strtok函数，实现memcpy还有memmove

先来讲一讲strtok函数：

int main()
{
	const char* p = "@.#";
	char arr[] = "zpengwei@yeah.net#hehe";
	char buf[50] = { 0 };// "zpengwei@yeah.net"
	strcpy(buf, arr);
	char* str = NULL;

for (str = strtok(buf, p); str != NULL; str=strtok(NULL, p))
{
		printf("%sn", str);
}//运用循环来实现

	char* str = strtok(buf, p);//zpengwei
	printf("%sn", str);
	str = strtok(NULL, p);//yeah
	printf("%sn", str);
	str = strtok(NULL, p);//net
	printf("%sn", str);
	strtok - 开始返回NULL
	return 0;
}

memcpy函数挺简单的，主要还是说一下memmove函数：

#include
#include
#include
#include
#include
void* my_memmove(void* dest,const void* str,size_t num)
{
	void* ret = dest;
	if (dest < str)//前->后
	{
		while (num--)
		{
			*(char*) dest = *(char*)str;
			dest = (char*)dest + 1;
			str = (char*)str + 1;
		}
	}
	else//后->前
	{
		dest = (char*)dest + num-1;
		str = (char*)str + num-1;
		while (num--)
		{
			*(char*)dest = *(char*)str;
			dest = (char*)dest - 1;
			str = (char*)str - 1;
		}
	}
	return ret;
}
void* my_memcpy(void* dest, const void* str, size_t num)
{
	void* ret = dest;
	assert(dest && str);
	while (num--)
	{
		*(char*)dest = *(char*)str;
		dest = (char*)dest + 1;
		str = (char*)str + 1;
	}
	return ret;
}
int main(void)
{
	int a[] = { 1,2,3,4,5,6,7,8,9,10 };
	int b[10] = { 0 };
	
	my_memcpy(b,a,5*sizeof(int));
	int i = 0;
	for (i = 0; i < 5; i++)
	{
		printf("%d ", b[i]);
	}
	return 0;
}