From 8bb8d7e5b7433ada8eef068016054d4eb2c645b8 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Thu, 30 May 2019 16:28:45 -0400
Subject: [PATCH] SL-11216: Introduce generic LLStoreListener<T> to capture
event data.
LLStoreListener is an adapter initialized with a reference to an LLEventPump
on which to listen, a reference to a variable into which to store received
data, and an optional llsd::drill() path to extract desired data from each
event received on the subject LLEventPump.
In effect, LLStoreListener is like a miniature LLEventAPI whose only operation
is to store to its destination variable.
---
indra/llcommon/lleventfilter.h | 51 ++++++++++++++++++++++++++++++++++
1 file changed, 51 insertions(+)
diff --git a/indra/llcommon/lleventfilter.h b/indra/llcommon/lleventfilter.h
index ff8fc9bc7fc..8e7c0755815 100644
--- a/indra/llcommon/lleventfilter.h
+++ b/indra/llcommon/lleventfilter.h
@@ -32,6 +32,7 @@
#include "llevents.h"
#include "stdtypes.h"
#include "lltimer.h"
+#include "llsdutil.h"
#include <boost/function.hpp>
/**
@@ -376,4 +377,54 @@ class LLEventBatchThrottle: public LLEventThrottle
std::size_t mBatchSize;
};
+/**
+ * LLStoreListener self-registers on the LLEventPump of interest, and
+ * unregisters on destruction. As long as it exists, a particular element is
+ * extracted from every event that comes through the upstream LLEventPump and
+ * stored into the target variable.
+ *
+ * This is implemented as a subclass of LLEventFilter, though strictly
+ * speaking it isn't really a "filter" at all: it never passes incoming events
+ * to its own listeners, if any.
+ *
+ * TBD: A variant based on output iterators that stores and then increments
+ * the iterator. Useful with boost::coroutine2!
+ */
+template <typename T>
+class LLStoreListener: public LLEventFilter
+{
+public:
+ // pass target and optional path to element
+ LLStoreListener(T& target, const LLSD& path=LLSD(), bool consume=false):
+ LLEventFilter("store"),
+ mTarget(target),
+ mPath(path),
+ mConsume(consume)
+ {}
+ // construct and connect
+ LLStoreListener(LLEventPump& source, T& target, const LLSD& path=LLSD(), bool consume=false):
+ LLEventFilter(source, "store"),
+ mTarget(target),
+ mPath(path),
+ mConsume(consume)
+ {}
+
+ // Calling post() with an LLSD event extracts the element indicated by
+ // path, then stores it to mTarget.
+ virtual bool post(const LLSD& event)
+ {
+ // Extract the element specified by 'mPath' from 'event'. To perform a
+ // generic type-appropriate store through mTarget, construct an
+ // LLSDParam<T> and store that, thus engaging LLSDParam's custom
+ // conversions.
+ mTarget = LLSDParam<T>(llsd::drill(event, mPath));
+ return mConsume;
+ }
+
+private:
+ T& mTarget;
+ const LLSD mPath;
+ const bool mConsume;
+};
+
#endif /* ! defined(LL_LLEVENTFILTER_H) */
--
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