AFAIK there's no "proper" (as in "same API as ccan/list") singly-linked
list implementation in CCAN.
The appended is obviously incomplete (e.g. no debug, no deletions) but as is
it gives me a ~15% speedup when doing a BFS traversal of a large graph, whose
edges are represented as an adjacency list.
- Should we have something like this? I tried adding a for_each macro to
lqueue but that was just too ugly to live. Yes, one could just use *next
pointers in the original code, but then there's no list_for_each, and
no trivial update path to a doubly-linked list should the need arise.
- If so, should it be a separate module, a submodule under list, or just
a header next to list.h?
I'm just dropping slist.h here due to laziness; I like the idea of having
both singly and doubly-linked list implementations under list/ though,
so that they can share code and are less likely be overlooked by users.
Signed-off-by: Emilio G. Cota <c...@braap.org>
---
ccan/list/slist.h | 195 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 195 insertions(+)
create mode 100644 ccan/list/slist.h
diff --git a/ccan/list/slist.h b/ccan/list/slist.h
new file mode 100644
index 0000000..d0eae32
--- /dev/null
+++ b/ccan/list/slist.h
@@ -0,0 +1,195 @@
+/* Licensed under BSD-MIT - see LICENSE file for details */
+#ifndef CCAN_SLIST_H
+#define CCAN_SLIST_H
+//#define CCAN_SLIST_DEBUG 1
+#include <ccan/str/str.h>
+#include <ccan/container_of/container_of.h>
+#include <ccan/check_type/check_type.h>
+
+/**
+ * struct slist_node - an entry in a singly-linked list
+ * @next: next entry (self if empty)
+ *
+ * This is used as an entry in a singly-linked list.
+ * Example:
+ * struct child {
+ * const char *name;
+ * // Linked list of all us children.
+ * struct slist_node slist;
+ * };
+ */
+struct slist_node {
+ struct slist_node *next;
+};
+
+/**
+ * struct slist_head - the head of a singly-linked list
+ * @h: the slist_head (containing next pointer)
+ *
+ * This is used as the head of a singly-linked list.
+ * Example:
+ * struct parent {
+ * const char *name;
+ * struct slist_head children;
+ * unsigned int num_children;
+ * };
+ */
+struct slist_head {
+ struct slist_node n;
+};
+
+#define SLIST_LOC __FILE__ ":" stringify(__LINE__)
+#ifdef CCAN_SLIST_DEBUG
+#define slist_debug(h, loc) slist_check((h), loc)
+#define slist_debug_node(n, loc) slist_check_node((n), loc)
+#else
+#define slist_debug(h, loc) ((void)loc, h)
+#define slist_debug_node(n, loc) ((void)loc, n)
+#endif
+
+/**
+ * SLIST_HEAD_INIT - initializer for an empty slist_head
+ * @name: the name of the slist.
+ *
+ * Explicit initializer for an empty slist.
+ *
+ * See also:
+ * SLIST_HEAD, slist_head_init()
+ *
+ * Example:
+ * static struct slist_head my_slist = SLIST_HEAD_INIT(my_slist);
+ */
+#define SLIST_HEAD_INIT(name) { { &(name).n } }
+
+/**
+ * SLIST_HEAD - define and initialize an empty slist_head
+ * @name: the name of the slist.
+ *
+ * The SLIST_HEAD macro defines a slist_head and initializes it to an empty
+ * slist. It can be prepended by "static" to define a static slist_head.
+ *
+ * See also:
+ * SLIST_HEAD_INIT, slist_head_init()
+ *
+ * Example:
+ * static SLIST_HEAD(my_global_slist);
+ */
+#define SLIST_HEAD(name) \
+ struct slist_head name = SLIST_HEAD_INIT(name)
+
+/**
+ * slist_head_init - initialize a slist_head
+ * @h: the slist_head to set to the empty slist
+ *
+ * Example:
+ * ...
