二级指针的三种内存模型 分类： C语言学习 2015-03-30 21:04 153人阅读 评论(0) 收藏

/*
Level tow point have three cache model
*/

#include <stdio.h>
#include <stdlib.h>
int Print(char**pArr);
int Print02(char**pArr,int num);
int GetMem(char***thirdModel,int len);
int Destory(char***thirdModel,int len);
int main()
{

	int i=0;
	char **thirdModel=NULL;
	//first cache model
	char *firstModel[10]={"abc","linux","unix",0};
	//second cache model
	char secondModel[3][10]={"abc","linux","unix"};
	//third cache model
	GetMem(&thirdModel,4);
	strcpy(*(thirdModel+0),"abc");		
	strcpy(*(thirdModel+1),"linux");		
	strcpy(*(thirdModel+2),"unix");		

	printf("firstModel start
");
	Print(firstModel);
	printf("secondModel start 
");
	Print02(secondModel,4);
	printf("thirdModel start
");
	Print(thirdModel);
	Destory(&thirdModel,4);
	return 0;		
}
int Print(char**pArr)
{
	int ret=0,i=0;
	if(NULL==pArr)
	{
		ret=-1;
		printf("arg is null error:%d
",ret);
		return ret;
	}
	while(*pArr)
	{
		printf("%s
",*pArr);	
		++pArr;
	}
	return ret;
}


int Print02(char**pArr,int num)
{
	int ret=0,i=0;
	//二级指针和指向数组的指针不一样。
	char(*arr)[10]=pArr;
	if(NULL==pArr)
	{
		ret=-1;
		printf("arg is null error:%d
",ret);
		return ret;
	}
	for(i=0;i<num;i++)
	{
		printf("%s
",*(arr+i));
	}
	return ret;
}

//三级指针做输出模型
int GetMem(char***thirdModel/*out*/,int len)
{
	int ret=0,i=0;
	if(NULL==thirdModel || len<=0)
	{
		ret=-1;
		return ret;
	}

	char**tmp=(char**)malloc(len*sizeof(char*));
	if(NULL==tmp)
	{
		ret=-1;
		return ret;
	}
	for(i=0;i<len-1;i++)
	{
		*(tmp+i)=(char*)malloc(100*sizeof(char));		
		if(NULL==*(tmp+i))
		{
			ret=-1;
			return ret;
		}
	}
	*(tmp+(len-1))=0;
	*thirdModel=tmp;
	return ret;
}
//销毁堆上的内存
int Destory(char***thirdModel,int len)
{
	int ret=0,i=0;
	char **tmp=NULL;
	if(NULL==thirdModel || len<=0)
	{
		ret=-1;
		return ret;
	}
	tmp=*thirdModel;
	for(i=0;i<len;i++)
	{
		if(NULL!=*(tmp+i))		
		{
			free(*(tmp+i));
			*(tmp+i)=NULL;
		}
	}
	free(tmp);
	*thirdModel=NULL;
	return ret;
}

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