#include <iostream.h>
#include <iomanip.h>
#include <fstream.h>
#include <string.h>
class CStudentRec
{
public:
	CStudentRec(){chFlag = 'N';};		// 默認構造函數
	~CStudentRec(){};				// 默認析構函數
	friend	ostream& operator<< ( ostream& os, CStudentRec& stu );
	friend	istream& operator>> ( istream& is, CStudentRec& stu );
	CStudentRec& operator = (CStudentRec &stu)		// 賦值運算符重載
	{
		strncpy(strName, stu.strName, 20);
		strncpy(strID, stu.strID, 10);
		for (int i=0; i<3; i++)
			fScore[i] = stu.fScore[i];
		fAve = stu.fAve;
		chFlag = stu.chFlag;
		return *this;
	}
	char	chFlag;			// 標志,'A'表示正常，'N'表示空
	char	strName[20];		// 姓名
	char	strID[10];			// 學號
	float	fScore[3];			// 三門成績
	float	fAve;				// 總平均分
};
// CStudentRec類的實現
ostream& operator<< ( ostream& os, CStudentRec& stu )
{
	os.write(&stu.chFlag, sizeof(char));
	os.write(stu.strName, sizeof(stu.strName));
	os.write(stu.strID, sizeof(stu.strID));
	os.write((char *)stu.fScore, sizeof(float)*3);
	os.write((char *)&stu.fAve, sizeof(float));
	return os;
}
istream& operator>> ( istream& is, CStudentRec& stu )
{
	char name[20],id[10];
	is.read(&stu.chFlag, sizeof(char));
	is.read(name, sizeof(name));
	is.read(id, sizeof(id));
	is.read((char*)stu.fScore, sizeof(float)*3);
	is.read((char*)&stu.fAve, sizeof(float));
	strncpy(stu.strName, name, sizeof(name));
	strncpy(stu.strID, id, sizeof(id));
	return is;
}

class CStudentFile
{
public:
	CStudentFile(char* filename);
	~CStudentFile();
	void	Add(CStudentRec stu);			// 添加記錄
	void	Delete(char* id);				// 刪除學號為id的記錄
	void	Update(int nRec, CStudentRec stu);	// 更新記錄號為nRec的內容，nRec從0開始 
	int	Seek(char* id, CStudentRec &stu);	// 按學號查找, 返回記錄號，-1表示沒有找到 
	int	GetRecCount(void);				// 獲取文件中的記錄數
	int	GetStuRec( CStudentRec* data );	// 獲取所有記錄,返回記錄數
private:
	char*	strFileName;				// 文件名
};
// CStudentFile類的實現
CStudentFile::CStudentFile(char* filename)
{
	strFileName = new char[strlen(filename)+1];
	strcpy(strFileName, filename);
}
CStudentFile::~CStudentFile()
{
	if (strFileName) delete []strFileName;
}
void CStudentFile::Add(CStudentRec stu)	
{
	// 打開文件用于添加	
	fstream file(strFileName, ios::out|ios::app|ios::binary );
	file<<stu;
	file.close();
}
void CStudentFile::Delete(char *id)
{
	CStudentRec temp;
	int nDel = Seek(id, temp); 
	if (nDel<0) return;
	// 設置記錄中的chFlag為'N'
	temp.chFlag = 'N';
	Update( nDel, temp );
}
void CStudentFile::Update(int nRec, CStudentRec stu)
{
	fstream file(strFileName, ios::in|ios::out|ios::binary);	// 二進制讀寫方式
	if (!file) {
		cout<<"the "<<strFileName<<" file can't open !\n";
		return ; 
	}
	int nSize = sizeof(CStudentRec) - 1;
	file.seekg( nRec * nSize);	
	file<<stu;
	file.close();
}
int CStudentFile::Seek(char* id, CStudentRec& stu)	// 按學號查找 
{
	int nRec = -1;
	fstream file(strFileName, ios::in|ios::nocreate);	// 打開文件用于只讀
	if (!file) {
		cout<<"the "<<strFileName<<" file can't open !\n";
		return nRec; 
	}
	int i=0;
	while (!file.eof())	{
		file>>stu;
		if ((strcmp(id, stu.strID) == 0) && (stu.chFlag == 'A')){
			nRec = i;	break;
		}
		i++;
	}
	file.close();
	return nRec;	
}
int	CStudentFile::GetRecCount(void)
{
	fstream file(strFileName, ios::in|ios::nocreate);	// 打開文件用于只讀
	if (!file) {
		cout<<"the "<<strFileName<<" file can't open !\n";
		return 0; 
	}
	int nRec = 0;
	while (!file.eof()) {	// 讀出所有記錄
		CStudentRec data;
		file>>data;		
		if (data.chFlag == 'A')	nRec++;
	}
	file.close();
	return nRec;
}
int CStudentFile::GetStuRec( CStudentRec* data)
{
	fstream file(strFileName, ios::in|ios::nocreate);	// 打開文件用于只讀
	if (!file) {
		cout<<"the "<<strFileName<<" file can't open !\n";
		return 0; 
	}
	int nRec = 0;
	while (!file.eof()) {	// 讀出所有記錄
		CStudentRec stu;
		file>>stu;		
		if (stu.chFlag == 'A') {
			data[nRec] = stu;
			nRec++;	
		}
	}
	file.close();
	return nRec;
}