单向链表-C语言实现

只实现了几个简单的操作。在Linux内核中链表的使用非常多，不过使用方法与本例完全不一样。后续有时间再详述。

ChainNode.c

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

#define MAX_DATA_LEN  128
#define CN_TRUE  0
#define CN_FALSE 1
#define CN_ERROR -1

typedef struct ChainNode ChainNode;

struct ChainNode {
	char data[MAX_DATA_LEN+1];
	ChainNode *next;
};

static int get_chain_len(ChainNode *head)
{
	int len = 0;
	ChainNode *node;

	node = head;
	while(node) {
		len++;
		node = node->next;
	}
	
	return len;
}

/*
 * Create a new node, and append it to the end of chain.
 */
static int chain_append(ChainNode *head, char *content, int content_len)
{
	ChainNode *node;
	ChainNode *new_node;

	if(NULL == head || NULL == content || content_len < 1 || content_len > MAX_DATA_LEN)
		return CN_ERROR;

	new_node = (ChainNode *)malloc(sizeof(ChainNode));
	if(NULL == new_node)
		return CN_ERROR;

	strncpy(new_node->data, content, content_len);
	new_node->next = NULL;

	node = head;
	while(node->next)
		node = node->next;
	
	node->next = new_node;
	
	return CN_TRUE;
}

/*
 * Destroy the chain except the head node
 */
static void chain_destroy(ChainNode *head)
{
	ChainNode *node;
	ChainNode *next;
	int i = 0;

	printf("There are %d nodes in chain.\n", get_chain_len(head));

	node = head;
	do {
		next = (node->next)->next;
		free(node->next);
		i++;
		node->next = next;
	} while(node->next);
	
	printf("Call free %d times.\n", i);
}

/*
 * index is start from 1. If index is valid, the data will be copy to ChainNode *target.
 */
static int chain_find_node_by_index(ChainNode *head, ChainNode *target, int index)
{
	ChainNode *node;

	if(NULL == head || NULL == target || index < 1 || index > get_chain_len(head))
		return CN_ERROR;

	node = head;
	while(--index > 0 && node) {
		node = node->next;
	}
	if(index != 0)
		return CN_ERROR;

	memcpy(target->data, node->data, MAX_DATA_LEN);

	return CN_TRUE;
}


static void chain_output(ChainNode *head)
{
	int i = 1;
	ChainNode *node;

	node = head;
	while(node) {
		printf("%d:%s\n", i++, node->data);
		node = node->next;
	}
}


int main()
{
	ChainNode head;
	ChainNode theThirdNode;
	char str1[] = "The second element";
	char str2[] = "The third element";
	char str3[] = "The fourth element";

	/* Create the head node */
	memset(&head, 0, sizeof(ChainNode));
	strcpy(head.data, "The first element");
	head.next = NULL;

	/* Append several elements */
	chain_append(&head, str1, strlen(str1));
	chain_append(&head, str2, strlen(str2));
	chain_append(&head, str3, strlen(str3));

	/* Output */
	chain_output(&head);	

	/* Find the element */
	memset(&theThirdNode, 0, sizeof(ChainNode));
	chain_find_node_by_index(&head, &theThirdNode, 3);	
	printf("Find 3:%s\n", theThirdNode.data);

	/* Destroy */
	chain_destroy(&head);

	return 0;
}