From 135b98c26456adbfbc72fb12e4753ee0716b1f92 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Tue, 28 Mar 2023 14:18:08 -0400
Subject: list: New generic linked list API

---
 src/list.c | 169 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 169 insertions(+)
 create mode 100644 src/list.c

(limited to 'src/list.c')

diff --git a/src/list.c b/src/list.c
new file mode 100644
index 0000000..dffee19
--- /dev/null
+++ b/src/list.c
@@ -0,0 +1,169 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include "list.h"
+#include <assert.h>
+#include <stddef.h>
+
+void slink_init(struct slink *link) {
+	link->next = NULL;
+}
+
+void slist_init(struct slist *list) {
+	list->head = NULL;
+	list->tail = &list->head;
+}
+
+bool slist_is_empty(const struct slist *list) {
+	return !list->head;
+}
+
+void slist_append(struct slist *list, struct slink *link) {
+	assert(!link->next);
+	*list->tail = link;
+	list->tail = &link->next;
+}
+
+void slist_prepend(struct slist *list, struct slink *link) {
+	assert(!link->next);
+	if (!list->head) {
+		list->tail = &link->next;
+	}
+	link->next = list->head;
+	list->head = link;
+}
+
+void slist_extend(struct slist *dest, struct slist *src) {
+	if (src->head) {
+		*dest->tail = src->head;
+		dest->tail = src->tail;
+		slist_init(src);
+	}
+}
+
+struct slink *slist_pop(struct slist *list) {
+	struct slink *head = list->head;
+	if (!head) {
+		return NULL;
+	}
+
+	list->head = head->next;
+	if (!list->head) {
+		list->tail = &list->head;
+	}
+
+	head->next = NULL;
+	return head;
+}
+
+void slist_sort(struct slist *list, slist_cmp_fn *cmp_fn, const void *ptr) {
+	if (!list->head || !list->head->next) {
+		return;
+	}
+
+	struct slist left, right;
+	slist_init(&left);
+	slist_init(&right);
+
+	// Split
+	for (struct slink *hare = list->head; hare && (hare = hare->next); hare = hare->next) {
+		slist_append(&left, slist_pop(list));
+	}
+	slist_extend(&right, list);
+
+	// Recurse
+	slist_sort(&left, cmp_fn, ptr);
+	slist_sort(&right, cmp_fn, ptr);
+
+	// Merge
+	while (left.head && right.head) {
+		if (cmp_fn(left.head, right.head, ptr)) {
+			slist_append(list, slist_pop(&left));
+		} else {
+			slist_append(list, slist_pop(&right));
+		}
+	}
+	slist_extend(list, &left);
+	slist_extend(list, &right);
+}
+
+void link_init(struct link *link) {
+	link->prev = NULL;
+	link->next = NULL;
+}
+
+void list_init(struct list *list) {
+	list->head = NULL;
+	list->tail = NULL;
+}
+
+bool list_is_empty(const struct list *list) {
+	return !list->head;
+}
+
+void list_append(struct list *list, struct link *link) {
+	list_insert_after(list, list->tail, link);
+}
+
+void list_prepend(struct list *list, struct link *link) {
+	list_insert_after(list, NULL, link);
+}
+
+void list_insert_after(struct list *list, struct link *target, struct link *link) {
+	assert(!list_attached(list, link));
+
+	if (target) {
+		link->prev = target;
+		link->next = target->next;
+	} else {
+		link->next = list->head;
+	}
+
+	if (link->prev) {
+		link->prev->next = link;
+	} else {
+		list->head = link;
+	}
+
+	if (link->next) {
+		link->next->prev = link;
+	} else {
+		list->tail = link;
+	}
+}
+
+void list_remove(struct list *list, struct link *link) {
+	if (link->prev) {
+		assert(list->head != link);
+		link->prev->next = link->next;
+	} else {
+		assert(list->head == link);
+		list->head = link->next;
+	}
+
+	if (link->next) {
+		assert(list->tail != link);
+		link->next->prev = link->prev;
+	} else {
+		assert(list->tail == link);
+		list->tail = link->prev;
+	}
+
+	link->prev = NULL;
+	link->next = NULL;
+}
+
+struct link *list_pop(struct list *list) {
+	struct link *head = list->head;
+	if (!head) {
+		return NULL;
+	}
+
+	list_remove(list, head);
+	return head;
+}
+
+bool list_attached(const struct list *list, const struct link *link) {
+	return link->prev || list->head == link
+		|| link->next || list->tail == link;
+}
-- 
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