# 标准库头文件 <istream>

< cpp‎ | header

此头文件是输入/输出库的一部分。

basic_istream | 包装给定的抽象设备（std::basic_streambuf） 并提供高层输入接口 (类模板)
std::istream | std::basic_istream<char> (typedef)
std::wistream | std::basic_istream<wchar_t> (typedef)
basic_iostream | 包装给定的抽象设备（std::basic_streambuf） 并提供高层输入/输出接口 (类模板)
std::iostream | std::basic_iostream<char> (typedef)
std::wiostream | std::basic_iostream<wchar_t> (typedef)
### 函数
operator>>(std::basic_istream) | 提取字符和字符数组 (函数模板)
##### 操纵符
ws | 消耗空白符 (函数模板)

### 概要

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
        class basic_istream;

      using istream  = basic_istream<char>;
      using wistream = basic_istream<wchar_t>;

      template<class CharT, class Traits = char_traits<CharT>>
        class basic_iostream;

      using iostream  = basic_iostream<char>;
      using wiostream = basic_iostream<wchar_t>;

      template<class CharT, class Traits>
        basic_istream<CharT, Traits>& ws(basic_istream<CharT, Traits>& is);

      template<class Istream, class T>
        Istream&& operator>>(Istream&& is, T&& x);
    }

#### 类模板 std::basic_istream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_istream : virtual public basic_ios<CharT, Traits> {
      public:
        // 类型（继承自 basic_ios ）
        using char_type   = CharT;
        using int_type    = typename Traits::int_type;
        using pos_type    = typename Traits::pos_type;
        using off_type    = typename Traits::off_type;
        using traits_type = Traits;

        // 构造函数/析构函数
        explicit basic_istream(basic_streambuf<CharT, Traits>* sb);
        virtual ~basic_istream();

        // 前置工序/后置工序
        class sentry;

        // 有格式输出
        basic_istream<CharT, Traits>&
          operator>>(basic_istream<CharT, Traits>& (*pf)(basic_istream<CharT, Traits>&));
        basic_istream<CharT, Traits>&
          operator>>(basic_ios<CharT, Traits>& (*pf)(basic_ios<CharT, Traits>&));
        basic_istream<CharT, Traits>&
          operator>>(ios_base& (*pf)(ios_base&));

        basic_istream<CharT, Traits>& operator>>(bool& n);
        basic_istream<CharT, Traits>& operator>>(short& n);
        basic_istream<CharT, Traits>& operator>>(unsigned short& n);
        basic_istream<CharT, Traits>& operator>>(int& n);
        basic_istream<CharT, Traits>& operator>>(unsigned int& n);
        basic_istream<CharT, Traits>& operator>>(long& n);
        basic_istream<CharT, Traits>& operator>>(unsigned long& n);
        basic_istream<CharT, Traits>& operator>>(long long& n);
        basic_istream<CharT, Traits>& operator>>(unsigned long long& n);
        basic_istream<CharT, Traits>& operator>>(float& f);
        basic_istream<CharT, Traits>& operator>>(double& f);
        basic_istream<CharT, Traits>& operator>>(long double& f);

        basic_istream<CharT, Traits>& operator>>(void*& p);
        basic_istream<CharT, Traits>& operator>>(basic_streambuf<char_type, Traits>* sb);

        // 无格式输出
        streamsize gcount() const;
        int_type get();
        basic_istream<CharT, Traits>& get(char_type& c);
        basic_istream<CharT, Traits>& get(char_type* s, streamsize n);
        basic_istream<CharT, Traits>& get(char_type* s, streamsize n, char_type delim);
        basic_istream<CharT, Traits>& get(basic_streambuf<char_type, Traits>& sb);
        basic_istream<CharT, Traits>&
          get(basic_streambuf<char_type, Traits>& sb, char_type delim);

        basic_istream<CharT, Traits>& getline(char_type* s, streamsize n);
        basic_istream<CharT, Traits>& getline(char_type* s, streamsize n, char_type delim);

        basic_istream<CharT, Traits>& ignore(streamsize n = 1, int_type delim = Traits::eof());
        int_type                      peek();
        basic_istream<CharT, Traits>& read    (char_type* s, streamsize n);
        streamsize                    readsome(char_type* s, streamsize n);

        basic_istream<CharT, Traits>& putback(char_type c);
        basic_istream<CharT, Traits>& unget();
        int sync();

        pos_type tellg();
        basic_istream<CharT, Traits>& seekg(pos_type);
        basic_istream<CharT, Traits>& seekg(off_type, ios_base::seekdir);

      protected:
        // 复制/移动构造函数
        basic_istream(const basic_istream&) = delete;
        basic_istream(basic_istream&& rhs);

        // 赋值与交换
        basic_istream& operator=(const basic_istream&) = delete;
        basic_istream& operator=(basic_istream&& rhs);
        void swap(basic_istream& rhs);
      };

      // 字符提取模板
      template<class CharT, class Traits>
        basic_istream<CharT, Traits>& operator>>(basic_istream<CharT, Traits>&, CharT&);
      template<class Traits>
        basic_istream<char, Traits>& operator>>(basic_istream<char, Traits>&, unsigned char&);
      template<class Traits>
        basic_istream<char, Traits>& operator>>(basic_istream<char, Traits>&, signed char&);

      template<class CharT, class Traits, size_t N>
        basic_istream<CharT, Traits>&
          operator>>(basic_istream<CharT, Traits>&, CharT(&)[N]);
      template<class Traits, size_t N>
        basic_istream<char, Traits>&
          operator>>(basic_istream<char, Traits>&, unsigned char(&)[N]);
      template<class Traits, size_t N>
        basic_istream<char, Traits>&
          operator>>(basic_istream<char, Traits>&, signed char(&)[N]);
    }

#### 类 std::basic_istream::sentry

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_istream<CharT, Traits>::sentry {
        bool ok_;                   // 仅用于阐释
      public:
        explicit sentry(basic_istream<CharT, Traits>& is, bool noskipws = false);
        ~sentry();
        explicit operator bool() const { return ok_; }
        sentry(const sentry&) = delete;
        sentry& operator=(const sentry&) = delete;
      };
    }

#### 类模板 std::basic_iostream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_iostream
        : public basic_istream<CharT, Traits>,
          public basic_ostream<CharT, Traits> {
      public:
        using char_type   = CharT;
        using int_type    = typename Traits::int_type;
        using pos_type    = typename Traits::pos_type;
        using off_type    = typename Traits::off_type;
        using traits_type = Traits;

        // 构造函数
        explicit basic_iostream(basic_streambuf<CharT, Traits>* sb);

        // 析构函数
        virtual ~basic_iostream();

      protected:
        // 构造函数
        basic_iostream(const basic_iostream&) = delete;
        basic_iostream(basic_iostream&& rhs);

        // 赋值与交换
        basic_iostream& operator=(const basic_iostream&) = delete;
        basic_iostream& operator=(basic_iostream&& rhs);
        void swap(basic_iostream& rhs);
      };
    }