【C++ Primer】【学习笔记】【第八章】标准IO库之：条件状态

朱雀 2022-08-06 10:21 108阅读 0赞

**一、IO标准库的条件状态**

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      操作 
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      含义 
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      stream::iostate 
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   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:511px"> 条件状态对应的类型名称。</td> 
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      stream::badbit 
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      stream::iostate类型的值，用于指出被破坏的流。 
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      stream::failbit 
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   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:511px"> <span style="font-family:微软雅黑; font-size:14px">stream::iostate类型的值，用于指出失败的IO操作。</span><br style="background-color:inherit"> </td> 
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      stream::eofbit 
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     <span style="font-family:微软雅黑; font-size:14px">stream::iostate类型的值，用于指出流已经到达EOF。</span> 
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      s.eof() 
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      如果设置了流s的 
     <span style="font-family:微软雅黑; font-size:14px">eofbit值，则返回true。</span> 
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      s.fail() 
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     <span style="font-family:微软雅黑; font-size:14px">如果设置了流s的</span> 
     <span style="font-family:微软雅黑; font-size:14px">failbit值，则返回true。</span> 
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      s.bad() 
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     <span style="font-family:微软雅黑; font-size:14px">如果设置了流s的</span> 
     <span style="font-family:微软雅黑; font-size:14px">badbit值，则返回true。</span> 
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      s.good() 
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      如果流s处于有效状态（即： 
     <span style="font-family:微软雅黑; font-size:14px">eofbit、failbit、badbit均未被设置</span>），则返回true。 
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      s.clear() 
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      将流s中的所有状态都重新设置为有效状态。 
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      s.clear(flag) 
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      将 
     <span style="font-family:微软雅黑; font-size:14.399999618530273px">流s中的指定状态都重新设置为有效状态。flag的类型为<span style="font-size:14.399999618530273px">stream::iostate。</span></span> 
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      s.setstate(flag) 
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      给流s添加指定条件。flag的类型是 
     <span style="font-family:微软雅黑; font-size:14.399999618530273px">stream::iostate。</span> 
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      s.rdstate() 
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     <span style="font-family:微软雅黑; font-size:14.399999618530273px">返回流s的当前条件。返回值的类型是</span> 
     <span style="font-family:微软雅黑; font-size:14.399999618530273px">stream::iostate。</span> 
     <br style="background-color:inherit"> 
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**习题8.3&8.4：流读取操作**

#include <iostream>
    #include <stdexcept>
    using namespace std;
    
    istream& read_stream(istream& in)
    {
        int ival;
    
        while (in >> ival, !in.eof())
        {
            if (in.bad())
            {
                throw runtime_error("IO stream corrupted!");
            }
    
            if (in.fail())
            {
                cout << "Read fail, try again." << endl;
                in.clear();
                in.ignore(2, ' ');
                continue;
            }
    
            // ival is ok, process it
            cout << ival << " ";
        }
    
        cout << endl;
        in.clear();
        return in;
    }
    
    int main()
    {
        double dval;
    
        read_stream(cin);
        cout << "read_stream() finish." << endl;
        cin >> dval;
        cout << dval << endl;
    
        return 0;
    }

[chapter8]$ ./a.out
    1 2 3 4 5 aaa bbb ccc 6 7 8 9 0
    1 2 3 4 5 Read fail, try again.
    Read fail, try again.
    Read fail, try again.
    Read fail, try again.
    Read fail, try again.
    Read fail, try again.
    6 7 8 9 0
    read_stream() finish.
    1.02
    1.02