Add hlist and hashtable from Linux kernel
For more than a decade we've used the linuxlist.h for double-linked
lists. Let's also add the hlist (double-linked lists with single
pointer sized head, and the hashtable that builds on top of it.
This reflects the versions included in Linux 5.8 with some modifications
to make them build in userspace (remove RCU versions, adjust for
userspace include files and types, convert to doxygen).
Change-Id: I8ef73a62fe9846ce45058eb21cf999dd3eed5741
diff --git a/include/osmocom/core/linuxlist.h b/include/osmocom/core/linuxlist.h
index 867605e..2c3a0a4 100644
--- a/include/osmocom/core/linuxlist.h
+++ b/include/osmocom/core/linuxlist.h
@@ -16,6 +16,7 @@
* \file linuxlist.h */
#include <stddef.h>
+#include <stdbool.h>
#ifndef inline
#define inline __inline__
@@ -393,6 +394,252 @@
return i;
}
+
+
+/*! Double linked lists with a single pointer list head.
+ * Mostly useful for hash tables where the two pointer list head is
+ * too wasteful.
+ * You lose the ability to access the tail in O(1).
+ */
+
+struct hlist_head {
+ struct hlist_node *first;
+};
+
+struct hlist_node {
+ struct hlist_node *next, **pprev;
+};
+
+#define HLIST_HEAD_INIT { .first = NULL }
+#define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
+#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
+static inline void INIT_HLIST_NODE(struct hlist_node *h)
+{
+ h->next = NULL;
+ h->pprev = NULL;
+}
+
+#define READ_ONCE(x) x
+#define WRITE_ONCE(a, b) a = b
+
+/*! Has node been removed from list and reinitialized?.
+ * \param[in] h: Node to be checked
+ * \return 1 if node is unhashed; 0 if not
+ *
+ * Not that not all removal functions will leave a node in unhashed
+ * state. For example, hlist_nulls_del_init_rcu() does leave the
+ * node in unhashed state, but hlist_nulls_del() does not.
+ */
+static inline int hlist_unhashed(const struct hlist_node *h)
+{
+ return !h->pprev;
+}
+
+/*! Version of hlist_unhashed for lockless use.
+ * \param[in] n Node to be checked
+ * \return 1 if node is unhashed; 0 if not
+ *
+ * This variant of hlist_unhashed() must be used in lockless contexts
+ * to avoid potential load-tearing. The READ_ONCE() is paired with the
+ * various WRITE_ONCE() in hlist helpers that are defined below.
+ */
+static inline int hlist_unhashed_lockless(const struct hlist_node *h)
+{
+ return !READ_ONCE(h->pprev);
+}
+
+/*!Is the specified hlist_head structure an empty hlist?.
+ * \param[in] h Structure to check.
+ * \return 1 if hlist is empty; 0 if not
+ */
+static inline int hlist_empty(const struct hlist_head *h)
+{
+ return !READ_ONCE(h->first);
+}
+
+static inline void __hlist_del(struct hlist_node *n)
+{
+ struct hlist_node *next = n->next;
+ struct hlist_node **pprev = n->pprev;
+
+ WRITE_ONCE(*pprev, next);
+ if (next)
+ WRITE_ONCE(next->pprev, pprev);
+}
+
+/*! Delete the specified hlist_node from its list.
+ * \param[in] n: Node to delete.
+ *
+ * Note that this function leaves the node in hashed state. Use
+ * hlist_del_init() or similar instead to unhash @n.
+ */
+static inline void hlist_del(struct hlist_node *n)
+{
+ __hlist_del(n);
+ n->next = LLIST_POISON1;
+ n->pprev = LLIST_POISON2;
+}
+
+/*! Delete the specified hlist_node from its list and initialize.
+ * \param[in] n Node to delete.
+ *
+ * Note that this function leaves the node in unhashed state.
+ */
+static inline void hlist_del_init(struct hlist_node *n)
+{
+ if (!hlist_unhashed(n)) {
+ __hlist_del(n);
+ INIT_HLIST_NODE(n);
+ }
+}
+
+/*! add a new entry at the beginning of the hlist.
+ * \param[in] n new entry to be added
+ * \param[in] h hlist head to add it after
+ *
+ * Insert a new entry after the specified head.
+ * This is good for implementing stacks.
+ */
+static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
+{
+ struct hlist_node *first = h->first;
+ WRITE_ONCE(n->next, first);
+ if (first)
+ WRITE_ONCE(first->pprev, &n->next);
+ WRITE_ONCE(h->first, n);
+ WRITE_ONCE(n->pprev, &h->first);
+}
+
+/*! add a new entry before the one specified.
