[PATCH 06/12] staging: usbip: userspace: add new list API

[Valentina Manea]

Add a new list API from CCAN.

Signed-off-by: Valentina Manea <valentina.manea.m@xxxxxxxxx>
---
 drivers/staging/usbip/userspace/libsrc/Makefile.am |   3 +-
 .../staging/usbip/userspace/libsrc/build_assert.h  |  40 ++
 .../staging/usbip/userspace/libsrc/check_type.h    |  64 +++
 .../staging/usbip/userspace/libsrc/container_of.h  | 109 ++++
 drivers/staging/usbip/userspace/libsrc/list.c      |  43 ++
 drivers/staging/usbip/userspace/libsrc/list.h      | 613 +++++++++++++++++++++
 6 files changed, 871 insertions(+), 1 deletion(-)
 create mode 100644 drivers/staging/usbip/userspace/libsrc/build_assert.h
 create mode 100644 drivers/staging/usbip/userspace/libsrc/check_type.h
 create mode 100644 drivers/staging/usbip/userspace/libsrc/container_of.h
 create mode 100644 drivers/staging/usbip/userspace/libsrc/list.c
 create mode 100644 drivers/staging/usbip/userspace/libsrc/list.h

diff --git a/drivers/staging/usbip/userspace/libsrc/Makefile.am b/drivers/staging/usbip/userspace/libsrc/Makefile.am
index 4921189..294270b 100644
--- a/drivers/staging/usbip/userspace/libsrc/Makefile.am
+++ b/drivers/staging/usbip/userspace/libsrc/Makefile.am
@@ -4,4 +4,5 @@ libusbip_la_LDFLAGS  = -version-info @LIBUSBIP_VERSION@
 
 lib_LTLIBRARIES := libusbip.la
 libusbip_la_SOURCES := names.c names.h usbip_host_driver.c usbip_host_driver.h \
-		       usbip_common.c usbip_common.h vhci_driver.c vhci_driver.h
+		       usbip_common.c usbip_common.h vhci_driver.c vhci_driver.h \
+		       list.c list.h build_assert.h check_type.h container_of.h
diff --git a/drivers/staging/usbip/userspace/libsrc/build_assert.h b/drivers/staging/usbip/userspace/libsrc/build_assert.h
new file mode 100644
index 0000000..b9ecd84
--- /dev/null
+++ b/drivers/staging/usbip/userspace/libsrc/build_assert.h
@@ -0,0 +1,40 @@
+/* CC0 (Public domain) - see LICENSE file for details */
+#ifndef CCAN_BUILD_ASSERT_H
+#define CCAN_BUILD_ASSERT_H
+
+/**
+ * BUILD_ASSERT - assert a build-time dependency.
+ * @cond: the compile-time condition which must be true.
+ *
+ * Your compile will fail if the condition isn't true, or can't be evaluated
+ * by the compiler.  This can only be used within a function.
+ *
+ * Example:
+ *	#include <stddef.h>
+ *	...
+ *	static char *foo_to_char(struct foo *foo)
+ *	{
+ *		// This code needs string to be at start of foo.
+ *		BUILD_ASSERT(offsetof(struct foo, string) == 0);
+ *		return (char *)foo;
+ *	}
+ */
+#define BUILD_ASSERT(cond) \
+	do { (void) sizeof(char [1 - 2*!(cond)]); } while(0)
+
+/**
+ * BUILD_ASSERT_OR_ZERO - assert a build-time dependency, as an expression.
+ * @cond: the compile-time condition which must be true.
+ *
+ * Your compile will fail if the condition isn't true, or can't be evaluated
+ * by the compiler.  This can be used in an expression: its value is "0".
