String的寫(xiě)時(shí)拷貝

//test.h #pragma once#include <iostream> #include <string.h> #include <cstdio> #include <assert.h> using namespace std;#define TESTHEADER printf("\n================%s=============\n", __FUNCTION__) class String { public:String(const char* str);String(const String& s);String& operator = (const String s);~String();char* c_str();void CopyOnWrite();char& operator [] (size_t pos);const char& operator [] (size_t pos)const;String& Insert(size_t pos, char ch);String& Insert(size_t pos, const char* str);String& Append(const char* str);String& Erase(size_t pos, size_t n);void Expand(size_t n); private:char* _str;int* _pcount;size_t _size;size_t _capacity; };//test.cc #include "test.h" String::String(const char* str):_size(strlen(str)) ,_capacity(_size) {_str = new char [strlen(str) + 1];_pcount = new int(1);strcpy(_str, str); }//s(s1) String::String(const String& s) {_str = s._str;_pcount = s._pcount;++(*_pcount);_size = s._size;_capacity = s._capacity; }//s1 = s2 String& String:: operator = (const String s) {if(_str != s._str){_str = s._str;--(*_pcount);if(*_pcount == 0){delete [] _str;delete _pcount;}_size = s._size;_capacity = s._capacity;}return *this; }String::~String() {delete [] _str;delete _pcount;_size = 0;_capacity = 0; } char* String::c_str() {return _str; }void String::CopyOnWrite() {if(*_pcount > 1){char* tmp = new char[_size + 1];strcpy(tmp, _str);--(*_pcount);_str = tmp;_pcount = new int(1);} }//s[1] char& String::operator [] (size_t pos) {CopyOnWrite();return _str[pos]; }const char& String:: operator [] (size_t pos)const {return _str[pos]; }void String::Expand(size_t n) {if( *_pcount == 1){char* tmp = new char [n];strcpy(tmp, _str);delete [] _str;--(*_pcount);delete _pcount;_pcount = new int(1);_str = tmp;}else{char* tmp = new char [n];strcpy(tmp, _str);_str = tmp;--(*_pcount);_pcount = new int(1);} }String& String::Insert(size_t pos, char ch) {assert(pos < _size);if(_size == _capacity){Expand(2 * _capacity);}int end = _size;for(; end >= (int)pos; end--){_str[end] = _str[end - 1];}_str[pos] = ch;return *this; }String& String::Insert(size_t pos, const char* str) {assert(pos <= _size);int len = strlen(str);if(_size == _capacity){Expand(_size + len);}int end = _size;for(; end >= (int)pos; end--){_str[end + len] = _str[end];}strncpy(_str + pos, str, len);_size += len;/* _str[_size] = '\0'; */return *this; }String& String::Append(const char* str) {int len_ = strlen(_str);int len = strlen(str);if(_size == _capacity){Expand(_size + len);}strcpy(_str + len_, str);_size += len;return *this; }String& String::Erase(size_t pos, size_t n) {assert(pos <= _size);CopyOnWrite();if(pos + _size > _capacity){_str[pos] = '\0';}strcpy(_str + pos, _str + pos + n);_size -= n;return *this; }

如果有什么錯(cuò)誤,還望大家提出來(lái),共同進(jìn)步

總結(jié)

以上是生活随笔為你收集整理的C++:String的写时拷贝的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。