safe_list: add a new linked list variant

Use this linked list implementation as a replacement for list.h if you
want to allow deleting arbitrary list entries from within one or more
recursive iterator calling context

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

CMakeLists.txt

@@ -19,7 +19,7 @@ IF(JSONC_FOUND)
   INCLUDE_DIRECTORIES(${JSONC_INCLUDE_DIRS})
 ENDIF()
 
-SET(SOURCES avl.c avl-cmp.c blob.c blobmsg.c uloop.c usock.c ustream.c ustream-fd.c vlist.c utils.c)
+SET(SOURCES avl.c avl-cmp.c blob.c blobmsg.c uloop.c usock.c ustream.c ustream-fd.c vlist.c utils.c safe_list.c)
 
 ADD_LIBRARY(ubox SHARED ${SOURCES})
 

safe_list.c

@@ -0,0 +1,114 @@
+/*
+ * safe_list - linked list protected against recursive iteration with deletes
+ *
+ * Copyright (C) 2013 Felix Fietkau <nbd@openwrt.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "safe_list.h"
+
+struct safe_list_iterator {
+	struct safe_list_iterator **head;
+	struct safe_list_iterator *next_i;
+	struct safe_list *next;
+};
+
+static void
+__safe_list_set_iterator(struct safe_list *list,
+			 struct safe_list_iterator *i)
+{
+	struct safe_list_iterator *next_i;
+	struct safe_list *next;
+
+	next = list_entry(list->list.next, struct safe_list, list);
+	next_i = next->i;
+
+	next->i = i;
+	i->next = next;
+	i->head = &next->i;
+
+	i->next_i = next_i;
+	if (next_i)
+		next_i->head = &i->next_i;
+}
+
+static void
+__safe_list_del_iterator(struct safe_list_iterator *i)
+{
+	*i->head = i->next_i;
+	if (i->next_i)
+		i->next_i->head = i->head;
+}
+
+static void
+__safe_list_move_iterator(struct safe_list *list,
+			  struct safe_list_iterator *i)
+{
+	__safe_list_del_iterator(i);
+	__safe_list_set_iterator(list, i);
+}
+
+int safe_list_for_each(struct safe_list *head,
+		       int (*cb)(void *ctx, struct safe_list *list),
+		       void *ctx)
+{
+	struct safe_list_iterator i;
+	struct safe_list *cur;
+	int ret = 0;
+
+	for (cur = list_entry(head->list.next, struct safe_list, list),
+	     __safe_list_set_iterator(cur, &i);
+	     cur != head;
+	     cur = i.next, __safe_list_move_iterator(cur, &i)) {
+		ret = cb(ctx, cur);
+		if (ret)
+			break;
+	}
+
+	__safe_list_del_iterator(&i);
+	return ret;
+}
+
+void safe_list_add(struct safe_list *list, struct safe_list *head)
+{
+	list->i = NULL;
+	list_add_tail(&list->list, &head->list);
+}
+
+void safe_list_del(struct safe_list *list)
+{
+	struct safe_list_iterator *i, *next_i, **tail;
+	struct safe_list *next;
+
+	next = list_entry(list->list.next, struct safe_list, list);
+	list_del(&list->list);
+
+	if (!list->i)
+		return;
+
+	next_i = next->i;
+	tail = &next->i;
+
+	for (i = list->i; i; i = i->next_i) {
+		tail = &i->next_i;
+		i->next = next;
+	}
+
+	next->i = list->i;
+	list->i->head = &next->i;
+	*tail = next_i;
+	next_i->head = tail;
+
+	list->i = NULL;
+}

safe_list.h

@@ -0,0 +1,56 @@
+/*
+ * safe_list - linked list protected against recursive iteration with deletes
+ *
+ * Copyright (C) 2013 Felix Fietkau <nbd@openwrt.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Use this linked list implementation as a replacement for list.h if you
+ * want to allow deleting arbitrary list entries from within one or more
+ * recursive iterator calling context
+ */
+
+#ifndef __LIBUBOX_SAFE_LIST_H
+#define __LIBUBOX_SAFE_LIST_H
+
+#include <stdbool.h>
+#include "list.h"
+#include "utils.h"
+
+struct safe_list;
+struct safe_list_terator;
+
+struct safe_list {
+	struct list_head list;
+	struct safe_list_iterator *i;
+};
+
+int safe_list_for_each(struct safe_list *list,
+		       int (*cb)(void *ctx, struct safe_list *list),
+		       void *ctx);
+
+void safe_list_add(struct safe_list *list, struct safe_list *head);
+void safe_list_del(struct safe_list *list);
+
+#define INIT_SAFE_LIST(_head) \
+	do { \
+		INIT_LIST_HEAD(_head.list); \
+		(_head)->i = NULL; \
+	} while (0)
+
+#define SAFE_LIST_INIT(_name) { LIST_HEAD_INIT(_name.list), NULL }
+#define SAFE_LIST(_name)	struct safe_list _name = SAFE_LIST_INIT(_name)
+
+#endif