+ *
+ * Example:
+ *	#define foo_to_char(foo)					\
+ *		 ((char *)(foo)						\
+ *		  + BUILD_ASSERT_OR_ZERO(offsetof(struct foo, string) == 0))
+ */
+#define BUILD_ASSERT_OR_ZERO(cond) \
+	(sizeof(char [1 - 2*!(cond)]) - 1)
+
+#endif /* CCAN_BUILD_ASSERT_H */
diff --git a/drivers/staging/usbip/userspace/libsrc/check_type.h b/drivers/staging/usbip/userspace/libsrc/check_type.h
new file mode 100644
index 0000000..a39cc41
--- /dev/null
+++ b/drivers/staging/usbip/userspace/libsrc/check_type.h
@@ -0,0 +1,64 @@
+/* CC0 (Public domain) - see LICENSE file for details */
+#ifndef CCAN_CHECK_TYPE_H
+#define CCAN_CHECK_TYPE_H
+#include "config.h"
+
+/**
+ * check_type - issue a warning or build failure if type is not correct.
+ * @expr: the expression whose type we should check (not evaluated).
+ * @type: the exact type we expect the expression to be.
+ *
+ * This macro is usually used within other macros to try to ensure that a macro
+ * argument is of the expected type.  No type promotion of the expression is
+ * done: an unsigned int is not the same as an int!
+ *
+ * check_type() always evaluates to 0.
+ *
+ * If your compiler does not support typeof, then the best we can do is fail
+ * to compile if the sizes of the types are unequal (a less complete check).
+ *
+ * Example:
+ *	// They should always pass a 64-bit value to _set_some_value!
+ *	#define set_some_value(expr)			\
+ *		_set_some_value((check_type((expr), uint64_t), (expr)))
+ */
+
+/**
+ * check_types_match - issue a warning or build failure if types are not same.
+ * @expr1: the first expression (not evaluated).
+ * @expr2: the second expression (not evaluated).
+ *
+ * This macro is usually used within other macros to try to ensure that
+ * arguments are of identical types.  No type promotion of the expressions is
+ * done: an unsigned int is not the same as an int!
+ *
+ * check_types_match() always evaluates to 0.
+ *
+ * If your compiler does not support typeof, then the best we can do is fail
+ * to compile if the sizes of the types are unequal (a less complete check).
+ *
+ * Example:
+ *	// Do subtraction to get to enclosing type, but make sure that
+ *	// pointer is of correct type for that member.
+ *	#define container_of(mbr_ptr, encl_type, mbr)			\
+ *		(check_types_match((mbr_ptr), &((encl_type *)0)->mbr),	\
+ *		 ((encl_type *)						\
+ *		  ((char *)(mbr_ptr) - offsetof(enclosing_type, mbr))))
+ */
+#if HAVE_TYPEOF
+#define check_type(expr, type)			\
+	((typeof(expr) *)0 != (type *)0)
+
+#define check_types_match(expr1, expr2)		\
+	((typeof(expr1) *)0 != (typeof(expr2) *)0)
+#else
+#include <build_assert.h>
+/* Without typeof, we can only test the sizes. */
+#define check_type(expr, type)					\
+	BUILD_ASSERT_OR_ZERO(sizeof(expr) == sizeof(type))
+
+#define check_types_match(expr1, expr2)				\
+	BUILD_ASSERT_OR_ZERO(sizeof(expr1) == sizeof(expr2))
+#endif /* HAVE_TYPEOF */
+
+#endif /* CCAN_CHECK_TYPE_H */
diff --git a/drivers/staging/usbip/userspace/libsrc/container_of.h b/drivers/staging/usbip/userspace/libsrc/container_of.h
new file mode 100644
index 0000000..4afd0fe
--- /dev/null
+++ b/drivers/staging/usbip/userspace/libsrc/container_of.h
@@ -0,0 +1,109 @@
+/* CC0 (Public domain) - see LICENSE file for details */
+#ifndef CCAN_CONTAINER_OF_H
+#define CCAN_CONTAINER_OF_H
+#include <stddef.h>
+
+#include "config.h"
+#include <check_type.h>
+
+/**
+ * container_of - get pointer to enclosing structure
+ * @member_ptr: pointer to the structure member
+ * @containing_type: the type this member is within
+ * @member: the name of this member within the structure.
+ *
+ * Given a pointer to a member of a structure, this macro does pointer
+ * subtraction to return the pointer to the enclosing type.
+ *
+ * Example:
+ *	struct foo {
+ *		int fielda, fieldb;
+ *		// ...
