重载操作符new / allocate大于对象大小

我试图重载我的类的operator new，我想为对象的属性和在类中未定义的字符向量分配空间。

但是当我实例化一个新对象时，前一个对象的字符正在改变。我做错了什么吗?

class StringData
{       
public:
    friend class String;
    int refCount;
    int len;
    int maxLen;
    ~StringData()
    {
    }
    StringData()
    {
        maxLen = 1000;
        len = 0;
        refCount = 1;
    }
    StringData(const char * string)
    {
        maxLen = 1000;
        char * data = buffer();
        len = 0;
        while (string[len] != '' && len < (maxLen - 1))
        {
            data[len] = string[len];
            len++;
        }
        data[len] = '';
        refCount = 1;
    }
    char* buffer()
    {
        return reinterpret_cast<char*>(this + 12);
    }
public:
    void* operator new(size_t size, int maxLen)
    {
        return ::operator new(size + round4(maxLen + 1));
    }
    static int round4(int len)
    {
        return ((((int) (len / 4)) + 1) * 4);
    }
    void operator delete(void* obj)
    {
        ::operator delete(obj); 
    }
    void operator delete(void* obj, int size) throw ()
    {
        ::operator delete(obj); 
    }
};

我在其他类中使用:

class String{
public:
    StringData * data;
    String(StringData * data){
        this->data = data;
    }
public:
    String(const char*);
    String(const String&);
    ~String();
    String& operator =(const String);
    String& operator =(const char *);
    int length() const;
    bool operator ==(const String&) const;
    int compare(const String&) const;
    bool operator ==(const char*) const;
    int compare(const char*) const;
    String& operator +(const String&) const;
    String operator +(const char*) const;
    String operator +=(const String&);
    String operator +=(const char*);
    String toLower();
    String toUpper();
    char operator [ ](int) const;
    char& operator [ ](int);
    void print() const;

};

String::String(const char * string){
int stringLen = 0;
while (string[stringLen] != '')
    stringLen++;
data = new (stringLen + 1) StringData(string);

}

String::String(const String& string){
data = string.data;
string.data->refCount++;

}

String::~String(){
this->data->refCount--;
if (this->data->refCount == 0)
    delete data;

}

String& String::operator=(const String string){
data->refCount--;
if (this->data->refCount == 0)
    delete data;
data = string.data;
string.data->refCount++;
return *this;

}

void String::print() const{ printf("%sn", data->buffer()); }

我的主要功能是:

int main(){
String *a = new String("boisahzashdacaraverdeepretaeazuleamarelaecinzaevermelha");
a->print();
String * s = new String("freestepehnoisquevoaashashashhasshashhasssasassadasd");
String * b = new String("kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk");
a->print();
s->print();
return 0;

}

当我执行时，字符串被打破了:

boisahzashdacaraverdeepretaeazuleamarelaecinzaevermelha

boisahzashdacaraverd

freestepehnoisquevoa