From dc8fc1a33c3a74de7fbf42a1ad062e7588582f95 Mon Sep 17 00:00:00 2001
From: Christian Prochaska <christian.prochaska@genode-labs.com>
Date: Tue, 8 Oct 2013 19:09:30 +0200
Subject: [PATCH] Ring_buffer: add 'avail_capacity()' function

The 'avail_capacity()' function returns how many more elements would
currently fit into the ring buffer.

Fixes #921.
---
 os/include/os/ring_buffer.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/os/include/os/ring_buffer.h b/os/include/os/ring_buffer.h
index 392ef31fd0..60a9b99ad4 100644
--- a/os/include/os/ring_buffer.h
+++ b/os/include/os/ring_buffer.h
@@ -89,7 +89,18 @@ class Ring_buffer
 		/**
 		 * Return true if ring buffer is empty
 		 */
-		bool empty() { return _tail == _head; }
+		bool empty() const { return _tail == _head; }
+
+		/**
+		 * Return the remaining capacity
+		 */
+		int avail_capacity() const
+		{
+			if (_head >= _tail)
+				return QUEUE_SIZE - _head + _tail - 1;
+			else
+				return _tail - _head - 1;
+		}
 };
 
 #endif /* _INCLUDE__OS__RING_BUFFER_H_ */