C++CString 字串拷貝
class CString {
public:
int GetLength() const{
return strlen(m_pData);
}
CString(const char* p);
CString(const CString &str); //拷貝字串
CString(char ch,int nRepeat); //串內有N個ch字元
CString(const char* cstr,int nLenght); //根據字串常量取一部分字元
CString();
~CString();
friend CString operator+(const CString &str1,const CString &str2);
CString &operator=(const CString &str); //過載賦值符號只能在類成員區域;
CString &operator=(const char *str); //連== 賦值 ,立案等必須要有返回值,它就是用返回值去繼續賦值;
operator const char* (){return m_pData;}
friend std::ostream &operator<<(std::ostream &cout,CString &str);
friend bool operator!=(const CString& str1,const CString& str2);
friend bool operator!=(const char* str1,const CString& str2);
friend bool operator!=(const CString& str1,const char* str2);
friend bool operator==(const CString& str1,const CString& str2);
friend bool operator<(const CString& str1,const CString& str2);
friend bool operator>(const CString& str1,const CString& str2);
friend bool operator<=(const CString& str1,const CString& str2);
friend bool operator>=(const CString& str1,const CString& str2);
char operator[](int nIndex) const;
CString &operator+=(const CString& str);
private:
int a;
char* m_pData;
};
CString ---- CPP
#include "CString.hpp"
#include <iostream>
CString::CString(char ch,int nRepeat){
m_pData = new char[nRepeat+1];
memset(m_pData, ch, nRepeat);
m_pData[nRepeat] = '\0';
}
CString::CString(const char* cstr,int nLenght){
int nlen = strlen(cstr); //求出字串長度
if (nlen > nLenght)
nlen = nLenght;
m_pData = new char[nlen+1];
memcpy(m_pData, cstr,nlen);
m_pData[nlen] = '\0';
}
std::ostream &operator<<(std::ostream &out,CString &str){
//輸出的自定義輸出符號
out << str.m_pData;
return out;
}
CString operator+(const CString &str1,const CString &str2)
{
int n = str1.GetLength()+str2.GetLength();
CString str;
str.m_pData = new char[n+1]; // 這裡的意思是申請所需長度的位元組數然後在加一個0結束符位元組 所以表示為n+1 個位元組數；
strcpy(str.m_pData, str1.m_pData);
strcat(str.m_pData, str2.m_pData);
return str;
}
CString &CString::operator=(const CString &str){
int nLen = str.GetLength();
//首先判斷當前的字串長度是不是大於str字串的長度 如果說大於那就先delete在strcopy
//再重新建立一個更長的空間
if(GetLength() < nLen){
delete []m_pData;
m_pData = new char(nLen+1); //根據對方的長度重新申請一個空間
strcmp(m_pData, str.m_pData);
}
strcmp(m_pData, str.m_pData);
return *this;
}
CString::CString(const char* p){
//定一個變數記錄長度
int nLen = strlen(p);
m_pData = new char[nLen+1];
strcpy(m_pData, p);
}
CString::CString(const CString &str){
int nLen = str.GetLength();
//m_pData = str.m_pData; //淺拷貝這是屬於;
m_pData = new char[nLen+1]; //深拷貝
strcpy(m_pData, str.m_pData);
}
CString &CString::operator=(const char *str){
//首先獲取字串長度
int nLen = strlen(str);
//判斷字串長度是不是
if (nLen > GetLength()) {
//如果str字串長度大於GetLenght現有的字串長度的時候就刪除現有的字串重新分配空間
delete []m_pData;
m_pData = new char[nLen+1];
}
strcpy(m_pData, str);
return *this;
}
bool operator!=(const CString& str1,const CString& str2){
return strcmp(str1.m_pData, str2.m_pData) != 0;
}
bool operator!=(const char* str1,const CString& str2){
return strcmp(str1, str2.m_pData) !=0;
}
bool operator!=(const CString& str1,const char* str2){
return strcmp(str1.m_pData, str2) !=0;
}
bool operator==(const CString& str1,const CString& str2){
return strcmp(str1.m_pData, str2.m_pData) == 0;
}
bool operator<(const CString& str1,const CString& str2){
return strcmp(str1.m_pData, str2.m_pData) < 0;
}
bool operator>(const CString& str1,const CString& str2){
return strcmp(str1.m_pData, str2.m_pData) > 0;
}
bool operator<=(const CString& str1,const CString& str2){
return strcmp(str1.m_pData, str2.m_pData) <= 0;
}
bool operator>=(const CString& str1,const CString& str2){
return strcmp(str1.m_pData, str2.m_pData) >= 0;
}
char CString::operator[](int nIndex) const{
return m_pData[nIndex];
}
CString &CString::operator+=(const CString& str){
int nLen = GetLength()+str.GetLength();
char *p = new char[nLen+1];
strcpy(p,m_pData);
strcat(p, str.m_pData);
delete []m_pData; //刪除舊的空間
m_pData = p;
return *this;
}
CString::CString(){
m_pData = new char(0); //在堆空間上申請一個位元組
}
CString::~CString(){
//刪除堆空間
delete m_pData;
}
CPP ---- main
int main(int argc, const char * argv[]) {
CString s1 = "abc",s2 = "-xyz";
s1 += s2;
std::cout << s1 << std::endl;
return 0;
}
/*
int main(int argc, const char * argv[]) {
CString s4("All rights reserved",8); //截斷方式字串
CString s1 = "abc",s2 = "-xyz";
//CString s = s1+s2;
CString s = s1; //深拷貝
CString s3('*',8);
// s1 = s2; //直接賦值是屬於淺拷貝
CString s5;
s5 = s4 = "123456";
if (s1 == s4)
std::cout << "相等" << std::endl;
else
std::cout << "不相等" << std::endl;
if ("123456" != s4)
std::cout << "不等" << std::endl;
else
std::cout << "相等" << std::endl;
int i = 0;
while (i < s.GetLength()) {
printf("%c",s[i]);
++i;
}
std::cout << s1 << std::endl;
std::cout << s2 << std::endl;
std::cout << s << std::endl;
std::cout << s4 << std::endl;
printf("%d \n",s1.GetLength());
printf("%d \n",s2.GetLength());
std::cout << s.GetLength() << std::endl;
std::cout << s3 << std::endl;
std::cout << s4 << "\n" << s5 << std::endl;
//型別轉換字串
const char *p = s1; //C++字串與C語言字串;
return 0;
}
*/