fix time smearing

if two messages have the same time,
this results i all kinds of sorting failures,
esp. in non-delta-muas and on forwarding messages.
so, no two messages sent out from delta have the same timestamp.
normally, this is no problem, but when things are sent too fast,
eg. on forwarding, we lend us some time from the future.

however, all this did not work
because we forgot to write back the modified time,
this is fixed by this commit, as well as some cleanup.

src/context.rs

@@ -57,7 +57,7 @@ pub struct Context {
     pub os_name: Option<String>,
     pub cmdline_sel_chat_id: Arc<RwLock<u32>>,
     pub bob: Arc<RwLock<BobStatus>>,
-    pub last_smeared_timestamp: Arc<RwLock<i64>>,
+    pub last_smeared_timestamp: RwLock<i64>,
     pub running_state: Arc<RwLock<RunningState>>,
     /// Mutex to avoid generating the key for the user more than once.
     pub generating_key_mutex: Mutex<()>,
@@ -130,7 +130,7 @@ impl Context {
             smtp_state: Arc::new((Mutex::new(Default::default()), Condvar::new())),
             oauth2_critical: Arc::new(Mutex::new(())),
             bob: Arc::new(RwLock::new(Default::default())),
-            last_smeared_timestamp: Arc::new(RwLock::new(0)),
+            last_smeared_timestamp: RwLock::new(0),
             cmdline_sel_chat_id: Arc::new(RwLock::new(0)),
             sentbox_thread: Arc::new(RwLock::new(JobThread::new(
                 "SENTBOX",

src/dc_tools.rs

@@ -1,7 +1,7 @@
 //! Some tools and enhancements to the used libraries, there should be
 //! no references to Context and other "larger" entities here.
 
-use core::cmp::max;
+use core::cmp::{max, min};
 use std::borrow::Cow;
 use std::ffi::{CStr, CString};
 use std::path::{Path, PathBuf};
@@ -166,10 +166,12 @@ pub(crate) fn dc_gm2local_offset() -> i64 {
 }
 
 /* timesmearing */
+const MAX_SECONDS_TO_LEND_FROM_FUTURE: i64 = 5;
+
 pub(crate) fn dc_smeared_time(context: &Context) -> i64 {
     /* function returns a corrected time(NULL) */
     let mut now = time();
-    let ts = *context.last_smeared_timestamp.clone().read().unwrap();
+    let ts = *context.last_smeared_timestamp.read().unwrap();
     if ts >= now {
         now = ts + 1;
     }
@@ -181,28 +183,29 @@ pub(crate) fn dc_create_smeared_timestamp(context: &Context) -> i64 {
     let now = time();
     let mut ret = now;
 
-    let ts = *context.last_smeared_timestamp.clone().write().unwrap();
-    if ret <= ts {
-        ret = ts + 1;
-        if ret - now > 5 {
-            ret = now + 5
+    let mut last_smeared_timestamp = context.last_smeared_timestamp.write().unwrap();
+    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
 }
 
 pub(crate) fn dc_create_smeared_timestamps(context: &Context, count: usize) -> i64 {
     /* get a range to timestamps that can be used uniquely */
     let now = time();
-    let start = now + (if count < 5 { count } else { 5 }) as i64 - count as i64;
+    let count = count as i64;
+    let mut start = now + min(count, MAX_SECONDS_TO_LEND_FROM_FUTURE) - count;
 
-    let ts = *context.last_smeared_timestamp.clone().write().unwrap();
-    if ts + 1 > start {
-        ts + 1
-    } else {
-        start
-    }
+    let mut last_smeared_timestamp = context.last_smeared_timestamp.write().unwrap();
+    start = max(*last_smeared_timestamp + 1, start);
+
+    *last_smeared_timestamp = start + count - 1;
+    start
 }
 
 /* Message-ID tools */
@@ -1355,4 +1358,34 @@ mod tests {
         let listflags: u32 = DC_GCL_VERIFIED_ONLY.try_into().unwrap();
         assert!(listflags_has(listflags, DC_GCL_ADD_SELF) == false);
     }
+
+    #[test]
+    fn test_create_smeared_timestamp() {
+        let t = dummy_context();
+        assert_ne!(
+            dc_create_smeared_timestamp(&t.ctx),
+            dc_create_smeared_timestamp(&t.ctx)
+        );
+        assert!(
+            dc_create_smeared_timestamp(&t.ctx)
+                >= SystemTime::now()
+                    .duration_since(SystemTime::UNIX_EPOCH)
+                    .unwrap()
+                    .as_secs() as i64
+        );
+    }
+
+    #[test]
+    fn test_create_smeared_timestamps() {
+        let t = dummy_context();
+        let count = MAX_SECONDS_TO_LEND_FROM_FUTURE - 1;
+        let start = dc_create_smeared_timestamps(&t.ctx, count as usize);
+        let next = dc_smeared_time(&t.ctx);
+        assert!((start + count - 1) < next);
+
+        let count = MAX_SECONDS_TO_LEND_FROM_FUTURE + 30;
+        let start = dc_create_smeared_timestamps(&t.ctx, count as usize);
+        let next = dc_smeared_time(&t.ctx);
+        assert!((start + count - 1) < next);
+    }
 }