+ *	};
+ *	struct info {
+ *		int some_other_field;
+ *		struct foo my_foo;
+ *	};
+ *
+ *	static struct info *foo_to_info(struct foo *foo)
+ *	{
+ *		return container_of(foo, struct info, my_foo);
+ *	}
+ */
+#define container_of(member_ptr, containing_type, member)		\
+	 ((containing_type *)						\
+	  ((char *)(member_ptr)						\
+	   - container_off(containing_type, member))			\
+	  + check_types_match(*(member_ptr), ((containing_type *)0)->member))
+
+/**
+ * container_off - get offset to enclosing structure
+ * @containing_type: the type this member is within
+ * @member: the name of this member within the structure.
+ *
+ * Given a pointer to a member of a structure, this macro does
+ * typechecking and figures out the offset to the enclosing type.
+ *
+ * Example:
+ *	struct foo {
+ *		int fielda, fieldb;
+ *		// ...
+ *	};
+ *	struct info {
+ *		int some_other_field;
+ *		struct foo my_foo;
+ *	};
+ *
+ *	static struct info *foo_to_info(struct foo *foo)
+ *	{
+ *		size_t off = container_off(struct info, my_foo);
+ *		return (void *)((char *)foo - off);
+ *	}
+ */
+#define container_off(containing_type, member)	\
+	offsetof(containing_type, member)
+
+/**
+ * container_of_var - get pointer to enclosing structure using a variable
+ * @member_ptr: pointer to the structure member
+ * @container_var: a pointer of same type as this member's container
+ * @member: the name of this member within the structure.
+ *
+ * Given a pointer to a member of a structure, this macro does pointer
+ * subtraction to return the pointer to the enclosing type.
+ *
+ * Example:
+ *	static struct info *foo_to_i(struct foo *foo)
+ *	{
+ *		struct info *i = container_of_var(foo, i, my_foo);
+ *		return i;
+ *	}
+ */
+#if HAVE_TYPEOF
+#define container_of_var(member_ptr, container_var, member) \
+	container_of(member_ptr, typeof(*container_var), member)
+#else
+#define container_of_var(member_ptr, container_var, member)	\
+	((void *)((char *)(member_ptr)	-			\
+		  container_off_var(container_var, member)))
+#endif
+
+/**
+ * container_off_var - get offset of a field in enclosing structure
+ * @container_var: a pointer to a container structure
+ * @member: the name of a member within the structure.
+ *
+ * Given (any) pointer to a structure and a its member name, this
+ * macro does pointer subtraction to return offset of member in a
+ * structure memory layout.
+ *
+ */
+#if HAVE_TYPEOF
+#define container_off_var(var, member)		\
+	container_off(typeof(*var), member)
+#else
+#define container_off_var(var, member)			\
+	((char *)&(var)->member - (char *)(var))
+#endif
+
+#endif /* CCAN_CONTAINER_OF_H */
diff --git a/drivers/staging/usbip/userspace/libsrc/list.c b/drivers/staging/usbip/userspace/libsrc/list.c
new file mode 100644
index 0000000..2717fa3
--- /dev/null
+++ b/drivers/staging/usbip/userspace/libsrc/list.c
@@ -0,0 +1,43 @@
+/* Licensed under BSD-MIT - see LICENSE file for details */
+#include <stdio.h>
+#include <stdlib.h>
+#include "list.h"
+
+static void *corrupt(const char *abortstr,
+		     const struct list_node *head,
+		     const struct list_node *node,
+		     unsigned int count)
+{
+	if (abortstr) {
+		fprintf(stderr,
+			"%s: prev corrupt in node %p (%u) of %p\n",
+			abortstr, node, count, head);
+		abort();
+	}
+	return NULL;
+}
+
+struct list_node *list_check_node(const struct list_node *node,
+				  const char *abortstr)
+{
+	const struct list_node *p, *n;
+	int count = 0;
+
+	for (p = node, n = node->next; n != node; p = n, n = n->next) {
+		count++;
+		if (n->prev != p)
+			return corrupt(abortstr, node, n, count);
+	}
+	/* Check prev on head node. */
+	if (node->prev != p)
+		return corrupt(abortstr, node, node, 0);
+
+	return (struct list_node *)node;
+}
+
+struct list_head *list_check(const struct list_head *h, const char *abortstr)
+{
+	if (!list_check_node(&h->n, abortstr))
+		return NULL;
+	return (struct list_head *)h;
+}
diff --git a/drivers/staging/usbip/userspace/libsrc/list.h b/drivers/staging/usbip/userspace/libsrc/list.h
new file mode 100644
index 0000000..dadb40a
--- /dev/null
+++ b/drivers/staging/usbip/userspace/libsrc/list.h
@@ -0,0 +1,613 @@
+/* Licensed under BSD-MIT - see LICENSE file for details */
+#ifndef CCAN_LIST_H
+#define CCAN_LIST_H
+#include <stdbool.h>
+#include <assert.h>
+#include <container_of.h>
+#include <check_type.h>
+
+/**
+ * struct list_node - an entry in a doubly-linked list
+ * @next: next entry (self if empty)
+ * @prev: previous entry (self if empty)
+ *
+ * This is used as an entry in a linked list.
