2.6.1 流類和流對象

2.6.2 流的格式控制和錯誤處理

int ios::width();                    // 返回當前的寬度設置
int ios::width(int);                 // 設置寬度并返回上一次的設置
int ios::precision();                // 返回當前的精度設置
int ios::precision(int);             // 設置精度并返回上一次的設置
char ios::fill();                    // 返回當前空位填充的字符
char ios::fill(char);                // 設置空位填充的字符并返回上一次的設置
long ios::setf(long);                // 設置狀態標志并返回上一次的狀態標志
long ios::unsetf(long);              // 消除狀態標志并返回上一次的狀態標志
long ios::flags();                   // 返回當前的狀態標志
long ios::flags(long);              // 設置狀態標志并返回上一次的狀態標志

#include <iostream.h>
int  main()
{
    int nNum = 12345;
    double dNum = 12345.6789;
    char *str[] = {"This", "is", "a Test!"};
    cout.setf(ios::oct|ios::showbase|ios::showpos);
    // 設置標志：八進制，顯示基和正號
    cout<<nNum<<"\t"<<dNum<<endl;
    cout.setf(ios::hex|ios::scientific|ios::uppercase);
    // 設置十六進制，科學記數法和大寫標志
    cout<<nNum<<"\t"<<dNum<<endl;
    cout.fill('*');                    // 設置填充符號為*
    for (int i=0; i<3; i++)
    {
        cout.width(12);     cout<<str[i]<<"  ";
    }
    cout<<endl;
    cout.setf(ios::left);               // 設置標志：左對齊
    for (i=0; i<3; i++)
    {
        cout.width(12);     cout<<str[i]<<"  ";
    }
    cout<<endl;
    return 0;
}

#include <iostream.h>
#include <iomanip.h>
int  main()
{
     int nNum=12345;
    double dNum = 12345.6789;
    char *str[] = {"This", "is", "a Test!"};
    cout<<setiosflags(ios::oct|ios::showbase|ios::showpos);
     // 設置八進制，顯示基和正號
    cout<<nNum<<"\t"<<dNum<<endl;
    cout<<setiosflags(ios::hex|ios::scientific|ios::uppercase);
     // 設置十六進制，科學記數法和大寫標志
    cout<<nNum<<"\t"<<dNum<<endl;
    cout<<setfill('*');               // 設置填充符號為*
    for (int i=0; i<3; i++)
        cout<<setw(12)<<str[i]<<"  ";
    cout<<endl;
    cout<<setiosflags(ios::left);     // 設置標志：左對齊
    for (i=0; i<3; i++)
        cout<<setw(12)<<str[i]<<"  ";
    cout<<endl;
    return 0;
}

#include <iostream.h>
int  main()
{
    int i, s;
    char buf[80];
    cout<<"輸入一個整數：";
    cin>>i;
    s = cin.rdstate();
    cout<<"流狀態為："<<hex<<s<<endl;
    while (s)
    {
        cin.clear();
        cin.getline(buf, 80);
        cout<<"非法輸入，重新輸入一個整數：";
        cin>>i;
        s = cin.rdstate();
    }
    return 0;
}

2.6.3 使用輸入/輸出成員函數

#include <iostream.h>
int  main()
{
    char s1[80], s2[80], s3[80];
    cout<<"請輸入一個字符：";
    cout<<cin.get()<<endl;
    cin.get();                      // 提取換行符
    cout<<"請輸入一行字符串：";
    for (int i=0; i<80; i++)
    {
        cin.get(s1[i]);
        if (s1[i] == '\n')
        {
            s1[i] = '\0';
            break;                  // 退出for循環
        }
    }
    cout<<s1<<endl;
    cout<<"請輸入一行字符串：";
    cin.get(s2,80);
    cout<<s2<<endl;
    cin.get();                      // 提取換行符
    cout<<"請輸入一行字符串：";
    cin.getline(s3,80);
    cout<<s3<<endl;
    return 0;
}

#include <iostream.h>
int  main()
{
    char data[80];
    cout<<"請輸入："<<endl;
    cin.read(data, 80);
    data[cin.gcount()] = '\0';
    cout<<endl<<data<<endl;
    return 0;
}

