string自我实现

#define _CRT_SECURE_NO_WARNINGS#includestring.hnamespace fhj{//string::string()//先对函数进行初始化//:_str(new char[1] {\0})//这里要是直接为空那么要是访问的话就算是空指针解引用了会直接报错所以这里面放一个\0//, _size(0)//这两个都不算\0//, _capacity(0)//{ }string::string(const char* str)//如果定义的时候传入了数据则就需要调用这个//:_str(new char[strlen(str)1])//要是直接拷贝的话原来的的const但是现在没有const这是权限放大所以先开辟空间后续在进行复制:_size(strlen(str))// 这里用三个strlen过于浪费可以进行修改//,_capacity(_size)//修改后这样但是C底层在初始化列表进行初始化的时候是根据同文件里面的顺序这样好像也不可以//,_str(new char[_size1]){_capacity_size;_strnew char[_size 1];//这里可以不直接使用初始化列表直接在函数体内进行赋值strcpy(_str, str);}string::string(const string s){_str new char[s._capacity 1];memcpy(_str, s._str, s._size 1);_size s._size;_capacity s._capacity;}string::~string(){delete[]_str;_str nullptr;_size _capacity 0;}void string::swap(string s){std::swap(_str, s._str);std::swap(_size, s._size);std::swap(_capacity, s._capacity);}string::iterator string::begin(){return _str;}string::iterator string::end(){return _str _size;}string::const_iterator string::begin() const{return _str;}string::const_iterator string::end() const{return _str _size;//end返回的位置都是\0}size_t string::size() const{return _size;}char string::operator[](size_t i){assert(i _size);return _str[i];}const char string::operator[](size_t i) const{assert(i _size);return _str[i];}const char* string::c_str() const//函数这个该函数的目的就是直接返回str{return _str;}void string::reserve(size_t n){if (n _capacity){char* str new char[n 1];//多留一个空用来存\0//strcpy(str, _str);//如果_str里面中间有\0,那么这里的拷贝就会出现错误memcpy(str, _str, _size 1);//那我们就用memcpy这样就可以指定长度就不需要担心中间有\0导致出现问题了delete[] _str;//此处只是释放了这里面的内容但是空间还在_str str;//原来是空间不够但是现在里面没用东西在进行复制的话空间不够编译器会自己想办法_capacity n;}}void string::push_buck(char ch){if (_size _capacity){size_t newcapacity _capacity 0 ? 4 : 2 * _capacity;reserve(newcapacity);_capacity newcapacity;}_str[_size] ch;_size;_str[_size] \0;}void string::appead(const char* str){size_t len strlen(str);if (_size len _capacity){size_t newcapacity 2 * _capacity _size len ? 2 * _capacity : _size len;reserve(newcapacity);_capacity newcapacity;}//strcpy(_str _size, str);//和上面比较这里就可以使用strcpy因为传入的是const类型的里面不可能存在\0memcpy(_str _size, str, len1);_size len;}string string::operator(char ch){push_buck(ch);return *this;}string string::operator(const char* str){appead(str);return *this;}std::ostream operator(std::ostream end, const string s){//end s.c_str();//此时就会遇见一个问题当进行尾部插入的时候\0之后后面的在插入任何东西都不可能在输出了for (size_t i 0; i s.size();i){end s[i];}return end;}void string::insert(size_t pos, char ch){assert(pos _size);if (_size _capacity){size_t newcapacity _capacity 0 ? 4 : 2 * _capacity;reserve(newcapacity);_capacity newcapacity;}//int end _size;//这里由无符号变成有符号的为了就是保证头插顺利//while (end (int)pos)//{//_str[end 1] _str[end];///end--;//}size_t end _size 1;//这样写就可以不用搞强转那些东西了while (end pos){_str[end] _str[end - 1];end--;}_str[pos] ch;_size;}void string::insert(size_t pos, const char* str){assert(pos _size);size_t len strlen(str);if (_size len _capacity){size_t newcapacity 2 * _capacity _size len ? 2 * _capacity : _size len;reserve(newcapacity);_capacity newcapacity;}//size_t end _size;//while (end (int) pos)//{// _str[end len] _str[end];// end--;//}size_t end _size len;while (end pos len - 1){_str[end] _str[end-len];end--;}//先预留位置for (size_t i 0; i len; i){_str[pos i] str[i];}//在进行填充_size len;}const size_t string::npos -1;void string::erase(size_t pos, size_t len){//如果要把pos后面的值全部删除这个就比交简单啦assert(pos _size);if (len npos || len (pos - _size)){_str[pos] \0;_size pos;}else{size_t i pos len;memmove(_str pos, _str i, _size - i 1);_size - len;}}size_t string::find(char ch, size_t pos) const{assert(pos _size);for (size_t i pos; i _size; i){if (_str[i] ch){return i;}}return npos;}size_t string::find(const char* str, size_t pos) const{const char* p1 strstr(_str pos, str);if (p1 nullptr){return npos;}else{return p1-_str;}}string string::substr(size_t pos, size_t len){if (len npos || len _size - pos){len _size - pos;}string str;str.reserve(len);for (int i 0; i len; i){str _str[i pos];}return str;}bool string::operator(const string s) const{size_t i1 0, i2 0;while (i1 _size i2 s._size){if (_str[i1] s[i2]){return true;}else if (_str[i1]s[i2]){return false;}else {i1;i2;}}return i2 s._size;}bool string::operator(const string s)const{size_t i1 0, i2 0;while (i1 _size i2 s._size){if (_str[i1] ! s._str[i2]){return false;}else {i1;i2;}return i1 _size i2 s._size;}}bool string::operator(const string s)const{return !(*this s);}bool string::operator(const string s)const{return *this s *this s;}bool string::operator(const string s)const{return *this s *this s;}void string::clear(){_str[0] \0;_size 0;}std::istream operator(std::istream in, string s){s.clear();//char buff[128];int i 0;char ch in.get();while (ch ! ch ! \n){buff[i] ch;if (i 127){buff[i] \0;s buff;i 0;}ch in.get();}if (i 0){buff[i] \0;s buff;}return in;}std::istream getline(std::istream in, string s, char delim){s.clear();char buff[128];int i 0;char ch in.get();while (ch ! delim){buff[i] ch;if (i 127){buff[i] \0;s buff;i 0;}ch in.get();}if (i 0){buff[i] \0;s buff;}return in;}void swap(string x, string y){x.swap(y);}}