C语言-strlen/memcpy/strcpy

strlen不使用任何变量实现

int FunStrlen(const char *strDest)
{
	if(NULL == strDest)
	{
		printf("NULL == strDest, return!\n");
		return -1;
	}
	if('\0' == *strDest)
	{
		return 0;
	}
	else
	{
		return (1+FunStrlen(++strDest));
	}
}

	return *strDest ? 1+FunStrlen(++strDest) : 0;

	return ('\0' != *strDest) ? 1+FunStrlen(++strDest) : 0;

memcpy

void *FunMemcpy(void *dest, const void *src, size_t n)
{
	char *tmp=dest;
	const char *s=src;
	if(NULL==dest || NULL == src)
	{
		return;
	}

	while(n--)
	{
		*tmp++ = *s++;
	}
	return dest;
}

strcpy

char *FunStrcpy(char *dest, const char *src)
{
	char *tmp=dest;
	const char *s=src;
	if(NULL==dest || NULL == src)
	{
		return NULL;
	}

	while('\0' != *s)
	{
		*tmp++ = *s++;
	}
	return dest;
}