_SECONDS_TO_LEND_FROM_FUTURE
+        );
+        assert_eq!(
+            smeared_timestamp.create(now + 1),
+            now + MAX_SECONDS_TO_LEND_FROM_FUTURE + 1
+        );
+        assert_eq!(smeared_timestamp.create(now + 100), now + 100);
+        assert_eq!(smeared_timestamp.create(now + 100), now + 101);
+        assert_eq!(smeared_timestamp.create(now + 100), now + 102);
+    }
+
+    #[test]
+    fn test_create_n_smeared_timestamps() {
+        let smeared_timestamp = SmearedTimestamp::new();
+        let now = time();
+
+        // Create a single timestamp to initialize the generator.
+        assert_eq!(smeared_timestamp.create(now), now);
+
+        // Wait a minute.
+        let now = now + 60;
+
+        // Simulate forwarding 7 messages.
+        let forwarded_messages = 7;
+
+        // We have not sent anything for a minute,
+        // so we can take the current timestamp and take 6 timestamps from the past.
+        assert_eq!(smeared_timestamp.create_n(now, forwarded_messages), now - 6);
+
+        assert_eq!(smeared_timestamp.current(), now + 1);
+
+        // Wait 4 seconds.
+        // Now we have 3 free timestamps in the past.
+        let now = now + 4;
+
+        assert_eq!(smeared_timestamp.current(), now - 3);
+
+        // Forward another 7 messages.
+        // We can only lend 3 timestamps from the past.
+        assert_eq!(smeared_timestamp.create_n(now, forwarded_messages), now - 3);
+
+        // We had to borrow 3 timestamps from the future
+        // because there were not enough timestamps in the past.
+        assert_eq!(smeared_timestamp.current(), now + 4);
+
+        // Forward another 7 messages.
+        // We cannot use more than 5 timestamps from the future,
+        // so we use 5 timestamps from the future,
+        // the current timestamp and one timestamp from the past.
+        assert_eq!(smeared_timestamp.create_n(now, forwarded_messages), now - 1);
+    }
+
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_create_smeared_timestamp() {
+        let t = TestContext::new().await;
+        assert_ne!(create_smeared_timestamp(&t), create_smeared_timestamp(&t));
+        assert!(
+            create_smeared_timestamp(&t)
+                >= SystemTime::now()
+                    .duration_since(SystemTime::UNIX_EPOCH)
+                    .unwrap()
+                    .as_secs() as i64
+        );
+    }
+
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_create_smeared_timestamps() {
+        let t = TestContext::new().await;
+        let count = MAX_SECONDS_TO_LEND_FROM_FUTURE - 1;
+        let start = create_smeared_timestamps(&t, count as usize);
+        let next = smeared_time(&t);
+        assert!((start + count - 1) < next);
+
+        let count = MAX_SECONDS_TO_LEND_FROM_FUTURE + 30;
+        let start = create_smeared_timestamps(&t, count as usize);
+        let next = smeared_time(&t);
+        assert!((start + count - 1) < next);
+    }
+}

src/tools.rs

@@ -3,7 +3,6 @@
 
 #![allow(missing_docs)]
 
-use core::cmp::{max, min};
 use std::borrow::Cow;
 use std::fmt;
 use std::io::Cursor;
@@ -140,63 +139,27 @@ pub(crate) fn gm2local_offset() -> i64 {
     i64::from(lt.offset().local_minus_utc())
 }
 
