4 files changed, 80 insertions, 19 deletions

diff --git a/indra/llcommon/llcallbacklist.cpp b/indra/llcommon/llcallbacklist.cpp
index 7f7fdc7370..85c73fec8f 100644
--- a/indra/llcommon/llcallbacklist.cpp
+++ b/indra/llcommon/llcallbacklist.cpp
@@ -130,22 +130,40 @@ LLCallbackList::handle_t LLCallbackList::doOnIdleRepeating( const bool_func_t& f
 *****************************************************************************/
 LLLater::LLLater() {}
 
-// Call a given callable once at specified timestamp.
-LLLater::handle_t LLLater::doAtTime(nullary_func_t callable, LLDate::timestamp time)
+LLLater::DoneMap::iterator LLLater::doAtTime1(LLDate::timestamp time)
 {
-    bool first{ mQueue.empty() };
     // Pick token FIRST to store a self-reference in mQueue's managed node as
     // well as in mHandles. Pre-increment to distinguish 0 from any live
     // handle_t.
     token_t token{ ++mToken };
-    auto handle{ mQueue.emplace(callable, time, token) };
-    mHandles.emplace(token, handle);
+    auto [iter, inserted]{ mDoneTimes.emplace(token, time) };
+    llassert(inserted);
+    return iter;
+}
+
+LLLater::handle_t LLLater::doAtTime2(nullary_func_t callable, DoneMap::iterator iter)
+{
+    bool first{ mQueue.empty() };
+    // DoneMap::iterator references (token, time) pair
+    auto handle{ mQueue.emplace(callable, iter->first, iter->second) };
+    auto hiter{ mHandles.emplace(iter->first, handle).first };
+    // When called by Periodic, we're passed an existing DoneMap entry,
+    // meaning the token already exists, meaning emplace() will tell us it
+    // found an existing entry rather than creating a new one. In that case,
+    // it's essential to update the handle.
+    hiter->second = handle;
     if (first)
     {
         // If this is our first entry, register for regular callbacks.
         mLive = LLCallbackList::instance().doOnIdleRepeating([this]{ return tick(); });
     }
-    return handle_t{ token };
+    return { iter->first };
+}
+
+// Call a given callable once at specified timestamp.
+LLLater::handle_t LLLater::doAtTime(nullary_func_t callable, LLDate::timestamp time)
+{
+    return doAtTime2(callable, doAtTime1(time));
 }
 
 // Call a given callable once after specified interval.
@@ -160,11 +178,11 @@ LLLater::handle_t LLLater::doAfterInterval(nullary_func_t callable, F32 seconds)
 
 // For doPeriodically(), we need a struct rather than a lambda because a
 // struct, unlike a lambda, has access to 'this'.
-struct Periodic
+struct LLLater::Periodic
 {
     LLLater* mLater;
+    DoneMap::iterator mDone;
     bool_func_t mCallable;
-    LLDate::timestamp mNext;
     F32 mSeconds;
 
     void operator()()
@@ -175,8 +193,9 @@ struct Periodic
             // Don't call doAfterInterval(), which rereads LLDate::now(),
             // since that would defer by however long it took us to wake
             // up and notice plus however long callable() took to run.
-            mNext += mSeconds;
-            mLater->doAtTime(*this, mNext);
+            // Bump our mDoneTimes entry so getRemaining() can track.
+            mDone->second += mSeconds;
+            mLater->doAtTime2(*this, mDone);
         }
     }
 };
@@ -186,17 +205,32 @@ LLLater::handle_t LLLater::doPeriodically(bool_func_t callable, F32 seconds)
 {
     // Passing seconds <= 0 will produce an infinite loop.
     llassert(seconds > 0);
-    auto next{ LLDate::now().secondsSinceEpoch() + seconds };
-    return doAtTime(Periodic{ this, callable, next, seconds }, next);
+    auto iter{ doAtTime1(LLDate::now().secondsSinceEpoch() + seconds) };
+    // The whole reason we split doAtTime() into doAtTime1() and doAtTime2()
+    // is to be able to bind the mDoneTimes entry into Periodic.
+    return doAtTime2(Periodic{ this, iter, callable, seconds }, iter);
 }
 
-bool LLLater::isRunning(handle_t timer)
+bool LLLater::isRunning(handle_t timer) const
 {
     // A default-constructed timer isn't running.
     // A timer we don't find in mHandles has fired or been canceled.
     return timer && mHandles.find(timer.token) != mHandles.end();
 }
 
