This is an example of implementing a list in C language.
Let's implement a bidirectional list using the following two macros.
--list_head, a list manipulation macro often used in the linux kernel --Queue, a BSD-based list manipulation macro
The execution environment is CentOS7 64bit, gcc 4.8.5.
The linux kernel has the following structure and some macros that use this structure to perform list operations.
struct list_head {
struct list_head *next, *prev;
};
It's difficult to understand how it works, but it's a useful macro to learn how to use.
First, get the kernel source code.
# yum install kernel-devel
...
Installation:
kernel-devel.x86_64 0:3.10.0-957.5.1.el7
Has completed!
Since the macro of list is linux / list.h, it will be the following file.
/usr/src/kernels/3.10.0-957.5.1.el7.x86_64/include/linux/list.h
Since linux / list.h is a header file for kernel, if you try to use it as it is in a userland application, compilation errors will occur frequently, which is inconvenient. (~~ It's troublesome to resolve the error ~~)
So I will modify it a little.
$ cp /usr/src/kernels/3.10.0-957.5.1.el7.x86_64/include/linux/list.h .
$ vim list.h
Modification point
--Delete hlist (because it is not used this time) --Replace LIST_POISON1 and LIST_POISON2 with 0xdeadbeef --Replace typeof () with __typeof () --Copy and paste the container_of () macro from linux / kernel.h
#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H
struct list_head {
struct list_head *next, *prev;
};
/**
* container_of - cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*
*/
#define container_of(ptr, type, member) ({ \
const __typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
/*
* Simple doubly linked list implementation.
*
* Some of the internal functions ("__xxx") are useful when
* manipulating whole lists rather than single entries, as
* sometimes we already know the next/prev entries and we can
* generate better code by using them directly rather than
* using the generic single-entry routines.
*/
#define LIST_HEAD_INIT(name) { &(name), &(name) }
#define LIST_HEAD(name) \
struct list_head name = LIST_HEAD_INIT(name)
static inline void INIT_LIST_HEAD(struct list_head *list)
{
list->next = list;
list->prev = list;
}
/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
#ifndef CONFIG_DEBUG_LIST
static inline void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;
}
#else
extern void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next);
#endif
/**
* list_add - add a new entry
* @new: new entry to be added
* @head: list head to add it after
*
* Insert a new entry after the specified head.
* This is good for implementing stacks.
*/
static inline void list_add(struct list_head *new, struct list_head *head)
{
__list_add(new, head, head->next);
}
/**
* list_add_tail - add a new entry
* @new: new entry to be added
* @head: list head to add it before
*
* Insert a new entry before the specified head.
* This is useful for implementing queues.
*/
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}
/*
* Delete a list entry by making the prev/next entries
* point to each other.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
next->prev = prev;
prev->next = next;
}
/**
* list_del - deletes entry from list.
* @entry: the element to delete from the list.
* Note: list_empty() on entry does not return true after this, the entry is
* in an undefined state.
*/
#ifndef CONFIG_DEBUG_LIST
static inline void __list_del_entry(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
}
static inline void list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->next = (struct list_head*)0xdeadbeef;
entry->prev = (struct list_head*)0xdeadbeef;
}
#else
extern void __list_del_entry(struct list_head *entry);
extern void list_del(struct list_head *entry);
#endif
/**
* list_replace - replace old entry by new one
* @old : the element to be replaced
* @new : the new element to insert
*
* If @old was empty, it will be overwritten.
*/
static inline void list_replace(struct list_head *old,
struct list_head *new)
{
new->next = old->next;
new->next->prev = new;
new->prev = old->prev;
new->prev->next = new;
}
static inline void list_replace_init(struct list_head *old,
struct list_head *new)
{
list_replace(old, new);
INIT_LIST_HEAD(old);
}
/**
* list_del_init - deletes entry from list and reinitialize it.
* @entry: the element to delete from the list.
