C and Pointers (continued)

Objective

The previous "C" and "pointers" may be about C and pointers to some of the content does not say through, down to write a list of the implementation, of course, but also with C function pointers to simulate OO structure to do. The list structure itself is more complex (regarding the use of pointers), so this example may be clearer. The reason for choosing the list is that you must have contacted this simple data structure at school, and it may be easier to understand it from a more familiar example.

Interface definition

You can first look at the definition of the interface, similar to Java or C #:

/*
　*　File:　　　IList.h
　*　Author:　juntao.qiu
　*
　*　Created　on　May　22,　2009,　2:51　PM
　*/　

#ifndef　_ILIST_H
#define　　　　_ILIST_H　

typedef　struct　node{
　　　　void　*data;
　　　　struct　node　*next;
}Node;　//定义List中的元素类型，void * 相当于C中的泛型，可以支持任何结构的节点

typedef　struct　list{
　　　　struct　list　*_this;
　　　　Node　*head;
　　　　int　size;
　　　　void　(*insert)(void　*node);
　　　　void　(*drop)(void　*node);
　　　　void　(*clear)();
　　　　int　(*getSize)();
　　　　void*　(*get)(int　index);
　　　　void　(*print)();
}List;　//用head (Node)来维护链表的链!

void　insert(void　*node);
void　drop(void　*node);
void　clear();
int　getSize();
void*　get(int　index);
void　print();

#endif　　　　/*　_ILIST_H　*/

Interface to define all the exposed methods, as with all the list structures, we define the

void insert(node);//插入一个新的节点到List
void drop(node);//删除一个指定的节点
void clear();//清空List
int getSize();//取到List的大小
void* get(int index);//取到指定位置的元素
void print();//打印整个List,用于调试

Such a few methods.

Implementation of the interface

Then look at the implementation, as in the previous article, introduce a _this pointer to the tag list itself, and modify the state in the real object by referencing the pointer.

#include <stdlib.h>
#include "IList.h"

Node *node = NULL;
List *list = NULL;

/* Function declaration block, the function is already explained on the top.
void insert (void *node);
void drop (void *node);
void Clear ();
int GetSize ();
void print ();
void* get (int index);

/* Construction Method * *
List *listconstruction () {
List = (list*) malloc (sizeof (list));
node = (node*) malloc (sizeof (node));
list->head = node;
List->insert = insert;
List->drop = drop;
List->clear = clear;
list->size = 0;
List->getsize = GetSize;
List->get = get;
List->print = print;
List->_this = list;

Return (list*) List;
}

void Listdeconstruction () {
}

Insert node, size increased by 1
void insert (void *node) {
Node *current = (node*) malloc (sizeof (node));
current->data = node;
Current->next = list->_this->head->next;
List->_this->head->next = current;
(list->_this->size) + +;
}

Delete a node, size minus 1
void drop (void *node) {
Node *t = list->_this->head;
Node *d = NULL;
int i = 0;
For (I;i < list->_this->size;i++) {
D = list->_this->head->next;
if (D->data = = ((node*) Node)->data) {
List->_this->head->next = d->next;
Free (d);
(list->_this->size)--;
Break
}else{
List->_this->head = list->_this->head->next;
}
}
List->_this->head = t;
}

Take to the node of the specified index
void* get (int index) {
Node *node = list->_this->head;
int i = 0;

if (Index > List->_this->size) {
return NULL;
}else{
For (I;i < index;i++) {
node = node->next;
}
if (node!= (node*) 0) {
Return node->data;
}else{
return NULL;
}
}
}

void Clear () {
Node *node = NULL;
int i = 0;
for (i;i< list->_this->size;i++) {
node = list->_this->head;
List->_this->head = list->_this->head->next;
Free (node);
}
list->_this->size = 0;
list = NULL;
}

int GetSize () {
Return list->_this->size;
}

For debugging purposes, like this getsize (), print (), you need to be aware that you cannot make any changes to the original pointer during the call.
Otherwise, unpredictable errors may occur.
void print () {
Node *node = list->_this->head;
int i = 0;
For (i;i <= list->_this->size;i++) {
if (node!= (node*) 0) {
printf ("[%p] = {%s}\n", &node->data, Node->data);
node = node->next;
}
}
}