+ * Example:
+ *	struct child {
+ *		const char *name;
+ *		// Linked list of all us children.
+ *		struct list_node list;
+ *	};
+ */
+struct list_node {
+	struct list_node *next, *prev;
+};
+
+/**
+ * struct list_head - the head of a doubly-linked list
+ * @h: the list_head (containing next and prev pointers)
+ *
+ * This is used as the head of a linked list.
+ * Example:
+ *	struct parent {
+ *		const char *name;
+ *		struct list_head children;
+ *		unsigned int num_children;
+ *	};
+ */
+struct list_head {
+	struct list_node n;
+};
+
+/**
+ * list_check - check head of a list for consistency
+ * @h: the list_head
+ * @abortstr: the location to print on aborting, or NULL.
+ *
+ * Because list_nodes have redundant information, consistency checking between
+ * the back and forward links can be done.  This is useful as a debugging check.
+ * If @abortstr is non-NULL, that will be printed in a diagnostic if the list
+ * is inconsistent, and the function will abort.
+ *
+ * Returns the list head if the list is consistent, NULL if not (it
+ * can never return NULL if @abortstr is set).
+ *
+ * See also: list_check_node()
+ *
+ * Example:
+ *	static void dump_parent(struct parent *p)
+ *	{
+ *		struct child *c;
+ *
+ *		printf("%s (%u children):\n", p->name, p->num_children);
+ *		list_check(&p->children, "bad child list");
+ *		list_for_each(&p->children, c, list)
+ *			printf(" -> %s\n", c->name);
+ *	}
+ */
+struct list_head *list_check(const struct list_head *h, const char *abortstr);
+
+/**
+ * list_check_node - check node of a list for consistency
+ * @n: the list_node
+ * @abortstr: the location to print on aborting, or NULL.
+ *
+ * Check consistency of the list node is in (it must be in one).
+ *
+ * See also: list_check()
+ *
+ * Example:
+ *	static void dump_child(const struct child *c)
+ *	{
+ *		list_check_node(&c->list, "bad child list");
+ *		printf("%s\n", c->name);
+ *	}
+ */
+struct list_node *list_check_node(const struct list_node *n,
+				  const char *abortstr);
+
+#ifdef CCAN_LIST_DEBUG
+#define list_debug(h) list_check((h), __func__)
+#define list_debug_node(n) list_check_node((n), __func__)
+#else
+#define list_debug(h) (h)
+#define list_debug_node(n) (n)
+#endif
+
+/**
+ * LIST_HEAD_INIT - initializer for an empty list_head
+ * @name: the name of the list.
+ *
+ * Explicit initializer for an empty list.
+ *
+ * See also:
+ *	LIST_HEAD, list_head_init()
+ *
+ * Example:
+ *	static struct list_head my_list = LIST_HEAD_INIT(my_list);
+ */
+#define LIST_HEAD_INIT(name) { { &name.n, &name.n } }
+
+/**
+ * LIST_HEAD - define and initialize an empty list_head
+ * @name: the name of the list.
