C语言基础 - 实现动态数组并增加内存管理

作者: gwk_iOS | 来源:发表于2016-12-15 00:46 被阅读548次

写在前面
弄了下个人站...防止内容再次被锁定...所有东西都在这里面
welcome~
个人博客

用C语言实现一个动态数组，并对外暴露出对数组的增、删、改、查函数
（可以存储任意类型的元素并实现内存管理）

这里我的编译器就是xcode

分析：
模拟存放一个 People类有2个属性字符串类型:姓名整型:年龄
array 结构体应当有数组长度:length 空间:capacity 存储对象:value(任意类型)
构造一个任意对象类.拥有retainCount属性.为内存计数器
使用一次retainCount+1,当retainCount为0时释放该对象指向的内存
贴出部分代码

//  Object.h
#ifndef Object_h
#define Object_h
#include <stdio>
//定义结构体
typedef struct Object{
    int retainCount;
}Object;
//宏定义方法 方便书写
#define OBJECTRETAIN(obj) objectRetain((Object*)obj)
#define OBJECTRELEASE(obj) objectRelease((Object*)obj)
#define GETRETAINCOUNT(obj) getRetainCount((Object*)obj)
void objectRetain(Object *obj);
void objectRelease(Object *obj);
int getRetainCount(Object *obj);
#endif /* Object_h */

//  Object.c
#include "Object.h"
#include <stdlib>
void objectRetain(Object *obj) {
 
    obj->retainCount ++;
//    printf("retain计数+1 = %d\n",obj->retainCount);

}

void objectRelease(Object *obj) {
    obj->retainCount --;
    if (obj->retainCount <= 0) {
        free(obj);
    }
//    printf("retain计数-1 = %d\n",obj->retainCount);

}
//获得当前计数
int getRetainCount(Object *obj) {
    return obj->retainCount;
}

下面开始封装.
首先是对原始数据的封装.

1. 将char* 字符串类型封装成String

//  String.h
#ifndef String_h
#define String_h
#include <stdio>
typedef struct String{
    int retainCount;
    char *value;
}String;
String* newString(char* value);
char* getStringValue(String* ins);
#endif /* String_h */

//  String.c
#include "String.h"
#include <stdlib>
#include "Object.h"

String* newString(char* value){
    String *str = malloc(sizeof(String));
    OBJECTRETAIN(str);
    str->value = value;
    return str;
    
}
char* getStringValue(String* ins){
    return ins->value;
}

2.将年龄的类型int封装成Interger

//  Integer.h

#ifndef Integer_h
#define Integer_h

#include <stdio>

typedef struct Integer{
    int retainCount;
    int value;

}Integer;

Integer* newInteger(int value);
int getIntegerValue(Integer* ins);
#endif /* Integer_h */

//  Integer.c

#include "Integer.h"
#include <stdlib>
#include "Object.h"

Integer *newInteger(int value) {
    Integer *new = malloc(sizeof(Integer));
    OBJECTRETAIN(new);
    new->value = value;
    return new;
}

int getIntegerValue(Integer* ins) {
    return ins->value;
}

3.定义数组中存放的类包含 name 和 age 属性

//  People.h

#ifndef People_h
#define People_h

#include <stdio>
#include "Integer.h"
#include "String.h"

typedef struct People{
    int retainCount;
    String* name;
    Integer* age;
    
}People;

People* newPeople(String *name,Integer *age);
String* getName(People* people);
Integer* getAge(People* people);
#endif /* People_h */

//  People.c

#include "People.h"
#include <stdlib>
#include "Object.h"

People* newPeople(String *name,Integer *age){
    People *newP = malloc(sizeof(People));
    OBJECTRETAIN(newP);
    newP->age = age;
    newP->name = name;
    return newP;
}
String* getName(People* people){
    return people->name;
}
Integer* getAge(People* people){
    return people->age;
}

4.准备工作都做完 ,下面我们来实现数组Array

//  Array.h

#ifndef Array_h
#define Array_h

#include <stdio>
#include "People.h"
#include "Object.h"
typedef Object* AnyObject;

typedef struct Array{
    int length;
    int capacity;
    AnyObject *value;
    
}Array;

Array* newArray();

//增加数组元素
void addElement(Array *array,AnyObject value);

//删除
Array* removeIndexAt(Array *arry,int index);

//插入
Array* insertIndexAt(Array *array,AnyObject value,int index);

//查找
AnyObject getValueIndexAt(Array *array,int index);

//获取数组长度
int getArrayLength(Array *array);

//销毁
void destroyArray(Array *array);

//打印
void printArray(Array *arr);


#endif /* Array_h */

//  Array.c

#include "Array.h"
#include <string>
#include <stdlib>
#include <assert>

//分配空间
static AnyObject* allocMemoryByCapacity(Array *arr){
    return malloc(sizeof(AnyObject) * arr->capacity);
}

//创建数组
Array* newArray(){
    Array *arr = malloc(sizeof(Array));
    arr->length = 0;
    arr->capacity = 32;
    arr->value = allocMemoryByCapacity(arr);
    return arr;
}

//获取数组长度
int getArrayLength(Array *array){
    return array->length;
}

//增加元素
void addElement(Array *array,AnyObject value){
    if (array->length >= array->capacity) {
        array->capacity *= 2;
        AnyObject *oldValue = array->value;
        memcpy(array->value, oldValue, array->length*sizeof(AnyObject));
        free(oldValue);
    }
    OBJECTRETAIN(value);
    array->value[array->length] = value;
    array->length++;
}