*/
static inline void list_del_init(struct list_head *entry)
{
__list_del_entry(entry);
INIT_LIST_HEAD(entry);
}
/**
* list_move - delete from one list and add as another's head
* @list: the entry to move
* @head: the head that will precede our entry
*/
static inline void list_move(struct list_head *list, struct list_head *head)
{
__list_del_entry(list);
list_add(list, head);
}
/**
* list_move_tail - delete from one list and add as another's tail
* @list: the entry to move
* @head: the head that will follow our entry
*/
static inline void list_move_tail(struct list_head *list,
struct list_head *head)
{
__list_del_entry(list);
list_add_tail(list, head);
}
/**
* list_is_last - tests whether @list is the last entry in list @head
* @list: the entry to test
* @head: the head of the list
*/
static inline int list_is_last(const struct list_head *list,
const struct list_head *head)
{
return list->next == head;
}
/**
* list_empty - tests whether a list is empty
* @head: the list to test.
*/
static inline int list_empty(const struct list_head *head)
{
return head->next == head;
}
/**
* list_empty_careful - tests whether a list is empty and not being modified
* @head: the list to test
*
* Description:
* tests whether a list is empty _and_ checks that no other CPU might be
* in the process of modifying either member (next or prev)
*
* NOTE: using list_empty_careful() without synchronization
* can only be safe if the only activity that can happen
* to the list entry is list_del_init(). Eg. it cannot be used
* if another CPU could re-list_add() it.
*/
static inline int list_empty_careful(const struct list_head *head)
{
struct list_head *next = head->next;
return (next == head) && (next == head->prev);
}
/**
* list_rotate_left - rotate the list to the left
* @head: the head of the list
*/
static inline void list_rotate_left(struct list_head *head)
{
struct list_head *first;
if (!list_empty(head)) {
first = head->next;
list_move_tail(first, head);
}
}
/**
* list_is_singular - tests whether a list has just one entry.
* @head: the list to test.
*/
static inline int list_is_singular(const struct list_head *head)
{
return !list_empty(head) && (head->next == head->prev);
}
static inline void __list_cut_position(struct list_head *list,
struct list_head *head, struct list_head *entry)
{
struct list_head *new_first = entry->next;
list->next = head->next;
list->next->prev = list;
list->prev = entry;
entry->next = list;
head->next = new_first;
new_first->prev = head;
}
/**
* list_cut_position - cut a list into two
* @list: a new list to add all removed entries
* @head: a list with entries
* @entry: an entry within head, could be the head itself
* and if so we won't cut the list
*
* This helper moves the initial part of @head, up to and
* including @entry, from @head to @list. You should
* pass on @entry an element you know is on @head. @list
* should be an empty list or a list you do not care about
* losing its data.
*
*/
static inline void list_cut_position(struct list_head *list,
struct list_head *head, struct list_head *entry)
{
if (list_empty(head))
return;
if (list_is_singular(head) &&
(head->next != entry && head != entry))
return;
if (entry == head)
INIT_LIST_HEAD(list);
else
__list_cut_position(list, head, entry);
}
static inline void __list_splice(const struct list_head *list,
struct list_head *prev,
struct list_head *next)
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
first->prev = prev;
prev->next = first;
last->next = next;
next->prev = last;
}
/**
* list_splice - join two lists, this is designed for stacks
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice(const struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head, head->next);
}
/**
* list_splice_tail - join two lists, each list being a queue
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice_tail(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head->prev, head);
}
/**
* list_splice_init - join two lists and reinitialise the emptied list.
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* The list at @list is reinitialised
*/
static inline void list_splice_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head, head->next);
INIT_LIST_HEAD(list);
}
}
/**
* list_splice_tail_init - join two lists and reinitialise the emptied list
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* Each of the lists is a queue.
* The list at @list is reinitialised
*/
static inline void list_splice_tail_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head->prev, head);
INIT_LIST_HEAD(list);
}
}
/**
* list_entry - get the struct for this entry
* @ptr: the &struct list_head pointer.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*/
#define list_entry(ptr, type, member) \
container_of(ptr, type, member)
/**
* list_first_entry - get the first element from a list
* @ptr: the list head to take the element from.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* Note, that list is expected to be not empty.
*/
#define list_first_entry(ptr, type, member) \
list_entry((ptr)->next, type, member)
/**
* list_last_entry - get the last element from a list
* @ptr: the list head to take the element from.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* Note, that list is expected to be not empty.
*/
#define list_last_entry(ptr, type, member) \
list_entry((ptr)->prev, type, member)
/**
* list_first_entry_or_null - get the first element from a list
* @ptr: the list head to take the element from.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* Note that if the list is empty, it returns NULL.