-// timesmearing
-// - as e-mails typically only use a second-based-resolution for timestamps,
-//   the order of two mails sent withing one second is unclear.
-//   this is bad eg. when forwarding some messages from a chat -
-//   these messages will appear at the recipient easily out of order.
-// - we work around this issue by not sending out two mails with the same timestamp.
-// - for this purpose, in short, we track the last timestamp used in `last_smeared_timestamp`
-//   when another timestamp is needed in the same second, we use `last_smeared_timestamp+1`
-// - after some moments without messages sent out,
-//   `last_smeared_timestamp` is again in sync with the normal time.
-// - however, we do not do all this for the far future,
-//   but at max `MAX_SECONDS_TO_LEND_FROM_FUTURE`
-pub(crate) const MAX_SECONDS_TO_LEND_FROM_FUTURE: i64 = 5;
-
 /// Returns the current smeared timestamp,
 ///
 /// The returned timestamp MUST NOT be sent out.
-pub(crate) async fn smeared_time(context: &Context) -> i64 {
-    let mut now = time();
-    let ts = *context.last_smeared_timestamp.read().await;
-    if ts >= now {
-        now = ts + 1;
-    }
-
-    now
+pub(crate) fn smeared_time(context: &Context) -> i64 {
+    let now = time();
+    let ts = context.smeared_timestamp.current();
+    std::cmp::max(ts, now)
 }
 
 /// Returns a timestamp that is guaranteed to be unique.
-pub(crate) async fn create_smeared_timestamp(context: &Context) -> i64 {
+pub(crate) fn create_smeared_timestamp(context: &Context) -> i64 {
     let now = time();
-    let mut ret = now;
-
-    let mut last_smeared_timestamp = context.last_smeared_timestamp.write().await;
-    if ret <= *last_smeared_timestamp {
-        ret = *last_smeared_timestamp + 1;
-        if ret - now > MAX_SECONDS_TO_LEND_FROM_FUTURE {
-            ret = now + MAX_SECONDS_TO_LEND_FROM_FUTURE
-        }
-    }
-
-    *last_smeared_timestamp = ret;
-    ret
+    context.smeared_timestamp.create(now)
 }
 
 // creates `count` timestamps that are guaranteed to be unique.
-// the frist created timestamps is returned directly,
+// the first created timestamps is returned directly,
 // get the other timestamps just by adding 1..count-1
-pub(crate) async fn create_smeared_timestamps(context: &Context, count: usize) -> i64 {
+pub(crate) fn create_smeared_timestamps(context: &Context, count: usize) -> i64 {
     let now = time();
-    let count = count as i64;
-    let mut start = now + min(count, MAX_SECONDS_TO_LEND_FROM_FUTURE) - count;
-
-    let mut last_smeared_timestamp = context.last_smeared_timestamp.write().await;
-    start = max(*last_smeared_timestamp + 1, start);
-
-    *last_smeared_timestamp = start + count - 1;
-    start
+    context.smeared_timestamp.create_n(now, count as i64)
 }
 
 // if the system time is not plausible, once a day, add a device message.
@@ -1071,36 +1034,6 @@ DKIM Results: Passed=true, Works=true, Allow_Keychange=true";
         assert!(!file_exist!(context, &fn0));
     }
 
-    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-    async fn test_create_smeared_timestamp() {
-        let t = TestContext::new().await;
-        assert_ne!(
-            create_smeared_timestamp(&t).await,
-            create_smeared_timestamp(&t).await
-        );
-        assert!(
-            create_smeared_timestamp(&t).await
-                >= SystemTime::now()
-                    .duration_since(SystemTime::UNIX_EPOCH)
-                    .unwrap()
-                    .as_secs() as i64
-        );
-    }
-
-    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-    async fn test_create_smeared_timestamps() {
-        let t = TestContext::new().await;
-        let count = MAX_SECONDS_TO_LEND_FROM_FUTURE - 1;
-        let start = create_smeared_timestamps(&t, count as usize).await;
-        let next = smeared_time(&t).await;
-        assert!((start + count - 1) < next);
-
-        let count = MAX_SECONDS_TO_LEND_FROM_FUTURE + 30;
-        let start = create_smeared_timestamps(&t, count as usize).await;
-        let next = smeared_time(&t).await;
-        assert!((start + count - 1) < next);
-    }
-
     #[test]
     fn test_duration_to_str() {
         assert_eq!(duration_to_str(Duration::from_secs(0)), "0h 0m 0s");

src/webxdc.rs

@@ -408,7 +408,7 @@ impl Context {
             .create_status_update_record(
                 &mut instance,
                 update_str,
-                create_smeared_timestamp(self).await,
+                create_smeared_timestamp(self),
                 send_now,
                 ContactId::SELF,
             )