标准库标头 <iosfwd>

此头文件含有输入/输出库的前置声明。

前置声明
在标头 `<string>` 定义
std::char_traits	描述字符类型的性质的类模板 (类模板)
std::char_traits<char>	(类模板特化)
std::char_traits<wchar_t>	(类模板特化)
std::char_traits<char8_t> (C++20)	(类模板特化)
std::char_traits<char16_t> (C++11)	(类模板特化)
std::char_traits<char32_t> (C++11)	(类模板特化)
在标头 `<memory>` 定义
allocator	默认的分配器 (类模板)
在标头 `<ios>` 定义
basic_ios	管理任意流缓冲 (类模板)
fpos	表示流或文件中的绝对位置 (类模板)
在标头 `<streambuf>` 定义
basic_streambuf	抽象原生设备 (类模板)
在标头 `<ostream>` 定义
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)
在标头 `<istream>` 定义
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)
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)
在标头 `<fstream>` 定义
basic_filebuf	抽象原生文件设备 (类模板)
basic_ifstream	实现高层文件流输入操作 (类模板)
basic_ofstream	实现高层文件流输出操作 (类模板)
basic_fstream	实现高层文件流输入/输出操作 (类模板)
在标头 `<sstream>` 定义
basic_stringbuf	实现原生字符串设备 (类模板)
basic_istringstream	实现高层字符串流输入操作 (类模板)
basic_ostringstream	实现高层字符串流输出操作 (类模板)
basic_stringstream	实现高层字符串流输入/输出操作 (类模板)
在标头 `<syncstream>` 定义
basic_syncbuf (C++20)	同步输出设备的包装 (类模板)
basic_osyncstream (C++20)	同步输出流的包装 (类模板)
在标头 `<strstream>` 定义
strstreambuf (C++98 中弃用)	实现原生字符数组设备 (类)
istrstream (C++98 中弃用)	实现字符数组输入操作 (类)
ostrstream (C++98 中弃用)	实现字符数组输出操作 (类)
strstream (C++98 中弃用)	实现字符数组输入/输出操作 (类)
typedef 与特化
std::streampos	std::fpos<std::char_traits<char>::state_type>
std::wstreampos	std::fpos<std::char_traits<wchar_t>::state_type>
std::u8streampos	std::fpos<std::char_traits<char8_t>::state_type>
std::u16streampos	std::fpos<std::char_traits<char16_t>::state_type>
std::u32streampos	std::fpos<std::char_traits<char32_t>::state_type>
另外，对于每个声明于此头文件的类模板 `std::basic_T`，分别声明了 `std::T` 和 `std::wT` 为 `std::basic_T<char>` 和 `std::basic_T<wchar_t>` 的同义词。

概要

namespace std {
  template<class CharT> struct char_traits;
  template<> struct char_traits<char>;
  template<> struct char_traits<char8_t>;
  template<> struct char_traits<char16_t>;
  template<> struct char_traits<char32_t>;
  template<> struct char_traits<wchar_t>;
 
  template<class T> class allocator;
 
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ios;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_streambuf;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_istream;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ostream;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_iostream;
 
  template<class CharT, class Traits = char_traits<CharT>>
           class Allocator = allocator<CharT>>
    class basic_stringbuf;
  template<class CharT, class Traits = char_traits<CharT>>
           class Allocator = allocator<CharT>>
    class basic_istringstream;
  template<class CharT, class Traits = char_traits<CharT>>
           class Allocator = allocator<CharT>>
    class basic_ostringstream;
  template<class CharT, class Traits = char_traits<CharT>>
           class Allocator = allocator<CharT>>
    class basic_stringstream;
 
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_filebuf;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ifstream;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ofstream;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_fstream;
 
  template<class CharT, class Traits = char_traits<CharT>>
           class Allocator = allocator<CharT>>
    class basic_syncbuf;
  template<class CharT, class Traits = char_traits<CharT>>
           class Allocator = allocator<CharT>>
    class basic_osyncstream;
 
  template<class CharT, class Traits = char_traits<CharT>>
    class istreambuf_iterator;
  template<class CharT, class Traits = char_traits<CharT>>
    class ostreambuf_iterator;
 
  using ios  = basic_ios<char>;
  using wios = basic_ios<wchar_t>;
 
  using streambuf = basic_streambuf<char>;
  using istream   = basic_istream<char>;
  using ostream   = basic_ostream<char>;
  using iostream  = basic_iostream<char>;
 
  using stringbuf     = basic_stringbuf<char>;
  using istringstream = basic_istringstream<char>;
  using ostringstream = basic_ostringstream<char>;
  using stringstream  = basic_stringstream<char>;
 
  using filebuf  = basic_filebuf<char>;
  using ifstream = basic_ifstream<char>;
  using ofstream = basic_ofstream<char>;
  using fstream  = basic_fstream<char>;
 
  using syncbuf     = basic_syncbuf<char>;
  using osyncstream = basic_osyncstream<char>;
 
  using wstreambuf = basic_streambuf<wchar_t>;
  using wistream   = basic_istream<wchar_t>;
  using wostream   = basic_ostream<wchar_t>;
  using wiostream  = basic_iostream<wchar_t>;
 
  using wstringbuf     = basic_stringbuf<wchar_t>;
  using wistringstream = basic_istringstream<wchar_t>;
  using wostringstream = basic_ostringstream<wchar_t>;
  using wstringstream  = basic_stringstream<wchar_t>;
 
  using wfilebuf  = basic_filebuf<wchar_t>;
  using wifstream = basic_ifstream<wchar_t>;
  using wofstream = basic_ofstream<wchar_t>;
  using wfstream  = basic_fstream<wchar_t>;
 
  using wsyncbuf     = basic_syncbuf<wchar_t>;
  using wosyncstream = basic_osyncstream<wchar_t>;
 
  template<class State> class fpos;
  using streampos = fpos<char_traits<char>::state_type>;
  using wstreampos = fpos<char_traits<wchar_t>::state_type>;
  using u8streampos = fpos<char_traits<char8_t>::state_type>;
  using u16streampos = fpos<char_traits<char16_t>::state_type>;
  using u32streampos = fpos<char_traits<char32_t>::state_type>;
}
 
// 弃用
namespace std {
  class strstreambuf;
  class istrstream;
  class ostrstream;
  class strstream;
}

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字符串库
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外部库

标准库标头 <iosfwd>

前置声明

typedef 与特化

概要

导航