Lua listen_events(), await_event() => get_event_{pumps,next}().

Don't set up a Lua callback to receive incoming events, a la listen_events().
Don't listen on an arbitrary event pump, a la await_event().

Instead, the new get_event_pumps() entry point simply delivers the reply pump
and command pump names (as listen_events() did) without storing a Lua
callback.

Make LuaListener capture incoming events on the reply pump in a queue. This
avoids the problem of multiple events arriving too quickly for the Lua script
to retrieve. If the queue gets too big, discard the excess instead of blocking
the caller of post().

Then the new get_event_next() entry point retrieves the next (pump, data) pair
from the queue, blocking the Lua script until a suitable event arrives. This
is closer to the use of stdin for a LEAP plugin. It also addresses the
question: what should the Lua script's C++ coroutine do while waiting for an
incoming reply pump event?

Recast llluamanager_test.cpp for this new, more straightforward API.

Move LLLeap's and LuaListener's reply LLEventPump into LLLeapListener, which
they both use. This simplifies LLLeapListener's API, which was a little
convoluted: the caller supplied a connect callback to allow LLLeapListener to
connect some listener to the caller's reply pump. Now, instead, the caller
simply passes a bool(pumpname, data) callback to receive events incoming on
LLLeapListener's own reply pump.

Fix a latent bug in LLLeapListener: if a plugin called listen() more than once
with the same listener name, the new connection would not have been saved.

While at it, replace some older Boost features in LLLeapListener and LLLeap.

1 files changed, 31 insertions, 7 deletions

diff --git a/indra/llcommon/llleaplistener.cpp b/indra/llcommon/llleaplistener.cpp
index 471f52e91c..3dec5e6215 100644
--- a/indra/llcommon/llleaplistener.cpp
+++ b/indra/llcommon/llleaplistener.cpp
@@ -16,6 +16,7 @@
 // STL headers
 #include <algorithm>                // std::find_if
 #include <functional>
+#include <iomanip>                  // std::quoted
 #include <map>
 #include <set>
 // std headers
@@ -54,12 +55,19 @@
     return features;
 }
 
-LLLeapListener::LLLeapListener(const ConnectFunc& connect):
+LLLeapListener::LLLeapListener(const std::string_view& caller, const Callback& callback):
     // Each LEAP plugin has an instance of this listener. Make the command
     // pump name difficult for other such plugins to guess.
     LLEventAPI(LLUUID::generateNewID().asString(),
                "Operations relating to the LLSD Event API Plugin (LEAP) protocol"),
-    mConnect(connect)
+    mCaller(caller),
+    mCallback(callback),
+    // Troubling thought: what if one plugin intentionally messes with
+    // another plugin? LLEventPump names are in a single global namespace.
+    // Try to make that more difficult by generating a UUID for the reply-
+    // pump name -- so it should NOT need tweaking for uniqueness.
+    mReplyPump(LLUUID::generateNewID().asString()),
+    mReplyConn(connect(mReplyPump, mCaller))
 {
     LLSD need_name(LLSDMap("name", LLSD()));
     add("newpump",
@@ -133,8 +141,7 @@ void LLLeapListener::newpump(const LLSD& request)
         reply["name"] = name;
 
         // Now listen on this new pump with our plugin listener
-        std::string myname("llleap");
-        saveListener(name, myname, mConnect(new_pump, myname));
+        saveListener(name, mCaller, connect(new_pump, mCaller));
     }
     catch (const LLEventPumps::BadType& error)
     {
@@ -170,7 +177,7 @@ void LLLeapListener::listen(const LLSD& request)
             {
                 // "dest" unspecified means to direct events on "source"
                 // to our plugin listener.
-                saveListener(source_name, listener_name, mConnect(source, listener_name));
+                saveListener(source_name, listener_name, connect(source, listener_name));
             }
             reply["status"] = true;
         }
@@ -292,10 +299,27 @@ void LLLeapListener::getFeature(const LLSD& request) const
     }
 }
 
+LLBoundListener LLLeapListener::connect(LLEventPump& pump, const std::string& listener)
+{
+    // Connect to source pump with an adapter that calls our callback with the
+    // pump name as well as the event data.
+    return pump.listen(
+        listener,
+        [callback=mCallback, pump=pump.getName()]
+        (const LLSD& data)
+        { return callback(pump, data); });
+}
+
 void LLLeapListener::saveListener(const std::string& pump_name,
                                   const std::string& listener_name,
                                   const LLBoundListener& listener)
 {
-    mListeners.insert(ListenersMap::value_type(ListenersMap::key_type(pump_name, listener_name),
-                                               listener));
+    // Don't use insert() or emplace() because, if this (pump_name,
+    // listener_name) pair is already in mListeners, we *want* to overwrite it.
+    auto& listener_entry{ mListeners[ListenersMap::key_type(pump_name, listener_name)] };
+    // If we already stored a connection for this pump and listener name,
+    // disconnect it before overwriting it. But if this entry was newly
+    // created, disconnect() will be a no-op.
+    listener_entry.disconnect();
+    listener_entry = listener;
 }