*/
#define list_first_entry_or_null(ptr, type, member) \
(!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)
/**
* list_next_entry - get the next element in list
* @pos: the type * to cursor
* @member: the name of the list_struct within the struct.
*/
#define list_next_entry(pos, member) \
list_entry((pos)->member.next, __typeof(*(pos)), member)
/**
* list_prev_entry - get the prev element in list
* @pos: the type * to cursor
* @member: the name of the list_struct within the struct.
*/
#define list_prev_entry(pos, member) \
list_entry((pos)->member.prev, __typeof(*(pos)), member)
/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*/
#define list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); pos = pos->next)
/**
* __list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*
* This variant doesn't differ from list_for_each() any more.
* We don't do prefetching in either case.
*/
#define __list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); pos = pos->next)
/**
* list_for_each_prev - iterate over a list backwards
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*/
#define list_for_each_prev(pos, head) \
for (pos = (head)->prev; pos != (head); pos = pos->prev)
/**
* list_for_each_safe - iterate over a list safe against removal of list entry
* @pos: the &struct list_head to use as a loop cursor.
* @n: another &struct list_head to use as temporary storage
* @head: the head for your list.
*/
#define list_for_each_safe(pos, n, head) \
for (pos = (head)->next, n = pos->next; pos != (head); \
pos = n, n = pos->next)
/**
* list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
* @pos: the &struct list_head to use as a loop cursor.
* @n: another &struct list_head to use as temporary storage
* @head: the head for your list.
*/
#define list_for_each_prev_safe(pos, n, head) \
for (pos = (head)->prev, n = pos->prev; \
pos != (head); \
pos = n, n = pos->prev)
/**
* list_for_each_entry - iterate over list of given type
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry(pos, head, member) \
for (pos = list_entry((head)->next, __typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.next, __typeof(*pos), member))
/**
* list_for_each_entry_reverse - iterate backwards over list of given type.
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_reverse(pos, head, member) \
for (pos = list_entry((head)->prev, __typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.prev, __typeof(*pos), member))
/**
* list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
* @pos: the type * to use as a start point
* @head: the head of the list
* @member: the name of the list_struct within the struct.
*
* Prepares a pos entry for use as a start point in list_for_each_entry_continue().
*/
#define list_prepare_entry(pos, head, member) \
((pos) ? : list_entry(head, __typeof(*pos), member))
/**
* list_for_each_entry_continue - continue iteration over list of given type
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Continue to iterate over list of given type, continuing after
* the current position.
*/
#define list_for_each_entry_continue(pos, head, member) \
for (pos = list_entry(pos->member.next, __typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.next, __typeof(*pos), member))
/**
* list_for_each_entry_continue_reverse - iterate backwards from the given point
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Start to iterate over list of given type backwards, continuing after
* the current position.
*/
#define list_for_each_entry_continue_reverse(pos, head, member) \
for (pos = list_entry(pos->member.prev, __typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.prev, __typeof(*pos), member))
/**
* list_for_each_entry_from - iterate over list of given type from the current point
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate over list of given type, continuing from current position.
*/
#define list_for_each_entry_from(pos, head, member) \
for (; &pos->member != (head); \
pos = list_entry(pos->member.next, __typeof(*pos), member))
/**
* list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_entry((head)->next, __typeof(*pos), member), \
n = list_entry(pos->member.next, __typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, __typeof(*n), member))
/**
* list_for_each_entry_safe_continue - continue list iteration safe against removal
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate over list of given type, continuing after current point,
* safe against removal of list entry.
*/
#define list_for_each_entry_safe_continue(pos, n, head, member) \
for (pos = list_entry(pos->member.next, __typeof(*pos), member), \
n = list_entry(pos->member.next, __typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, __typeof(*n), member))
/**
* list_for_each_entry_safe_from - iterate over list from current point safe against removal
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate over list of given type from current point, safe against
* removal of list entry.
*/
#define list_for_each_entry_safe_from(pos, n, head, member) \
for (n = list_entry(pos->member.next, __typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, __typeof(*n), member))
/**
* list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate backwards over list of given type, safe against removal
* of list entry.
*/
#define list_for_each_entry_safe_reverse(pos, n, head, member) \
for (pos = list_entry((head)->prev, __typeof(*pos), member), \
n = list_entry(pos->member.prev, __typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.prev, __typeof(*n), member))
/**
* list_safe_reset_next - reset a stale list_for_each_entry_safe loop
* @pos: the loop cursor used in the list_for_each_entry_safe loop
* @n: temporary storage used in list_for_each_entry_safe
* @member: the name of the list_struct within the struct.