+ *
+ * The LIST_HEAD macro defines a list_head and initializes it to an empty
+ * list.  It can be prepended by "static" to define a static list_head.
+ *
+ * See also:
+ *	LIST_HEAD_INIT, list_head_init()
+ *
+ * Example:
+ *	static LIST_HEAD(my_global_list);
+ */
+#define LIST_HEAD(name) \
+	struct list_head name = LIST_HEAD_INIT(name)
+
+/**
+ * list_head_init - initialize a list_head
+ * @h: the list_head to set to the empty list
+ *
+ * Example:
+ *	...
+ *	struct parent *parent = malloc(sizeof(*parent));
+ *
+ *	list_head_init(&parent->children);
+ *	parent->num_children = 0;
+ */
+static inline void list_head_init(struct list_head *h)
+{
+	h->n.next = h->n.prev = &h->n;
+}
+
+/**
+ * list_add - add an entry at the start of a linked list.
+ * @h: the list_head to add the node to
+ * @n: the list_node to add to the list.
+ *
+ * The list_node does not need to be initialized; it will be overwritten.
+ * Example:
+ *	struct child *child = malloc(sizeof(*child));
+ *
+ *	child->name = "marvin";
+ *	list_add(&parent->children, &child->list);
+ *	parent->num_children++;
+ */
+static inline void list_add(struct list_head *h, struct list_node *n)
+{
+	n->next = h->n.next;
+	n->prev = &h->n;
+	h->n.next->prev = n;
+	h->n.next = n;
+	(void)list_debug(h);
+}
+
+/**
+ * list_add_tail - add an entry at the end of a linked list.
+ * @h: the list_head to add the node to
+ * @n: the list_node to add to the list.
+ *
+ * The list_node does not need to be initialized; it will be overwritten.
+ * Example:
+ *	list_add_tail(&parent->children, &child->list);
+ *	parent->num_children++;
+ */
+static inline void list_add_tail(struct list_head *h, struct list_node *n)
+{
+	n->next = &h->n;
+	n->prev = h->n.prev;
+	h->n.prev->next = n;
+	h->n.prev = n;
+	(void)list_debug(h);
+}
+
+/**
+ * list_empty - is a list empty?
+ * @h: the list_head
+ *
+ * If the list is empty, returns true.
+ *
+ * Example:
+ *	assert(list_empty(&parent->children) == (parent->num_children == 0));
+ */
+static inline bool list_empty(const struct list_head *h)
+{
+	(void)list_debug(h);
+	return h->n.next == &h->n;
+}
+
+/**
+ * list_del - delete an entry from an (unknown) linked list.
+ * @n: the list_node to delete from the list.
+ *
+ * Note that this leaves @n in an undefined state; it can be added to
+ * another list, but not deleted again.
+ *
+ * See also:
+ *	list_del_from()
+ *
+ * Example:
+ *	list_del(&child->list);
+ *	parent->num_children--;
+ */
+static inline void list_del(struct list_node *n)
+{
+	(void)list_debug_node(n);
+	n->next->prev = n->prev;
+	n->prev->next = n->next;
+#ifdef CCAN_LIST_DEBUG
+	/* Catch use-after-del. */
+	n->next = n->prev = NULL;
+#endif
+}
+
+/**
+ * list_del_from - delete an entry from a known linked list.
+ * @h: the list_head the node is in.
+ * @n: the list_node to delete from the list.
+ *
+ * This explicitly indicates which list a node is expected to be in,
+ * which is better documentation and can catch more bugs.
+ *
+ * See also: list_del()
+ *
+ * Example:
+ *	list_del_from(&parent->children, &child->list);
+ *	parent->num_children--;
+ */
+static inline void list_del_from(struct list_head *h, struct list_node *n)
+{
+#ifdef CCAN_LIST_DEBUG
+	{
+		/* Thorough check: make sure it was in list! */
+		struct list_node *i;
+		for (i = h->n.next; i != n; i = i->next)
+			assert(i != &h->n);
+	}
+#endif /* CCAN_LIST_DEBUG */
+
+	/* Quick test that catches a surprising number of bugs. */
+	assert(!list_empty(h));
+	list_del(n);
+}
+
+/**
+ * list_entry - convert a list_node back into the structure containing it.
