2.6.1 流类和流对象

2.6.2 流的格式控制和错误处理

int ios::width();                    // 返回当前的宽度设置
int ios::width(int);                 // 设置宽度并返回上一次的设置
int ios::precision();                // 返回当前的精度设置
int ios::precision(int);             // 设置精度并返回上一次的设置
char ios::fill();                    // 返回当前空位填充的字符
char ios::fill(char);                // 设置空位填充的字符并返回上一次的设置
long ios::setf(long);                // 设置状态标志并返回上一次的状态标志
long ios::unsetf(long);              // 消除状态标志并返回上一次的状态标志
long ios::flags();                   // 返回当前的状态标志
long ios::flags(long);              // 设置状态标志并返回上一次的状态标志

#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);
    // 设置标志：八进制，显示基和正号
    cout<<nNum<<"\t"<<dNum<<endl;
    cout.setf(ios::hex|ios::scientific|ios::uppercase);
    // 设置十六进制，科学记数法和大写标志
    cout<<nNum<<"\t"<<dNum<<endl;
    cout.fill('*');                    // 设置填充符号为*
    for (int i=0; i<3; i++)
    {
        cout.width(12);     cout<<str[i]<<"  ";
    }
    cout<<endl;
    cout.setf(ios::left);               // 设置标志：左对齐
    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);
     // 设置八进制，显示基和正号
    cout<<nNum<<"\t"<<dNum<<endl;
    cout<<setiosflags(ios::hex|ios::scientific|ios::uppercase);
     // 设置十六进制，科学记数法和大写标志
    cout<<nNum<<"\t"<<dNum<<endl;
    cout<<setfill('*');               // 设置填充符号为*
    for (int i=0; i<3; i++)
        cout<<setw(12)<<str[i]<<"  ";
    cout<<endl;
    cout<<setiosflags(ios::left);     // 设置标志：左对齐
    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<<"输入一个整数：";
    cin>>i;
    s = cin.rdstate();
    cout<<"流状态为："<<hex<<s<<endl;
    while (s)
    {
        cin.clear();
        cin.getline(buf, 80);
        cout<<"非法输入，重新输入一个整数：";
        cin>>i;
        s = cin.rdstate();
    }
    return 0;
}

2.6.3 使用输入/输出成员函数

#include <iostream.h>
int  main()
{
    char s1[80], s2[80], s3[80];
    cout<<"请输入一个字符：";
    cout<<cin.get()<<endl;
    cin.get();                      // 提取换行符
    cout<<"请输入一行字符串：";
    for (int i=0; i<80; i++)
    {
        cin.get(s1[i]);
        if (s1[i] == '\n')
        {
            s1[i] = '\0';
            break;                  // 退出for循环
        }
    }
    cout<<s1<<endl;
    cout<<"请输入一行字符串：";
    cin.get(s2,80);
    cout<<s2<<endl;
    cin.get();                      // 提取换行符
    cout<<"请输入一行字符串：";
    cin.getline(s3,80);
    cout<<s3<<endl;
    return 0;
}

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

2.6.4 提取和插入运算符重载

#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];                   // 学号
     float fScore[3];                  // 三门成绩
};
ostream& operator<< ( ostream& os, CStudent& stu )
{
     os<<endl<<"学生信息如下："<<endl;
     os<<"姓名："<<stu.strName<<endl;
     os<<"学号："<<stu.strID<<endl;
     os<<"成绩："<<stu.fScore[0]<<",\t"<<stu.fScore[1]<<",\t"<<stu.fScore[2]<<endl;
     return os;
}
istream& operator>> ( istream& is, CStudent& stu )
{
     cout<<"请输入学生信息"<<endl;
     cout<<"姓名：";         is>>stu.strName;
     cout<<"学号：";         is>>stu.strID;
     cout<<"三门成绩：";     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 文件流及其处理

#include <iostream.h>
#include<fstream.h>                  // 文件操作所必需的头文件
int  main()
{
    fstream  file1;                  // 定义一个fstream类的对象用于读
    file1.open("Ex_DataFile.txt", ios::in);
    if (!file1)
    {
        cout<<"Ex_DataFile.txt不能打开！\n";    return;
    }
    fstream  file2;                  // 定义一个fstream类的对象用于写
    file2.open("Ex_DataFileBak.txt", ios::out | ios::trunc);
    if (!file2)
    {
        cout<<"Ex_DataFileBak.txt不能创建！\n"; file1.close();   return;
    }
    char ch;
    while (!file1.eof())
    {
        file1.read(&ch,1);   cout<<ch;     file2.write(&ch,1);
    }
    file2.close();                    // 不要忘记文件使用结束后要及时关闭
    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];                  // 学号
    float fScore;                    // 成绩
};
CStudent::CStudent(char* name, char* id, float score)
{
    strncpy(strName,name,10);      strncpy(strID,id,10);      fScore=score;
}
void CStudent::print()
{
    cout<<endl<<"学生信息如下："<<endl;
    cout<<"姓名："<<strName<<endl;
    cout<<"学号："<<strID<<endl;
    cout<<"成绩："<<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;
}