From f9373b4430e67cf95f66a736a745d5bad572dbd9 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Fri, 25 Jan 2019 15:28:12 +0100
Subject: [PATCH] base: new Allocator_avl::construct_metadata method

The new method allows for the construction of a meta-data object inside
the reserved space of the allocator's meta data. It thereby alleviates
the need to copy the meta data object (via the assignment operator) as
done by the traditional 'metadata' setter method. This, in turn, allows
one to use non-copyable objects (like objects with constant member
variables) as meta data.
---
 repos/base/include/base/allocator_avl.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/repos/base/include/base/allocator_avl.h b/repos/base/include/base/allocator_avl.h
index 51896f9638..bce9fead39 100644
--- a/repos/base/include/base/allocator_avl.h
+++ b/repos/base/include/base/allocator_avl.h
@@ -19,6 +19,7 @@
 #include <base/output.h>
 #include <util/avl_tree.h>
 #include <util/misc_math.h>
+#include <util/construct_at.h>
 
 namespace Genode {
 
@@ -353,11 +354,24 @@ class Genode::Allocator_avl_tpl : public Allocator_avl_base
 		 */
 		void metadata(void *addr, BMDT bmd) const
 		{
-			Block *b = static_cast<Block *>(_find_by_address((addr_t)addr));
+			Block * const b = static_cast<Block *>(_find_by_address((addr_t)addr));
 			if (b) *static_cast<BMDT *>(b) = bmd;
 			else throw Assign_metadata_failed();
 		}
 
+		/**
+		 * Construct meta-data object in place
+		 *
+		 * \param ARGS  arguments passed to the meta-data constuctor
+		 */
+		template <typename... ARGS>
+		void construct_metadata(void *addr, ARGS &&... args)
+		{
+			Block * const b = static_cast<Block *>(_find_by_address((addr_t)addr));
+			if (b) construct_at<BMDT>(static_cast<BMDT *>(b), args...);
+			else throw Assign_metadata_failed();
+		}
+
 		/**
 		 * Return meta data that was attached to block at specified address
 		 */