+ * @n: the list_node
+ * @type: the type of the entry
+ * @member: the list_node member of the type
+ *
+ * Example:
+ *	// First list entry is children.next; convert back to child.
+ *	child = list_entry(parent->children.n.next, struct child, list);
+ *
+ * See Also:
+ *	list_top(), list_for_each()
+ */
+#define list_entry(n, type, member) container_of(n, type, member)
+
+/**
+ * list_top - get the first entry in a list
+ * @h: the list_head
+ * @type: the type of the entry
+ * @member: the list_node member of the type
+ *
+ * If the list is empty, returns NULL.
+ *
+ * Example:
+ *	struct child *first;
+ *	first = list_top(&parent->children, struct child, list);
+ *	if (!first)
+ *		printf("Empty list!\n");
+ */
+#define list_top(h, type, member)					\
+	((type *)list_top_((h), list_off_(type, member)))
+
+static inline const void *list_top_(const struct list_head *h, size_t off)
+{
+	if (list_empty(h))
+		return NULL;
+	return (const char *)h->n.next - off;
+}
+
+/**
+ * list_pop - remove the first entry in a list
+ * @h: the list_head
+ * @type: the type of the entry
+ * @member: the list_node member of the type
+ *
+ * If the list is empty, returns NULL.
+ *
+ * Example:
+ *	struct child *one;
+ *	one = list_pop(&parent->children, struct child, list);
+ *	if (!one)
+ *		printf("Empty list!\n");
+ */
+#define list_pop(h, type, member)					\
+	((type *)list_pop_((h), list_off_(type, member)))
+
+static inline const void *list_pop_(const struct list_head *h, size_t off)
+{
+	struct list_node *n;
+
+	if (list_empty(h))
+		return NULL;
+	n = h->n.next;
+	list_del(n);
+	return (const char *)n - off;
+}
+
+/**
+ * list_tail - get the last entry in a list
+ * @h: the list_head
+ * @type: the type of the entry
+ * @member: the list_node member of the type
+ *
+ * If the list is empty, returns NULL.
+ *
+ * Example:
+ *	struct child *last;
+ *	last = list_tail(&parent->children, struct child, list);
+ *	if (!last)
+ *		printf("Empty list!\n");
+ */
+#define list_tail(h, type, member) \
+	((type *)list_tail_((h), list_off_(type, member)))
+
+static inline const void *list_tail_(const struct list_head *h, size_t off)
+{
+	if (list_empty(h))
+		return NULL;
+	return (const char *)h->n.prev - off;
+}
+
+/**
+ * list_for_each - iterate through a list.
+ * @h: the list_head (warning: evaluated multiple times!)
+ * @i: the structure containing the list_node
+ * @member: the list_node member of the structure
+ *
+ * This is a convenient wrapper to iterate @i over the entire list.  It's
+ * a for loop, so you can break and continue as normal.
+ *
+ * Example:
+ *	list_for_each(&parent->children, child, list)
+ *		printf("Name: %s\n", child->name);
+ */
+#define list_for_each(h, i, member)					\
+	list_for_each_off(h, i, list_off_var_(i, member))
+
+/**
+ * list_for_each_rev - iterate through a list backwards.
+ * @h: the list_head
+ * @i: the structure containing the list_node
+ * @member: the list_node member of the structure
+ *
+ * This is a convenient wrapper to iterate @i over the entire list.  It's
+ * a for loop, so you can break and continue as normal.