*
* list_safe_reset_next is not safe to use in general if the list may be
* modified concurrently (eg. the lock is dropped in the loop body). An
* exception to this is if the cursor element (pos) is pinned in the list,
* and list_safe_reset_next is called after re-taking the lock and before
* completing the current iteration of the loop body.
*/
#define list_safe_reset_next(pos, n, member) \
n = list_entry(pos->member.next, __typeof(*pos), member)
#endif
Sample list creation, display, rotation, and deletion.
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#include <string.h>
#include <stddef.h>
#include "list.h"
/*Sea fish*/
#define FISH_SARDINE "sardine" /*sardine*/
#define FISH_MACKEREL "mackerel" /*mackerel*/
#define FISH_TUNA "tuna" /*Tuna*/
/*River fish*/
#define FISH_SALMON "salmon" /*salmon*/
#define FISH_SEABASS "seabass" /*Suzuki*/
#define FISH_EEL "eel" /*eel*/
typedef struct {
struct list_head head;
uint32_t count;
} fishlist_t;
typedef struct {
struct list_head list;
uint32_t id;
char name[64];
} fish_t;
static fishlist_t FishSea;
static fishlist_t FishRiver;
/*ID issuance*/
static uint32_t get_id(void)
{
static uint32_t id = 0;
return (++id % UINT32_MAX);
}
/*List initialization*/
static void init_fish_list(void)
{
INIT_LIST_HEAD(&FishSea.head);
FishSea.count = 0;
INIT_LIST_HEAD(&FishRiver.head);
FishRiver.count = 0;
}
/*Add sea fish to list*/
static void add_sea_fish_entry(void)
{
char *fish_name[] = {
FISH_SARDINE,
FISH_MACKEREL,
FISH_TUNA
};
fish_t *fish = NULL;
for (int i = 0; i < sizeof(fish_name)/sizeof(fish_name[0]); i++) {
fish = (fish_t *)malloc(sizeof(fish_t));
if (NULL != fish) {
memset(fish, 0, sizeof(*fish));
snprintf(fish->name, sizeof(fish->name)-1, "%s", fish_name[i]);
fish->id = get_id();
list_add_tail(&fish->list, &FishSea.head);
FishSea.count++;
}
}
}
/*Add river fish to list*/
static void add_river_fish_entry(void)
{
char *fish_name[] = {
FISH_SALMON,
FISH_SEABASS,
FISH_EEL
};
fish_t *fish = NULL;
for (int i = 0; i < sizeof(fish_name)/sizeof(fish_name[0]); i++) {
fish = (fish_t *)malloc(sizeof(fish_t));
if (NULL != fish) {
memset(fish, 0, sizeof(*fish));
snprintf(fish->name, sizeof(fish->name)-1, "%s", fish_name[i]);
fish->id = get_id();
list_add_tail(&fish->list, &FishRiver.head);
FishRiver.count++;
}
}
}
/*Show list of sea fish*/
static void show_sea_fish_entry(void)
{
fish_t *fish = NULL;
fish_t *n = NULL;
printf("----------- show sea fish entry (cnt:%u) ------------\n",
FishSea.count);
list_for_each_entry_safe(fish, n, &(FishSea.head), list) {
printf("id:name = %u:%s\n", fish->id, fish->name);
}
}
/*View a list of river fish*/
static void show_river_fish_entry(void)
{
fish_t *fish = NULL;
fish_t *n = NULL;
printf("----------- show river fish entry (cnt:%u) ------------\n",
FishRiver.count);
list_for_each_entry_safe(fish, n, &(FishRiver.head), list) {
printf("id:name = %u:%s\n", fish->id, fish->name);
}
}
/*Rotate the list of river fish counterclockwise*/
static void rotate_left_sea_fish(void)
{
list_rotate_left(&(FishSea.head));
}
/*Combine river fish with sea fish*/
static void splice_river_to_sea_fish(void)
{
/*Combined with Fish River and joined with Fish Sea*/
list_splice(&(FishRiver.head), &(FishSea.head));
FishSea.count += FishRiver.count;
/*After that, I'm not good at using the list of Fish River*/
INIT_LIST_HEAD(&(FishRiver.head));
FishRiver.count = 0;
}
