# 标准库头文件 <ostream>

< cpp‎ | header

此头文件是输入/输出库的一部分。

### 类
basic_ostream | 包装给定的抽象设备（std::basic_streambuf） 并提供高层输出接口 (类模板)
std::ostream | std::basic_ostream<char> (typedef)
std::wostream | std::basic_ostream<wchar_t> (typedef)
### 函数
operator<<(std::basic_ostream) | 插入字符数据 (函数)
##### 操纵符
endl | 输出 '\n' 并冲洗输出流 (函数模板)
ends | 输出 '\0' (函数模板)
flush | 冲洗输出流 (函数模板)
emit_on_flush noemit_on_flush (C++20) | 控制流的 `basic_syncbuf` 是否在冲入时发射 (函数模板)
flush_emit (C++20) | 冲入流，而若它使用 `basic_syncbuf` 则发射其内容 (函数模板)

### 概要

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

      using ostream  = basic_ostream<char>;
      using wostream = basic_ostream<wchar_t>;

      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& endl(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& ends(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& flush(basic_ostream<CharT, Traits>& os);

      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& emit_on_flush(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& noemit_on_flush(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& flush_emit(basic_ostream<CharT, Traits>& os);

      template<class Ostream, class T>
        Ostream&& operator<<(Ostream&& os, const T& x);
    }

#### 类模板 std::basic_ostream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_ostream : 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_ostream(basic_streambuf<char_type, Traits>* sb);
        virtual ~basic_ostream();

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

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

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

        basic_ostream<CharT, Traits>& operator<<(const void* p);
        basic_ostream<CharT, Traits>& operator<<(const volatile void* val);
        basic_ostream<CharT, Traits>& operator<<(nullptr_t);
        basic_ostream<CharT, Traits>& operator<<(basic_streambuf<char_type, Traits>* sb);

        // 无格式输出
        basic_ostream<CharT, Traits>& put(char_type c);
        basic_ostream<CharT, Traits>& write(const char_type* s, streamsize n);

        basic_ostream<CharT, Traits>& flush();

        // 巡位
        pos_type tellp();
        basic_ostream<CharT, Traits>& seekp(pos_type);
        basic_ostream<CharT, Traits>& seekp(off_type, ios_base::seekdir);

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

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

      // 字符插入器
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>&, CharT);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>&, char);
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, char);

      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, signed char);
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, unsigned char);

      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, wchar_t) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, char8_t) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, char16_t) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, char32_t) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, char8_t) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, char16_t) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, char32_t) = delete;

      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>&
          operator<<(basic_ostream<CharT, Traits>&, const CharT*);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>&
          operator<<(basic_ostream<CharT, Traits>&, const char*);
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char*);

      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const signed char*);
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const unsigned char*);

      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const wchar_t*) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char8_t*) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char16_t*) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char32_t*) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, const char8_t*) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, const char16_t*) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, const char32_t*) = delete;
    }

#### 类 std::basic_ostream::sentry

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

        sentry(const sentry&) = delete;
        sentry& operator=(const sentry&) = delete;
      };
    }