+ *
+ * Example:
+ *	list_for_each_rev(&parent->children, child, list)
+ *		printf("Name: %s\n", child->name);
+ */
+#define list_for_each_rev(h, i, member)					\
+	for (i = container_of_var(list_debug(h)->n.prev, i, member);	\
+	     &i->member != &(h)->n;					\
+	     i = container_of_var(i->member.prev, i, member))
+
+/**
+ * list_for_each_safe - iterate through a list, maybe during deletion
+ * @h: the list_head
+ * @i: the structure containing the list_node
+ * @nxt: the structure containing the list_node
+ * @member: the list_node member of the structure
+ *
+ * This is a convenient wrapper to iterate @i over the entire list.  It's
+ * a for loop, so you can break and continue as normal.  The extra variable
+ * @nxt is used to hold the next element, so you can delete @i from the list.
+ *
+ * Example:
+ *	struct child *next;
+ *	list_for_each_safe(&parent->children, child, next, list) {
+ *		list_del(&child->list);
+ *		parent->num_children--;
+ *	}
+ */
+#define list_for_each_safe(h, i, nxt, member)				\
+	list_for_each_safe_off(h, i, nxt, list_off_var_(i, member))
+
+/**
+ * list_next - get the next entry in a list
+ * @h: the list_head
+ * @i: a pointer to an entry in the list.
+ * @member: the list_node member of the structure
+ *
+ * If @i was the last entry in the list, returns NULL.
+ *
+ * Example:
+ *	struct child *second;
+ *	second = list_next(&parent->children, first, list);
+ *	if (!second)
+ *		printf("No second child!\n");
+ */
+#define list_next(h, i, member)						\
+	((list_typeof(i))list_entry_or_null(list_debug(h),		\
+					    (i)->member.next,		\
+					    list_off_var_((i), member)))
+
+/**
+ * list_prev - get the previous entry in a list
+ * @h: the list_head
+ * @i: a pointer to an entry in the list.
+ * @member: the list_node member of the structure
+ *
+ * If @i was the first entry in the list, returns NULL.
+ *
+ * Example:
+ *	first = list_prev(&parent->children, second, list);
+ *	if (!first)
+ *		printf("Can't go back to first child?!\n");
+ */
+#define list_prev(h, i, member)						\
+	((list_typeof(i))list_entry_or_null(list_debug(h),		\
+					    (i)->member.prev,		\
+					    list_off_var_((i), member)))
+
+/**
+ * list_append_list - empty one list onto the end of another.
+ * @to: the list to append into
+ * @from: the list to empty.
+ *
+ * This takes the entire contents of @from and moves it to the end of
+ * @to.  After this @from will be empty.
+ *
+ * Example:
+ *	struct list_head adopter;
+ *
+ *	list_append_list(&adopter, &parent->children);
+ *	assert(list_empty(&parent->children));
+ *	parent->num_children = 0;
+ */
+static inline void list_append_list(struct list_head *to,
+				    struct list_head *from)
+{
+	struct list_node *from_tail = list_debug(from)->n.prev;
+	struct list_node *to_tail = list_debug(to)->n.prev;
+
+	/* Sew in head and entire list. */
+	to->n.prev = from_tail;
+	from_tail->next = &to->n;
+	to_tail->next = &from->n;
+	from->n.prev = to_tail;
+
+	/* Now remove head. */
+	list_del(&from->n);
+	list_head_init(from);
+}
+
+/**
+ * list_prepend_list - empty one list into the start of another.
+ * @to: the list to prepend into
+ * @from: the list to empty.
+ *
+ * This takes the entire contents of @from and moves it to the start
+ * of @to.  After this @from will be empty.
+ *
+ * Example:
+ *	list_prepend_list(&adopter, &parent->children);
+ *	assert(list_empty(&parent->children));
+ *	parent->num_children = 0;
+ */
+static inline void list_prepend_list(struct list_head *to,
+				     struct list_head *from)
+{
+	struct list_node *from_tail = list_debug(from)->n.prev;
+	struct list_node *to_head = list_debug(to)->n.next;
+
+	/* Sew in head and entire list. */
+	to->n.next = &from->n;
+	from->n.prev = &to->n;
+	to_head->prev = from_tail;
+	from_tail->next = to_head;
+
+	/* Now remove head. */
+	list_del(&from->n);
+	list_head_init(from);
+}
+
+/**
+ * list_for_each_off - iterate through a list of memory regions.