//删除元素
Array* removeIndexAt(Array *arry,int index){
    assert(index >= 0 && index < arry>length);  //断言 防止越界
    
    OBJECTRELEASE(getValueIndexAt(arry, index));
    
    arry->length -- ;
    for (int i = index-1; i < arry>length; i++) {
        arry->value[i] = arry->value[i+1];
    }
    return arry;
}

//在指定位置增加元素
Array* insertIndexAt(Array *array,AnyObject value,int index){
    if (array->length >= array->capacity) {
        array->capacity *= 2;
        AnyObject *oldValue = array->value;
        memcpy(array->value, oldValue, array->length*sizeof(AnyObject));
        free(oldValue);
    }
    array->length++;
    
    //插入指定位置
    array->value[index-1] = value;
    //将元素后移
    for (int i = index; i < array>length; i++) {
        array->value[array->length] = array->value[array->length-i];
    }
    OBJECTRETAIN(value);
    return array;
}



//获取某个元素
AnyObject getValueIndexAt(Array *array,int index){
    assert(index >= 0 && index < array>length);
    return array->value[index];
}

//销毁
void destroyArray(Array *array){
    free(array->value);
    free(array);
    printf("数组被销毁\n");
}
//打印结果
void printArray(Array *arr){
    for (int i = 0; i < arr>length; i++) {
        printf("位置:%d,姓名:%s,年龄:%d\n",i, getStringValue(getName((People*)getValueIndexAt(arr, i))),getIntegerValue(getAge((People*)getValueIndexAt(arr, i))));
    }
}

接下来就可以来测试数据了.

//  main.m

#import <Foundation>
#import "People.h"
#import "Array.h"
#import "Object.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        Array *arr = newArray();

        People *p0 = newPeople(newString("张三"), newInteger(20));
        People *p1 = newPeople(newString("李四"), newInteger(16));
        People *p2 = newPeople(newString("王五"), newInteger(17));
        People *p3 = newPeople(newString("赵二"), newInteger(14));
        People *p4 = newPeople(newString("林三"), newInteger(22));
        People *p5 = newPeople(newString("小明"), newInteger(18));
        People *p6 = newPeople(newString("小红"), newInteger(25));
        People *p7 = newPeople(newString("小方"), newInteger(11));
        People *p8 = newPeople(newString("小花"), newInteger(19));
        People *p9 = newPeople(newString("小兔"), newInteger(22));
        People *p10 = newPeople(newString("新人"), newInteger(23));
        
        
        
        //增加元素
        addElement(arr, (Object *)p0);
        addElement(arr, (Object *)p1);
        addElement(arr, (Object *)p2);
        addElement(arr, (Object *)p3);
        addElement(arr, (Object *)p4);
        addElement(arr, (Object *)p5);
        addElement(arr, (Object *)p6);
        addElement(arr, (Object *)p7);
        addElement(arr, (Object *)p8);
        addElement(arr, (Object *)p9);
        
        
        //释放内存
        OBJECTRELEASE((Object*) p0);
        OBJECTRELEASE((Object*) p1);
        OBJECTRELEASE((Object*) p2);
        OBJECTRELEASE((Object*) p3);
        OBJECTRELEASE((Object*) p4);
        OBJECTRELEASE((Object*) p5);
        OBJECTRELEASE((Object*) p6);
        OBJECTRELEASE((Object*) p7);
        OBJECTRELEASE((Object*) p8);
        OBJECTRELEASE((Object*) p9);
        

        printf("增加10个元素\n");
        printArray(arr);
        
        printf("删除第3个元素\n");
        //删除第数组中某一个元素
        removeIndexAt(arr, 3);
        printArray(arr);
        
        printf("插入P10成为第4个元素\n");
        //插入
        insertIndexAt(arr, (Object *)p10, 4);
        printArray(arr);
        
        OBJECTRELEASE((Object*) p10);

        printf("查找第5个元素\n");
        //index从0开始 查找第5个元素 index=4
        printf("位置:%d,姓名:%s,年龄:%d\n",4, getStringValue(getName((People*)getValueIndexAt(arr, 4))),getIntegerValue(getAge((People*)getValueIndexAt(arr, 4))));
     
        //销毁数组
        destroyArray(arr);
        
    }
    return 0;
}

看下结果吧。

array.png

有兴趣的可以研究下哈

网友评论

shyboy2012:不会内存泄露么数组内的指针指向的People对象没有手动去释放
gwk_iOS:@shyboy2012 恩多谢你说的这个和楼上几位都是一样的已经更改过了。
CDAKhx:为啥 allocMemoryByCapacity() 里 hard code 了 People？
CDAKhx:@gwk_ios 🏻
gwk_iOS:@桂一枫谢谢提醒，这里的数组对象是people所以当时写的时候就直接这样写了，应该是 return malloc(sizeof(AnyObject) * arr->capacity);
老司机Wicky:博主，想请教一下，当容量不够的时候capacity*2是什么考虑？而不是capacity+1。我理解的是不想频繁进行copy操作是么但是capacity量级较大的时候*2会不会造成内存得浪费
gwk_iOS:@老司机Wicky 是你说的这个情况，使用capacity是暂时分配的内存空间，确实没有考虑到量级大的层面。当然+1的话就太频繁了。感谢提醒。

本文标题：C语言基础 - 实现动态数组并增加内存管理

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C语言基础 - 实现动态数组并增加内存管理

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