标准库头文件 <istream>

 

C++

语言

标准库头文件

自立与有宿主实现

具名要求

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诊断库

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本地化库

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正则表达式库 (C++11)

原子操作库 (C++11)

线程支持库 (C++11)

技术规范

 

标准库头文件

语言支持
<cstddef> <cstdlib> <version> <limits> <climits>	<cfloat> <cstdint> <new> <typeinfo>	<source_location> <exception> <initializer_list>     <compare>	<coroutine> <csignal> <csetjmp> <cstdarg>
概念
<concepts>
诊断
<stdexcept>	<cassert>	<cerrno>	<system_error>
通用工具
<utility> <memory> <memory_resource> <scoped_allocator>	<bitset> <tuple> <optional> <any>	<variant> <type_traits> <ratio> <chrono>	<typeindex> <functional> <stacktrace> <ctime>
字符串
<string> <string_view> <cstring>	<charconv> <format>	<cctype> <cwctype>	<cwchar> <cuchar>
本地化
<locale>	<codecvt>	<clocale>
容器
<span> <array> <vector>	<deque> <forward_list> <list>	<map> <set> <queue>	<unordered_map> <unordered_set> <stack>
迭代器
<iterator>
范围
<ranges>
算法
<algorithm>	<execution>
数值
<complex> <random>	<valarray> <numeric>	<bit> <numbers>	<cfenv> <cmath>
输入/输出
<iosfwd> <ios> <iomanip> <streambuf>	<istream> <ostream> <iostream>	<sstream> <spanstream> <fstream> <syncstream>	<cstdio> <cinttypes> <strstream>
正则表达式
<regex>
文件系统
<filesystem>
线程支持
<thread> <atomic> <mutex>	<shared_mutex> <condition_variable>     <future>	<stop_token> <semaphore>	<latch> <barrier>
C 兼容
<ciso646> <cstdalign>	<cstdbool> <ccomplex>	<ctgmath> <stdatomic.h>

 

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);
  };
}