memcpy用指针的实现通过判断地址是否重合解决掉字符串结束符('\0')问题

标签：c 语言 算法   c语言   指针   字符串的操作   

#include<stdlib.h>
#include<stdio.h>
#include<string.h>
//memcpy的实现
int Mymem(char *dest, char *src, int size)
{
	if (dest == NULL || src == NULL || size == 0)
	{
		return -1;
	}

	char *d = NULL;
	char *s = NULL;
	d = dest;
	s = src;
	//if ((unsigned char*)dst <= (unsigned char*)src|| (unsigned char *)dst >= ((unsigned char *)src + count))
	//判断地址事是否重合
	if (d > s && d < s+size)
	{
		d = dest + size;
		s = src + size;
		while (size--)
		{
			*d = *s;
			d--;
			s--;
		}
	}
	//不重合的情况直接将内存进行拷贝
	else
	{
		while (size-- && *s != '\0')
		{
			*d++ = *s++;
		}
	}
	return 0;
}

void main()
{
	//地址重合的情况
	char p1[10] = "abcdef";
	Mymem(p1 + 2, p1, strlen(p1));
	printf("p1 = %s\n", p1);
	printf("p2 = %s\n", p1 + 2);


	//地址不重合的情况
	char p3[10] = "abcdef";
	char p4[100] = {0};
	Mymem(p4, p3, strlen(p1));
	printf("p3 = %s\n", p3);
	printf("p4 = %s\n", p4);
	system("pause");
}

memcpy用指针的实现通过判断地址是否重合解决掉字符串结束符('\0')问题,布布扣,bubuko.com

memcpy用指针的实现通过判断地址是否重合解决掉字符串结束符('\0')问题

标签：c 语言 算法   c语言   指针   字符串的操作   

原文地址：http://blog.csdn.net/han1558249222/article/details/25906689