2.6.4 提取和插入運算符重載

#include <iostream.h>
class CStudent
{
public:
     friend ostream&operator<<(ostream&os,CStudent&stu);
     friend istream&operator>>(istream&is,CStudent&stu);
private:
     char strName[10];                 // 姓名
     char strID[10];                   // 學號
     float fScore[3];                  // 三門成績
};
ostream& operator<< ( ostream& os, CStudent& stu )
{
     os<<endl<<"學生信息如下："<<endl;
     os<<"姓名："<<stu.strName<<endl;
     os<<"學號："<<stu.strID<<endl;
     os<<"成績："<<stu.fScore[0]<<",\t"<<stu.fScore[1]<<",\t"<<stu.fScore[2]<<endl;
     return os;
}
istream& operator>> ( istream& is, CStudent& stu )
{
     cout<<"請輸入學生信息"<<endl;
     cout<<"姓名：";         is>>stu.strName;
     cout<<"學號：";         is>>stu.strID;
     cout<<"三門成績：";     is>>stu.fScore[0]>>stu.fScore[1]>>stu.fScore[2];
     return is;
}
int  main()
{
     CStudent one;
     cin>>one;
     cout<<one;
     return 0;
}

2.6.5 文件流及其處理

#include <iostream.h>
#include<fstream.h>                  // 文件操作所必需的頭文件
int  main()
{
    fstream  file1;                  // 定義一個fstream類的對象用于讀
    file1.open("Ex_DataFile.txt", ios::in);
    if (!file1)
    {
        cout<<"Ex_DataFile.txt不能打開！\n";    return;
    }
    fstream  file2;                  // 定義一個fstream類的對象用于寫
    file2.open("Ex_DataFileBak.txt", ios::out | ios::trunc);
    if (!file2)
    {
        cout<<"Ex_DataFileBak.txt不能創建！\n"; file1.close();   return;
    }
    char ch;
    while (!file1.eof())
    {
        file1.read(&ch,1);   cout<<ch;     file2.write(&ch,1);
    }
    file2.close();                    // 不要忘記文件使用結束后要及時關閉
    file1.close();
    return 0;
}

#include <iostream.h>
#include <iomanip.h>
#include <fstream.h>
#include <string.h>
class CStudent
{
public:
    CStudent(char* name, char* id, float score = 0);
    void print();
    friend ostream& operator<< ( ostream& os, CStudent& stu );
    friend istream& operator>> ( istream& is, CStudent& stu );
private:
    char strName[10];                // 姓名
    char strID[10];                  // 學號
    float fScore;                    // 成績
};
CStudent::CStudent(char* name, char* id, float score)
{
    strncpy(strName,name,10);      strncpy(strID,id,10);      fScore=score;
}
void CStudent::print()
{
    cout<<endl<<"學生信息如下："<<endl;
    cout<<"姓名："<<strName<<endl;
    cout<<"學號："<<strID<<endl;
    cout<<"成績："<<fScore<<endl;
}
ostream& operator<< ( ostream& os, CStudent& stu )
{
    os.write(stu.strName,10);      os.write(stu.strID,10);    os.write((char*)&stu.fScore,4);
    return os;
}
istream& operator>> ( istream& is, CStudent& stu )
{
    char name[10];
    char id[10];
    is.read(name,10);              is.read(id,10);            is.read((char*)&stu.fScore,4);
    strncpy(stu.strName, name, 10);
    strncpy(stu.strID, id, 10);
    return is;
}
int  main()
{
    CStudent stu1("MaWenTao","99001",88);
    CStudent stu2("LiMing","99002",92);
    CStudent stu3("WangFang","99003",89);
    CStudent stu4("YangYang","99004",90);
    CStudent stu5("DingNing","99005",80);
    fstream file1;
    file1.open("student.dat",ios::out|ios::in|ios::binary);
    file1<<stu1<<stu2<<stu3<<stu4<<stu5;
    CStudent* one = new CStudent("","");
    const int size = sizeof(CStudent);
    file1.seekp(size*4);       file1>>*one;       one->print();
    file1.seekp(size*1);       file1>>*one;       one->print();
    file1.seekp(size*2, ios::cur);
    file1>>*one;       one->print();
    file1.close();
    delete one;
    return 0;
}