3.8cstring.cpp

CString 是一种很有用的数据类型。 这里面的好多函数都是自己写的

#include<iostream.h>
//#include<string.h>
class CString
{
public:
	CString(int n=1);
	CString(char *s);
	CString(const CString &s);
	CString &operator=(const CString &s);
	~CString();
	CString operator+(const CString &sa);
	CString operator+(const char *s);//s3=s1+"ddd";
	friend CString operator+(const char *s,const CString &sa);
	friend ostream & operator<<(ostream &out,const CString &s);

private:
	char *str;

	int strlen(const char *s);
	char *strcpy(char *strDest, const char *strSrc); 
	char *strcat(char *strDest, const char *strSrc);

	
};

int CString::strlen(const char *s)
{
	int num=0;
	if(s == NULL)
	{
		return num;
	}
	while( *s++ != '\0')// yhp\0
	{
		num++;
	}
	return num;
}

char * CString::strcat(char *strDest, const char *strSrc)
{
	char * ret=strDest;
	strDest+=strlen(strDest);
	while((*strDest++ = *strSrc++) != '\0');
	return ret;
}

char * CString::strcpy(char *strDest, const char *strSrc)
{
	char *ret=strDest;
	while((*strDest++ = *strSrc++) != '\0');
	return ret;
	/*
	//char *ret=strDest;
	int i=0;
	for(i=0;strSrc[i] != '\0';i++)
	{
		strDest[i]=strSrc[i];
	}
	return strDest;
	*/
}


CString::CString(int n)
{
	if(n>1)
	{
		str=new char[n];
		str[0]='\0';

	}
	else
	{
		str=new char[1];
		str[0]='\0';
	}
}

CString::CString(char *s)
{
	if(s!=NULL)
	{
		str=new char[strlen(s)+1];
		strcpy(str,s);
	}
	else
	{
		str=new char[1];
		str[0]='\0';
	}
}
CString::CString(const CString &s)
{
	if(strlen(s.str)>1)
	{
		str=new char[strlen(s.str)+1];
		strcpy(str,s.str);
	}
	else
	{
		str=new char[1];
		str[0]='\0';
	}

}

CString & CString::operator=(const CString &s)
{
	if(this == &s)
		return *this;
	delete []str;// str=0;
	str=new char[strlen(s.str)+1];
	strcpy(str,s.str);
	return *this;	
}//s1.operator=(s2);


CString::~CString()
{
	if(str != NULL)
	{
		delete []str;
	}
	str=NULL;
}

CString CString::operator+(const CString &sa)
{
	char *s=new char[strlen(this->str)+strlen(sa.str)+1];
	strcpy(s,this->str);
	strcat(s,sa.str);
	return CString(s);
}
void main()
{
	CString s1;
	CString s2("ym");
	CString s3;
	s3=s1+s2;
	s3=s1+"dddddd";
	s3="ddddd"+s1;// operator+("ddddd",s1);
}

/*	//char *p="yhphm";//*(p+0)
//	cout<<(void *)p<<endl;//cout<<*p<<endl; cout<<p[0]<<endl;
	char p[]={"yhphm"};
	cout<<p<<endl;
	cout<<*p<<endl;
	cout<<&p<<endl;
	cout<<(void *)p<<endl;
	*/