/*Delete all entries in the saltwater fish list*/
static void del_sea_fish_all(void)
{
fish_t *e = NULL;
while(!list_empty(&(FishSea.head))) {
e = list_first_entry((&FishSea.head), fish_t, list);
list_del(&e->list);
free(e);
e = NULL;
FishSea.count--;
}
}
int main(void)
{
/*List initialization*/
init_fish_list();
/*List of sea fish*/
add_sea_fish_entry();
show_sea_fish_entry();
/*List of river fish*/
add_river_fish_entry();
show_river_fish_entry();
/*Join list(river -> sea) */
splice_river_to_sea_fish();
show_sea_fish_entry();
/*List rotation*/
rotate_left_sea_fish();
show_sea_fish_entry();
/*Delete list*/
del_sea_fish_all();
show_sea_fish_entry();
return 0;
}
$ gcc list.c -std=c99 -o fish_list
$ ./fish_list
----------- show sea fish entry (cnt:3) ------------
id:name = 1:sardine
id:name = 2:mackerel
id:name = 3:tuna
----------- show river fish entry (cnt:3) ------------
id:name = 4:salmon
id:name = 5:seabass
id:name = 6:eel
----------- show sea fish entry (cnt:6) ------------
id:name = 4:salmon
id:name = 5:seabass
id:name = 6:eel
id:name = 1:sardine
id:name = 2:mackerel
id:name = 3:tuna
----------- show sea fish entry (cnt:6) ------------
id:name = 5:seabass
id:name = 6:eel
id:name = 1:sardine
id:name = 2:mackerel
id:name = 3:tuna
id:name = 4:salmon
----------- show sea fish entry (cnt:0) ------------
queue is a macro that manipulates BSD lists, but it can also be used on linux.
This is also a quirk in usage, but it is a useful macro function when implementing a list in a userland application.
However, there are three types of lists that can be used on linux: lists, tail queues, and circular queues. Lists and tails are unidirectional, and circular queues are bidirectional lists.
Let's use the circular queue to replace the list_head macro used in the previous sample program with CIRCLEQ.
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#include <string.h>
#include <stddef.h>
#include <sys/queue.h>
/*Sea fish*/
#define FISH_SARDINE "sardine" /*sardine*/
#define FISH_MACKEREL "mackerel" /*mackerel*/
#define FISH_TUNA "tuna" /*Tuna*/
/*River fish*/
#define FISH_SALMON "salmon" /*salmon*/
#define FISH_SEABASS "seabass" /*Suzuki*/
#define FISH_EEL "eel" /*eel*/
typedef struct {
CIRCLEQ_HEAD(circleq, fish) head;
uint32_t count;
} fishlist_t;
struct circleq *headp; /* Circular queue head. */
typedef struct fish {
uint32_t id;
CIRCLEQ_ENTRY(fish) list;
char name[64];
} fish_t;
static fishlist_t FishSea;
static fishlist_t FishRiver;
/*ID issuance*/
static uint32_t get_id(void)
{
static uint32_t id = 0;
return (++id % UINT32_MAX);
}
/*List initialization*/
static void init_fish_list(void)
{
CIRCLEQ_INIT(&FishSea.head);
FishSea.count = 0;
CIRCLEQ_INIT(&FishRiver.head);
FishRiver.count = 0;
}
/*Add sea fish to list*/
static void add_sea_fish_entry(void)
{
char *fish_name[] = {
FISH_SARDINE,
FISH_MACKEREL,
FISH_TUNA
};
fish_t *fish = NULL;
for (int i = 0; i < sizeof(fish_name)/sizeof(fish_name[0]); i++) {
fish = (fish_t *)malloc(sizeof(fish_t));
if (NULL != fish) {
memset(fish, 0, sizeof(*fish));
snprintf(fish->name, sizeof(fish->name)-1, "%s", fish_name[i]);
fish->id = get_id();
CIRCLEQ_INSERT_TAIL(&FishSea.head, fish, list);
FishSea.count++;
}
}
}
/*Add river fish to list*/
static void add_river_fish_entry(void)
{
char *fish_name[] = {
FISH_SALMON,
FISH_SEABASS,
FISH_EEL
};
fish_t *fish = NULL;
for (int i = 0; i < sizeof(fish_name)/sizeof(fish_name[0]); i++) {
