linux-kernel - [PATCH v5 02/11] kbuild: Add list_is_{first,last}, list_size, list_at_index, list_for_each

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Message-Id: <20240920085628.51863-3-ole0811sch@gmail.com>
Date: Fri, 20 Sep 2024 10:56:19 +0200
From: Ole Schuerks <ole0811sch@...il.com>
To: linux-kbuild@...r.kernel.org
Cc: ole0811sch@...il.com,
	jude.gyimah@....de,
	thorsten.berger@....de,
	deltaone@...ian.org,
	jan.sollmann@....de,
	mcgrof@...nel.org,
	masahiroy@...nel.org,
	linux-kernel@...r.kernel.org,
	nathan@...nel.org,
	nicolas@...sle.eu
Subject: [PATCH v5 02/11] kbuild: Add list_is_{first,last}, list_size, list_at_index, list_for_each_from

list_is_first and list_is_last respectively check whether an entry is
the first or last entry of the list. list_size counts the number of
entries. list_at_index retrieves the entry at an index.
list_for_each_from iterates over a list from some entry to the end.

Signed-off-by: Ole Schuerks <ole0811sch@...il.com>
---
 scripts/include/list.h | 71 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/scripts/include/list.h b/scripts/include/list.h
index fea1e2b79063..f7aff1749a0b 100644
--- a/scripts/include/list.h
+++ b/scripts/include/list.h
@@ -169,6 +169,43 @@ static inline int list_empty(const struct list_head *head)
 	return head->next == head;
 }
 
+/**
+ * list_is_first - tests whether @list belongs to the first entry
+ * @list: the entry to test
+ * @head: the head of the list
+ */
+static inline int list_is_first(const struct list_head *list,
+				const struct list_head *head)
+{
+	return list == head->next;
+}
+
+/**
+ * list_is_last - tests whether @list belongs to the last entry
+ * @list: the entry to test
+ * @head: the head of the list
+ */
+static inline int list_is_last(const struct list_head *list,
+			       const struct list_head *head)
+{
+	return list == head->prev;
+}
+
+/**
+ * list_size - counts the number of entries in a list
+ * @head: the list whose entries are counted
+ */
+static inline size_t list_size(const struct list_head *head)
+{
+	size_t ret = 0;
+
+	for (struct list_head *curr = head->next; curr != head;
+	     curr = curr->next)
+		++ret;
+
+	return ret;
+}
+
 /**
  * list_entry - get the struct for this entry
  * @ptr:	the &struct list_head pointer.
@@ -260,6 +297,40 @@ static inline int list_empty(const struct list_head *head)
 	     !list_entry_is_head(pos, head, member);			\
 	     pos = n, n = list_next_entry(n, member))
 
+/**
+ * list_for_each_entry_from - iterate over list of given type starting at a given node
+ * @pos:	the type * to use as a loop cursor.
+ * @start:	the node to start iterating at
+ * @head:	the head for your list.
+ * @member:	the name of the list_head within the struct.
+ */
+#define list_for_each_entry_from(pos, start, head, member)  \
+	for (pos = list_entry(start, typeof(*pos), member); \
+	     !list_entry_is_head(pos, head, member);        \
+	     pos = list_next_entry(pos, member))
+
+/**
+ * list_at_index - retrieve the entry at index i in O(n)
+ * @i:		index of entry to retrieve.
+ * @head:	the head for your list.
+ * @type:	the type of the struct the entries are embedded in.
+ * @member:	the name of the list_head within the struct.
+ */
+#define list_at_index(i, head, type, member)               \
+	({                                                 \
+		type *__pos;                               \
+		size_t __counter = 0;                      \
+		list_for_each_entry(__pos, head, member) { \
+			if (__counter++ == i)              \
+				break;                     \
+			if (__pos->member.next == head) {  \
+				__pos = NULL;              \
+				break;                     \
+			}                                  \
+		}                                          \
+		__pos;                                     \
+	})
+
 /*
  * Double linked lists with a single pointer list head.
  * Mostly useful for hash tables where the two pointer list head is
-- 
2.39.2