+ * @h: the list_head
+ * @i: the pointer to a memory region wich contains list node data.
+ * @off: offset(relative to @i) at which list node data resides.
+ *
+ * This is a low-level wrapper to iterate @i over the entire list, 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 assumtion made is that @i points
+ * to a chunk of memory that at some @offset, relative to @i, contains a
+ * properly filled `struct node_list' which in turn contains pointers to
+ * memory chunks and it's turtles all the way down. Whith all that in mind
+ * remember that given the wrong pointer/offset couple this macro will
+ * happilly 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 list_node'
+ * member(preferably 0), because it allows you not to disclose the type of
+ * @i.
+ *
+ * Example:
+ *	list_for_each_off(&parent->children, child,
+ *				offsetof(struct child, list))
+ *		printf("Name: %s\n", child->name);
+ */
+#define list_for_each_off(h, i, off)                                            \
+	for (i = list_node_to_off_(list_debug(h)->n.next, (off));               \
+	     list_node_from_off_((void *)i, (off)) != &(h)->n;                  \
+	     i = list_node_to_off_(list_node_from_off_((void *)i, (off))->next, \
+				   (off)))
+
+/**
+ * list_for_each_safe_off - iterate through a list of memory regions, maybe
+ * during deletion
+ * @h: the list_head
+ * @i: the pointer to a memory region wich contains list node data.
+ * @nxt: the structure containing the list_node
+ * @off: offset(relative to @i) at which list node data resides.
+ *
+ * For details see `list_for_each_off' and `list_for_each_safe'
+ * descriptions.
+ *
+ * Example:
+ *	list_for_each_safe_off(&parent->children, child,
+ *		next, offsetof(struct child, list))
+ *		printf("Name: %s\n", child->name);
+ */
+#define list_for_each_safe_off(h, i, nxt, off)                                \
+	for (i = list_node_to_off_(list_debug(h)->n.next, (off)),             \
+	     nxt = list_node_to_off_(list_node_from_off_(i, (off))->next,     \
+				     (off));                                  \
+	     list_node_from_off_(i, (off)) != &(h)->n;                        \
+	     i = nxt,                                                         \
+		 nxt = list_node_to_off_(list_node_from_off_(i, (off))->next, \
+					 (off)))
+
+
+/* Other -off variants. */
+#define list_entry_off(n, type, off)		\
+	((type *)list_node_from_off_((n), (off)))
+
+#define list_head_off(h, type, off)		\
+	((type *)list_head_off((h), (off)))
+
+#define list_tail_off(h, type, off)		\
+	((type *)list_tail_((h), (off)))
+
+#define list_add_off(h, n, off)                 \
+	list_add((h), list_node_from_off_((n), (off)))
+
+#define list_del_off(n, off)                    \
+	list_del(list_node_from_off_((n), (off)))
+
+#define list_del_from_off(h, n, off)			\
+	list_del_from(h, list_node_from_off_((n), (off)))
+
+/* Offset helper functions so we only single-evaluate. */
+static inline void *list_node_to_off_(struct list_node *node, size_t off)
+{
+	return (void *)((char *)node - off);
+}
+static inline struct list_node *list_node_from_off_(void *ptr, size_t off)
+{
+	return (struct list_node *)((char *)ptr + off);
+}
+
+/* Get the offset of the member, but make sure it's a list_node. */
+#define list_off_(type, member)					\
+	(container_off(type, member) +				\
+	 check_type(((type *)0)->member, struct list_node))
+
+#define list_off_var_(var, member)			\
+	(container_off_var(var, member) +		\
+	 check_type(var->member, struct list_node))
+
+#if HAVE_TYPEOF
+#define list_typeof(var) typeof(var)
+#else
+#define list_typeof(var) void *
+#endif
+
+/* Returns member, or NULL if at end of list. */
+static inline void *list_entry_or_null(const struct list_head *h,
+				       const struct list_node *n,
+				       size_t off)
+{
+	if (n == &h->n)
+		return NULL;
+	return (char *)n - off;
+}
+#endif /* CCAN_LIST_H */
-- 
1.8.1.2

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