base: Add const qualifiers to 'util/list.h'

This patch adds support for iterating through a const list. This allows
users of lists to be more rigid with regard to constness. Furthermore,
the patch adds the function 'List::insert_at' for inserting an element
at a specified position. By adding this function, we can remove code
duplication in nitpicker.

base/include/util/list.h

@@ -34,7 +34,7 @@ namespace Genode {
 
 					friend class List;
 
-					LT *_next;
+					LT mutable *_next;
 
 				public:
 
@@ -53,34 +53,44 @@ namespace Genode {
 			 *
 			 * Start with an empty list.
 			 */
-			List(): _first(0) { }
+			List() : _first(0) { }
 
 			/**
 			 * Return first list element
 			 */
-			LT *first() const { return _first; }
+			LT       *first()       { return _first; }
+			LT const *first() const { return _first; }
 
 			/**
-			 * Insert element into list
+			 * Insert element after specified element into list
+			 *
+			 * \param  le  list element to insert
+			 * \param  at  target position (preceding list element)
 			 */
-			void insert(LT *le)
+			void insert(LT const *le, LT const *at = 0)
 			{
+				/* insert at beginning of the list */
+				if (at == 0) {
 					le->Element::_next = _first;
-				_first = le;
+					_first = const_cast<LT *>(le);
+				} else {
+					le->Element::_next = at->Element::_next;
+					at->Element::_next = const_cast<LT *>(le);
+				}
 			}
 
 			/**
 			 * Remove element from list
 			 */
-			void remove(LT *le)
+			void remove(LT const *le)
 			{
 				if (!_first) return;
 
 				/* if specified element is the first of the list */
-				if (le == _first)
+				if (le == _first) {
 					_first = le->Element::_next;
 
-				else {
+				} else {
 
 					/* search specified element in the list */
 					Element *e = _first;
@@ -119,7 +129,7 @@ namespace Genode {
 
 			List_element(T *object) : _object(object) { }
 
-			T *object() { return _object; }
+			T *object() const { return _object; }
 	};
 }
 

base/src/base/signal/signal.cc

@@ -141,7 +141,7 @@ namespace Genode {
 				Lock::Guard guard(_lock);
 
 				/* search list for context */
-				List_element<Signal_context> *le = _list.first();
+				List_element<Signal_context> const *le = _list.first();
 				for ( ; le; le = le->next()) {
 
 					if (context == le->object()) {

base/src/test/lifetime/main.cc

@@ -32,7 +32,7 @@ void Genode::Volatile_object_base::debug_info() const
 {
 	/* count number of weak pointers pointing to the object */
 	weak_ptr_cnt = 0;
-	for (Weak_ptr_base *curr = _list.first(); curr; curr = curr->next())
+	for (Weak_ptr_base const *curr = _list.first(); curr; curr = curr->next())
 		weak_ptr_cnt++;
 }
 

gems/src/server/d3m/input_service.h

@@ -157,7 +157,7 @@ namespace Input {
 			 *
 			 * \return  total number of available input events
 			 */
-			Genode::size_t flush_sources(Event *dst, Genode::size_t dst_max) const
+			Genode::size_t flush_sources(Event *dst, Genode::size_t dst_max)
 			{
 				Genode::size_t dst_count = 0;
 

libports/src/lib/libc/libc_mmap_registry.h

@@ -48,10 +48,12 @@ class Libc::Mmap_registry
 
 		Genode::Lock mutable _lock;
 
-		Entry *_lookup_by_addr_unsynchronized(void * const start) const
+		/*
+		 * Common for both const and non-const lookup functions
+		 */
+		template <typename ENTRY>
+		static ENTRY *_lookup_by_addr_unsynchronized(ENTRY *curr, void * const start)
 		{
-			Entry *curr = _list.first();
-
 			for (; curr; curr = curr->next())
 				if (curr->start == start)
 					return curr;
@@ -59,6 +61,16 @@ class Libc::Mmap_registry
 			return 0;
 		}
 
+		Entry const *_lookup_by_addr_unsynchronized(void * const start) const
+		{
+			return _lookup_by_addr_unsynchronized(_list.first(), start);
+		}
+
+		Entry *_lookup_by_addr_unsynchronized(void * const start)
+		{
+			return _lookup_by_addr_unsynchronized(_list.first(), start);
+		}
+
 	public:
 
 		void insert(void *start, Genode::size_t len, Plugin *plugin)
@@ -77,7 +89,7 @@ class Libc::Mmap_registry
 		{
 			Genode::Lock::Guard guard(_lock);
 
-			Entry * const e = _lookup_by_addr_unsynchronized(start);
+			Entry const * const e = _lookup_by_addr_unsynchronized(start);
 			return e ? e->plugin : 0;
 		}
 

os/src/init/main.cc

@@ -141,7 +141,7 @@ namespace Init {
 
 			bool is_unique(const char *name) const
 			{
-				Genode::List_element<Child> *curr = first();
+				Genode::List_element<Child> const *curr = first();
 				for (; curr; curr = curr->next())
 					if (curr->object()->has_name(name))
 						return false;
@@ -151,7 +151,7 @@ namespace Init {
 
 			Genode::Server *lookup_server(const char *name) const
 			{
-				Genode::List_element<Child> *curr = first();
+				Genode::List_element<Child> const *curr = first();
 				for (; curr; curr = curr->next())
 					if (curr->object()->has_name(name))
 						return curr->object()->server();

os/src/server/ram_fs/directory.h

@@ -28,7 +28,7 @@ namespace File_system {
 
 			bool has_sub_node_unsynchronized(char const *name) const
 			{
-				Node *sub_node = _entries.first();
+				Node const *sub_node = _entries.first();
 				for (; sub_node; sub_node = sub_node->next())
 					if (strcmp(sub_node->name(), name) == 0)
 						return true;