内核链表

一、特性

内核链表：双向循环有头链表

组成：将链表的结点作为结构体成员存在 ，只放指向前驱结点和后继结点的指针

offsetof 获取结构体中的成员到结构体开头中的偏移量

container_of通过偏移量获取结构体首地址

但应用层不能使用上述两个宏，处理方法：将节点作为结构体第一个成员（结构体第一个成员首地址为结构体的地址）

注： 结点将作为结点保存在结构体中，不能定义为指针。

二、内核链表使用示例：

klink.h

#ifndef __KLINK_H__
#define __KLINK_H__

#include <pthread.h>

typedef int (*CMP_t)(void *, void *);

typedef struct knode
{
	struct knode *ppre;
	struct knode *pnext;
}KNode_t;


typedef struct klink
{
	KNode_t *phead;
	int clen;
	pthread_mutex_t mutex;
}KLink_t;


extern int push_klink_head(KLink_t *pklink, void *p);
extern KLink_t *create_klink();
extern void klink_for_each(KLink_t *pklink, void (*pfun)(void *));
extern KNode_t *find_klink(KLink_t *pklink, void * t, CMP_t pfun);
extern int pop_klink_head(KLink_t *pklink);
extern int is_empty_klink(KLink_t *pklink);
extern void destroy_klink(KLink_t *pklink);

#endif

link.c

#include "klink.h"
#include <stdio.h>
#include <stdlib.h>

KLink_t *create_klink()
{
	KLink_t *pklink = malloc(sizeof(KLink_t));
	if (NULL == pklink)
	{
		perror("fail malloc");
		return NULL;

	}
	pklink->phead = NULL;
	pklink->clen = 0;
	pthread_mutex_init(&(pklink->mutex), NULL);

	return pklink;
}


int push_klink_head(KLink_t *pklink, void *p)
{
	KNode_t *pnode = (KNode_t *)p;
	pnode->pnext = NULL;
	pnode->ppre = NULL;

	pnode->pnext = pklink->phead;
	if (pklink->phead != NULL)
	{
		pklink->phead->ppre = pnode;
	}
	pklink->phead = pnode;

	pklink->clen++;

	return 0;
}

void klink_for_each(KLink_t *pklink, void (*pfun)(void *))
{
	KNode_t *pnode = pklink->phead;
	while (pnode != NULL)
	{
		pfun(pnode);
		pnode = pnode->pnext;
	}
	printf("\n");
}

KNode_t *find_klink(KLink_t *pklink, void *t, CMP_t pfun)
{
	KNode_t *pnode = pklink->phead;
	while (pnode != NULL)
	{
		if (pfun(t, pnode))
		{
			return pnode;
		}
		pnode = pnode->pnext;
	}
	
	return NULL;
}

int is_empty_klink(KLink_t *pklink)
{
	return NULL == pklink->phead;
}


int pop_klink_head(KLink_t *pklink)
{
	if (is_empty_klink(pklink))
		return 0;

	KNode_t *pdel = pklink->phead;
	pklink->phead = pdel->pnext;
	if (pklink->phead != NULL)
	{
		pklink->phead->ppre = NULL;
	}
	free(pdel);
	pklink->clen--;

	return 1;
}

void destroy_klink(KLink_t *pklink)
{
	while (!is_empty_klink(pklink))
	{
		pop_klink_head(pklink);
	}
	free(pklink);
}

flight.c

#include "flight.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>


struct passager *create_passager(char *name, int flt_num, int sit_num, char card)
{
	struct passager *p = malloc(sizeof(struct passager));
	if (NULL == p)
	{
		perror("fail malloc");
		return NULL;
	}
	
	strcpy(p->name, name);
	p->flt_num = flt_num;
	p->sit_num = sit_num;
	p->card = card;
	
	return p;
}

void print_passager(void *pnode)
{
	struct passager *p = (struct passager *)pnode;
	printf("%s %d %d %c\n", p->name, p->flt_num, p->sit_num, p->card);
}

struct flight *create_flight(int flt_num, char *src, char *dst)
{
	struct flight *f = malloc(sizeof(struct flight));
	if (NULL == f)
	{
		perror("fail malloc");
		return NULL;
	}
	
	f->flt_num = flt_num;
	strcpy(f->src, src);
	strcpy(f->dst, dst);
	
	return f;
}

void print_flight(void *pnode)
{
	struct flight *f = (struct flight *)pnode;
	printf("%d %s %s\n", f->flt_num, f->src, f->dst);
}

int compare_by_card(void *t, void *pnode)
{
	struct passager *p = (struct passager *)pnode;
	if (p->card == *((char *)t))
	{
		return 1;
	}
	return 0;
}

flight.h

#ifndef __FLIGHT_H__
#define __FLIGHT_H__

#include "klink.h"

struct passager
{
	KNode_t node;
	char name[64];
	int flt_num;
	int sit_num;
	char card;
};

struct flight
{
	KNode_t node;
	int flt_num;
	char src[64];
	char dst[32];
};

extern struct passager *create_passager(char *name, int flt_num, int sit_num, char card);
extern void print_passager(void *pnode);
extern struct flight *create_flight(int flt_num, char *src, char *dst);
extern void print_flight(void *pnode);
extern int compare_by_card(void *t, void *pnode);

#endif

main.c

#include "klink.h"
#include "flight.h"
#include <stdio.h>


int main(int argc, const char *argv[])
{
	KLink_t *ppasslink = create_klink();	
	if (NULL == ppasslink)
	{
		return -1;
	}
	
	struct passager *ppass = create_passager("zhangsan", 2024, 1, 'r');
	push_klink_head(ppasslink, ppass);

	ppass = create_passager("lisi", 2024, 2, 'g');
	push_klink_head(ppasslink, ppass);

	ppass = create_passager("wanger", 2024, 3, 'y');
	push_klink_head(ppasslink, ppass);

	klink_for_each(ppasslink, print_passager);
	
	char card = 'r';
	KNode_t *ptmp = find_klink(ppasslink, &card, compare_by_card);
	if (ptmp != NULL)
	{
		print_passager(ptmp);
	}



	KLink_t *pfltlink = create_klink();
	if (NULL == pfltlink)
	{
		return -1;
	}