fish = (fish_t *)malloc(sizeof(fish_t));
if (NULL != fish) {
memset(fish, 0, sizeof(*fish));
snprintf(fish->name, sizeof(fish->name)-1, "%s", fish_name[i]);
fish->id = get_id();
CIRCLEQ_INSERT_TAIL(&FishRiver.head, fish, list);
FishRiver.count++;
}
}
}
/*Show list of sea fish*/
static void show_sea_fish_entry(void)
{
fish_t *fish = NULL;
fish_t *n = NULL;
printf("----------- show sea fish entry (cnt:%u) ------------\n",
FishSea.count);
for (fish = (fish_t *)FishSea.head.cqh_first;
fish != (void *)&FishSea.head;
fish = (fish_t *)fish->list.cqe_next) {
printf("id:name = %u:%s\n", fish->id, fish->name);
}
}
/*View a list of river fish*/
static void show_river_fish_entry(void)
{
fish_t *fish = NULL;
fish_t *n = NULL;
printf("----------- show river fish entry (cnt:%u) ------------\n",
FishRiver.count);
for (fish = (fish_t *)FishRiver.head.cqh_first;
fish != (void *)&FishRiver.head;
fish = (fish_t *)fish->list.cqe_next) {
printf("id:name = %u:%s\n", fish->id, fish->name);
}
}
/*Rotate the list of river fish counterclockwise*/
static void rotate_left_sea_fish(void)
{
fish_t *first = (fish_t *)FishSea.head.cqh_first;
CIRCLEQ_REMOVE(&FishSea.head, first, list);
CIRCLEQ_INSERT_TAIL(&FishSea.head, first, list);
}
/*Combine river fish with sea fish*/
static void splice_river_to_sea_fish(void)
{
fish_t *fish = NULL;
/*Combined with Fish River and joined with Fish Sea*/
while (FishRiver.head.cqh_first != (void *)&FishRiver.head) {
fish = (fish_t *)FishRiver.head.cqh_last;
CIRCLEQ_REMOVE(&FishRiver.head, fish, list);
CIRCLEQ_INSERT_HEAD(&FishSea.head, fish, list);
}
FishSea.count += FishRiver.count;
FishRiver.count = 0;
}
/*Delete all entries in the saltwater fish list*/
static void del_sea_fish_all(void)
{
fish_t *fish = NULL;
while (FishSea.head.cqh_first != (void *)&FishSea.head) {
fish = FishSea.head.cqh_first;
CIRCLEQ_REMOVE(&FishSea.head, fish, list);
free(fish);
fish = NULL;
FishSea.count--;
}
}
int main(void)
{
/*List initialization*/
init_fish_list();
/*List of sea fish*/
add_sea_fish_entry();
show_sea_fish_entry();
/*List of river fish*/
add_river_fish_entry();
show_river_fish_entry();
/*Join list(river -> sea) */
splice_river_to_sea_fish();
show_sea_fish_entry();
/*List rotation*/
rotate_left_sea_fish();
show_sea_fish_entry();
/*Delete list*/
del_sea_fish_all();
show_sea_fish_entry();
return 0;
}
$ gcc queue.c -std=c99 -o fish_queue
$ ./fish_queue
----------- show sea fish entry (cnt:3) ------------
id:name = 1:sardine
id:name = 2:mackerel
id:name = 3:tuna
----------- show river fish entry (cnt:3) ------------
id:name = 4:salmon
id:name = 5:seabass
id:name = 6:eel
----------- show sea fish entry (cnt:6) ------------
id:name = 4:salmon
id:name = 5:seabass
id:name = 6:eel
id:name = 1:sardine
id:name = 2:mackerel
id:name = 3:tuna
----------- show sea fish entry (cnt:6) ------------
id:name = 5:seabass
id:name = 6:eel
id:name = 1:sardine
id:name = 2:mackerel
id:name = 3:tuna
id:name = 4:salmon
----------- show sea fish entry (cnt:0) ------------
[Small story] I want to use List or data structure easily in C somehow https://qiita.com/chromabox/items/ea9720422d7a974f6ced
A small sample note of list_head https://qiita.com/kure/items/71057470322b1b636c57
How to use the list provided by the linux kernel http://d.hatena.ne.jp/mmitou/20120626/1340731801
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