From d04ce4cb7d4aa3eb72bc79c09dfe5bb025ad79f4 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sat, 17 Nov 2012 21:50:35 +0000
Subject: Gracefully handle failure to send notifications due to buffer
 overrun.

git-svn-id: http://svn.drobilla.net/lad/trunk/ingen@4827 a436a847-0d15-0410-975c-d299462d15a1
---
 src/server/Context.cpp  | 16 +++++++++-------
 src/server/Context.hpp  |  6 ++++--
 src/server/PortImpl.cpp | 10 +++++++---
 3 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/src/server/Context.cpp b/src/server/Context.cpp
index 3b07373d..20d78c0e 100644
--- a/src/server/Context.cpp
+++ b/src/server/Context.cpp
@@ -53,7 +53,7 @@ Context::Context(Engine& engine, ID id)
 	, _realtime(true)
 {}
 
-void
+bool
 Context::notify(LV2_URID           key,
                 FrameTime          time,
                 PortImpl*          port,
@@ -63,14 +63,16 @@ Context::notify(LV2_URID           key,
 {
 	const Notification n(port, time, key, size, type);
 	if (_event_sink.write_space() < sizeof(n) + size) {
-		_engine.log().warn("Notification ring overflow\n");
+		return false;
+	}
+	if (_event_sink.write(sizeof(n), &n) != sizeof(n)) {
+		_engine.log().error("Error writing header to notification ring\n");
+	} else if (_event_sink.write(size, body) != size) {
+		_engine.log().error("Error writing body to notification ring\n");
 	} else {
-		if (_event_sink.write(sizeof(n), &n) != sizeof(n)) {
-			_engine.log().error("Error writing header to notification ring\n");
-		} else if (_event_sink.write(size, body) != size) {
-			_engine.log().error("Error writing body to notification ring\n");
-		}
+		return true;
 	}
+	return false;
 }
 
 void
diff --git a/src/server/Context.hpp b/src/server/Context.hpp
index cabfcc89..5343b817 100644
--- a/src/server/Context.hpp
+++ b/src/server/Context.hpp
@@ -53,8 +53,10 @@ public:
 
 	virtual ~Context() {}
 
-	/** Send a notification from this run context. */
-	void notify(LV2_URID           key  = 0,
+	/** Send a notification from this run context.
+	 * @return false on failure (ring is full)
+	 */
+	bool notify(LV2_URID           key  = 0,
 	            FrameTime          time = 0,
 	            PortImpl*          port = 0,
 	            uint32_t           size = 0,
diff --git a/src/server/PortImpl.cpp b/src/server/PortImpl.cpp
index a5fe8fe6..dfd24dc0 100644
--- a/src/server/PortImpl.cpp
+++ b/src/server/PortImpl.cpp
@@ -367,9 +367,13 @@ PortImpl::broadcast_value(Context& context, bool force)
 	}
 
 	if (val.is_valid() && (force || val != _last_broadcasted_value)) {
-		_last_broadcasted_value = val;
-		context.notify(key, context.start(), this,
-		               val.size(), val.type(), val.get_body());
+		if (context.notify(key, context.start(), this,
+		                   val.size(), val.type(), val.get_body())) {
+			_last_broadcasted_value = val;
+		}
+		
+		/* On failure, last_broadcasted_value remains unaffected, so we'll try
+		   again next cycle and so on until the value is finally delivered. */
 	}
 }
 
-- 
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