+F32 LLLater::getRemaining(handle_t timer) const
+{
+    auto found{ mDoneTimes.find(timer.token) };
+    if (found == mDoneTimes.end())
+    {
+        return 0.f;
+    }
+    else
+    {
+        return found->second - LLDate::now().secondsSinceEpoch();
+    }
+}
+
 // Cancel a future timer set by doAtTime(), doAfterInterval(), doPeriodically()
 bool LLLater::cancel(handle_t& timer)
 {
@@ -240,6 +274,8 @@ bool LLLater::cancel(const handle_t& timer)
     mQueue.erase(found->second);
     // before erasing timer.token from mHandles
     mHandles.erase(found);
+    // don't forget to erase mDoneTimes entry
+    mDoneTimes.erase(timer.token);
     if (mQueue.empty())
     {
         // If that was the last active timer, unregister for callbacks.
@@ -282,6 +318,8 @@ bool LLLater::tick()
         auto current{ top };
         // remove the mHandles entry referencing this task
         mHandles.erase(current.mToken);
+        // and the mDoneTimes entry
+        mDoneTimes.erase(current.mToken);
         // before removing the mQueue task entry itself
         mQueue.pop();
         // okay, NOW run 
diff --git a/indra/llcommon/llcallbacklist.h b/indra/llcommon/llcallbacklist.h
index 522a9b838b..17adb7f431 100644
--- a/indra/llcommon/llcallbacklist.h
+++ b/indra/llcommon/llcallbacklist.h
@@ -114,13 +114,13 @@ class LLLater: public LLSingleton<LLLater>
     struct func_at
     {
         nullary_func_t mFunc;
-        LLDate::timestamp mTime;
         token_t mToken;
+        LLDate::timestamp mTime;
 
-        func_at(const nullary_func_t& func, LLDate::timestamp tm, token_t token):
+        func_at(const nullary_func_t& func, token_t token, LLDate::timestamp tm):
             mFunc(func),
-            mTime(tm),
-            mToken(token)
+            mToken(token),
+            mTime(tm)
         {}
 
         friend bool operator<(const func_at& lhs, const func_at& rhs)
@@ -165,7 +165,9 @@ public:
     handle_t doPeriodically(bool_func_t callable, F32 seconds);
 
     // test whether specified handle is still live
-    bool isRunning(handle_t timer);
+    bool isRunning(handle_t timer) const;
+    // check remaining time
+    F32 getRemaining(handle_t timer) const;
 
     // Cancel a future timer set by doAtTime(), doAfterInterval(), doPeriodically().
     // Return true iff the handle corresponds to a live timer.
@@ -239,10 +241,19 @@ private:
     // the heap aka priority queue
     queue_t mQueue;
     // handles we've returned that haven't yet canceled
-    std::unordered_map<token_t, queue_t::handle_type> mHandles;
+    using HandleMap = std::unordered_map<token_t, queue_t::handle_type>;
+    HandleMap mHandles;
+    using DoneMap = std::unordered_map<token_t, LLDate::timestamp>;
+    DoneMap mDoneTimes;
     token_t mToken{ 0 };
     // While mQueue is non-empty, register for regular callbacks.
     LLCallbackList::temp_handle_t mLive;
+
+    struct Periodic;
+
+    // internal implementation for doAtTime()
+    DoneMap::iterator doAtTime1(LLDate::timestamp time);
+    handle_t doAtTime2(nullary_func_t callable, DoneMap::iterator iter);
 };
 
 /*-------------------- legacy names in global namespace --------------------*/
diff --git a/indra/llcommon/lleventtimer.cpp b/indra/llcommon/lleventtimer.cpp
index b163ad375c..0f8d1e636f 100644
--- a/indra/llcommon/lleventtimer.cpp
+++ b/indra/llcommon/lleventtimer.cpp
@@ -56,3 +56,13 @@ void LLEventTimer::stop()
 {
     LLLater::instance().cancel(mTimer);
 }
+
+bool LLEventTimer::isRunning()
+{
+    return LLLater::instance().isRunning(mTimer);
+}
+
+F32 LLEventTimer::getRemaining()
+{
+    return LLLater::instance().getRemaining(mTimer);
+}
diff --git a/indra/llcommon/lleventtimer.h b/indra/llcommon/lleventtimer.h
index 34ff157e22..05d8bc038d 100644
--- a/indra/llcommon/lleventtimer.h
+++ b/indra/llcommon/lleventtimer.h
@@ -42,6 +42,8 @@ public:
 
 	void start();
 	void stop();
+	bool isRunning();
+	F32 getRemaining();
 
 	//function to be called at the supplied frequency
 	// Normally return false; true will delete the timer after the function returns.