+ * @n: new entry to be added
+ * @next: hlist node to add it before, which must be non-NULL
+ */
+static inline void hlist_add_before(struct hlist_node *n,
+ struct hlist_node *next)
+{
+ WRITE_ONCE(n->pprev, next->pprev);
+ WRITE_ONCE(n->next, next);
+ WRITE_ONCE(next->pprev, &n->next);
+ WRITE_ONCE(*(n->pprev), n);
+}
+
+/*! add a new entry after the one specified
+ * \param[in] n new entry to be added
+ * \param[in] prev hlist node to add it after, which must be non-NULL
+ */
+static inline void hlist_add_behind(struct hlist_node *n,
+ struct hlist_node *prev)
+{
+ WRITE_ONCE(n->next, prev->next);
+ WRITE_ONCE(prev->next, n);
+ WRITE_ONCE(n->pprev, &prev->next);
+
+ if (n->next)
+ WRITE_ONCE(n->next->pprev, &n->next);
+}
+
+/*! create a fake hlist consisting of a single headless node.
+ * \param[in] n Node to make a fake list out of
+ *
+ * This makes @n appear to be its own predecessor on a headless hlist.
+ * The point of this is to allow things like hlist_del() to work correctly
+ * in cases where there is no list.
+ */
+static inline void hlist_add_fake(struct hlist_node *n)
+{
+ n->pprev = &n->next;
+}
+
+/*! Is this node a fake hlist?.
+ * \param[in] h Node to check for being a self-referential fake hlist.
+ */
+static inline bool hlist_fake(struct hlist_node *h)
+{
+ return h->pprev == &h->next;
+}
+
+/*!is node the only element of the specified hlist?.
+ * \param[in] n Node to check for singularity.
+ * \param[in] h Header for potentially singular list.
+ *
+ * Check whether the node is the only node of the head without
+ * accessing head, thus avoiding unnecessary cache misses.
+ */
+static inline bool
+hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
+{
+ return !n->next && n->pprev == &h->first;
+}
+
+/*! Move an hlist.
+ * \param[in] old hlist_head for old list.
+ * \param[in] new hlist_head for new list.
+ *
+ * Move a list from one list head to another. Fixup the pprev
+ * reference of the first entry if it exists.
+ */
+static inline void hlist_move_list(struct hlist_head *old,
+ struct hlist_head *new)
+{
+ new->first = old->first;
+ if (new->first)
+ new->first->pprev = &new->first;
+ old->first = NULL;
+}
+
+#define hlist_entry(ptr, type, member) container_of(ptr,type,member)
+
+#define hlist_for_each(pos, head) \
+ for (pos = (head)->first; pos ; pos = pos->next)
+
+#define hlist_for_each_safe(pos, n, head) \
+ for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
+ pos = n)
+
+#define hlist_entry_safe(ptr, type, member) \
+ ({ typeof(ptr) ____ptr = (ptr); \
+ ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
+ })
+
+/*! iterate over list of given type.
+ * \param[out] pos the type * to use as a loop cursor.
+ * \param[in] head the head for your list.
+ * \param[in] member the name of the hlist_node within the struct.
+ */
+#define hlist_for_each_entry(pos, head, member) \
+ for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
+ pos; \
+ pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
+
+/*! iterate over a hlist continuing after current point.
+ * \param[out] pos the type * to use as a loop cursor.
+ * \param[in] member the name of the hlist_node within the struct.
+ */
+#define hlist_for_each_entry_continue(pos, member) \
+ for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
+ pos; \
+ pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
+
+/*! iterate over a hlist continuing from current point.
+ * \param[out] pos the type * to use as a loop cursor.
+ * \param[in] member the name of the hlist_node within the struct.
+ */
+#define hlist_for_each_entry_from(pos, member) \
+ for (; pos; \
+ pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
+
+/*! hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry.
+ * \param[out] pos the type * to use as a loop cursor.
+ * \param[out] n a &struct hlist_node to use as temporary storage
+ * \param[in] head the head for your list.
+ * \param[in] member the name of the hlist_node within the struct
+ */
+#define hlist_for_each_entry_safe(pos, n, head, member) \
+ for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
+ pos && ({ n = pos->member.next; 1; }); \
+ pos = hlist_entry_safe(n, typeof(*pos), member))
+
+
/*!
* @}
*/