+ * struct parent *parent = malloc(sizeof(*parent));
+ *
+ * slist_head_init(&parent->children);
+ * parent->num_children = 0;
+ */
+static inline void slist_head_init(struct slist_head *h)
+{
+ h->n.next = &h->n;
+}
+
+/**
+ * slist_add - add an entry at the start of a linked list.
+ * @h: the slist_head to add the node to
+ * @n: the slist_node to add to the list.
+ *
+ * The slist_node does not need to be initialized; it will be overwritten.
+ * Example:
+ * struct child *child = malloc(sizeof(*child));
+ *
+ * child->name = "marvin";
+ * slist_add(&parent->children, &child->slist);
+ * parent->num_children++;
+ */
+#define slist_add(h, n) slist_add_(h, n, SLIST_LOC)
+static inline void slist_add_(struct slist_head *h,
+ struct slist_node *n,
+ const char *abortstr)
+{
+ n->next = h->n.next;
+ h->n.next = n;
+}
+
+/**
+ * slist_for_each - iterate through a slist.
+ * @h: the slist_head (warning: evaluated multiple times!)
+ * @i: the structure containing the slist_node
+ * @member: the slist_node member of the structure
+ *
+ * This is a convenient wrapper to iterate @i over the entire slist. It's
+ * a for loop, so you can break and continue as normal.
+ *
+ * Example:
+ * slist_for_each(&parent->children, child, slist)
+ * printf("Name: %s\n", child->name);
+ */
+#define slist_for_each(h, i, member) \
+ slist_for_each_off(h, i, slist_off_var_(i, member))
+
+/**
+ * slist_for_each_off - iterate through a slist of memory regions.
+ * @h: the slist_head
+ * @i: the pointer to a memory region wich contains slist node data.
+ * @off: offset(relative to @i) at which slist node data resides.
+ *
+ * This is a low-level wrapper to iterate @i over the entire slist, used to
+ * implement all oher, more high-level, for-each constructs. It's a for loop,
+ * so you can break and continue as normal.
+ *
+ * WARNING! Being the low-level macro that it is, this wrapper doesn't know
+ * nor care about the type of @i. The only assumption made is that @i points
+ * to a chunk of memory that at some @offset, relative to @i, contains a
+ * properly filled `struct slist_node' which in turn contains pointers to
+ * memory chunks and it's turtles all the way down. With all that in mind
+ * remember that given the wrong pointer/offset couple this macro will
+ * happily churn all you memory untill SEGFAULT stops it, in other words
+ * caveat emptor.
+ *
+ * It is worth mentioning that one of legitimate use-cases for that wrapper
+ * is operation on opaque types with known offset for `struct slist_node'
+ * member(preferably 0), because it allows you not to disclose the type of
+ * @i.
+ *
+ * Example:
+ * slist_for_each_off(&parent->children, child,
+ * offsetof(struct child, slist))
+ * printf("Name: %s\n", child->name);
+ */
+#define slist_for_each_off(h, i, off) \
+ for (i = slist_node_to_off_(slist_debug(h, SLIST_LOC)->n.next, \
+ (off)); \
+ slist_node_from_off_((void *)i, (off)) != &(h)->n; \
+ i = slist_node_to_off_(slist_node_from_off_((void *)i, \
+ (off))->next, (off)))
+
+/* Offset helper functions so we only single-evaluate. */
+static inline void *slist_node_to_off_(struct slist_node *node, size_t off)
+{
+ return (void *)((char *)node - off);
+}
+static inline struct slist_node *slist_node_from_off_(void *ptr, size_t off)
+{
+ return (struct slist_node *)((char *)ptr + off);
+}
+
+/* Get the offset of the member, but make sure it's a slist_node. */
+#define slist_off_(type, member) \
+ (container_off(type, member) + \
+ check_type(((type *)0)->member, struct slist_node))
+
+#define slist_off_var_(var, member) \
+ (container_off_var(var, member) + \
+ check_type(var->member, struct slist_node))
+
+#if HAVE_TYPEOF
+#define slist_typeof(var) typeof(var)
+#else
+#define slist_typeof(var) void *
+#endif
+
+#endif /* CCAN_SLIST_H */
--
2.5.0
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