用C++实现一个简易的golang 的Slice

struct Slice
{
	SharedStr* sharedStr;
	int p;
	int length;
	virtual ~Slice()
	{
		sharedStr->free();
	}
	Slice():Slice("") {

	}
	Slice(const Slice& right) : p(right.p),length(right.length)
	{
		right.sharedStr->copy(&sharedStr);
	}
	Slice& operator=(const Slice& right)  {
		right.sharedStr->copy(&sharedStr);
		p = right.p;
		length = right.length;
		return *this;
	}
	Slice(string&& data):p(0)
	{
		length = data.length();
		sharedStr = new SharedStr(move(data));
	}
	Slice(Slice* parent, int start, int end)
	{
		parent->sharedStr->copy(&sharedStr);
		p = parent->p + start;
		length = end - start;
	}
	Slice(int len, int cap) : length(len),p(0)
	{
		if (!cap)cap = len;
		sharedStr = new SharedStr(cap);
	}
	size_t cap() {
		return sharedStr->capacity() - p;
	}
	Slice operator()(int start, int end)
	{
		return Slice(this, start, end);
	}
	unsigned char operator[](int i)
	{
		return ((unsigned char*)(*sharedStr))[p+i];
	}
	Slice operator+(const Slice& right) {
		return append((void*)right.point(), right.length);
	}
	const char* point() const{
		return sharedStr->data.data() + p;
	}
	Slice append(void * data ,int len) {
		if (len > cap() - length) {
			string newStr;
			newStr.resize(p + length + len);
			memcpy((void*)newStr.data(), sharedStr->data.data(), p + length);
			memcpy((void*)(newStr.data() + p + length), data, len);
			return Slice(move(newStr));
		}
		memcpy((void*)(point() + length), data, len);
		return Slice(this, 0, length + len);
	}
	OPERATOR_CHARS((*sharedStr)+p)
};

struct SharedStr
{
    string data;
    int refCount;
	SharedStr(size_t size):refCount(1) {
		data.reserve(size);
	}
    SharedStr(string &&right) : data(move(right)),refCount(1)
    {
    }
    
    void free()
    {
        refCount--;
        if (refCount == 0)
        {
            delete this;
        }
    }
	void copy(SharedStr** target) {
		*target = this;
		refCount++;
	}
	void expend(size_t t) {
		data.resize(data.capacity() + t);
	}
	size_t capacity() {
		return data.capacity();
	}
	OPERATOR_CHARS(data.data())
};