标准库标头 <iosfwd>

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C++
 
标准库头
通用工具
<any> (C++17)
<bitset>
<bit> (C++20)
<charconv> (C++17)
<expected> (C++23)
<format> (C++20)
<functional>
<optional> (C++17)
<stdbit.h> (C++26)
<tuple> (C++11)
<typeindex> (C++11)
<utility>
<variant> (C++17)
容器
<array> (C++11)
<deque>
<flat_map> (C++23)
<flat_set> (C++23)
<forward_list> (C++11)
<hive> (C++26)
<inplace_vector> (C++26)   
<list>
<map>
<mdspan> (C++23)
<queue>
<set>
<span> (C++20)
<stack>
<unordered_map> (C++11)
<unordered_set> (C++11)
<vector>
迭代器
<iterator>
范围
<generator> (C++23)
<ranges> (C++20)
 

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
默认的分配器
(类模板) [编辑]
在标头 <ios> 定义
管理任意流缓冲
(类模板) [编辑]
表示流或文件中的绝对位置
(类模板) [编辑]
在标头 <streambuf> 定义
抽象原生设备
(类模板) [编辑]
在标头 <ostream> 定义
包装给定的抽象设备（std::basic_streambuf）
并提供高层输出接口
(类模板) [编辑]
在标头 <istream> 定义
包装给定的抽象设备（std::basic_streambuf）
并提供高层输入接口
(类模板) [编辑]
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) [编辑]
在标头 <fstream> 定义
实现原生文件设备
(类模板) [编辑]
实现高层文件流输入操作
(类模板) [编辑]
实现高层文件流输出操作
(类模板) [编辑]
实现高层文件流输入/输出操作
(类模板) [编辑]
在标头 <sstream> 定义
实现原生字符串设备
(类模板) [编辑]
实现高层字符串流输入操作
(类模板) [编辑]
实现高层字符串流输出操作
(类模板) [编辑]
实现高层字符串流输入/输出操作
(类模板) [编辑]
在标头 <syncstream> 定义
(C++20)
 同步输出设备的包装器
(类模板) [编辑]
(C++20)
 同步输出流的包装器
(类模板) [编辑]
在标头 <spanstream> 定义
(C++23)
 实现原始固定字符缓冲区设备
(类模板) [编辑]
(C++23)
 实现固定字符缓冲区输入操作
(类模板) [编辑]
(C++23)
 实现固定字符缓冲区输出操作
(类模板) [编辑]
(C++23)
 实现固定字符缓冲区输入/输出操作
(类模板) [编辑]
在标头 <strstream> 定义
(C++98 弃用)(C++26 移除)
 实现原生字符数组设备
(类) [编辑]
(C++98 弃用)(C++26 移除)
 实现字符数组输入操作
(类) [编辑]
(C++98 弃用)(C++26 移除)
 实现字符数组输出操作
(类) [编辑]
(C++98 弃用)(C++26 移除)
 实现字符数组输入/输出操作
(类) [编辑]

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 basic_spanbuf;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ispanstream;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ospanstream;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_spanstream;

  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 spanbuf     = basic_spanbuf<char>;
  using ispanstream = basic_ispanstream<char>;
  using ospanstream = basic_ospanstream<char>;
  using spanstream  = basic_spanstream<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>;

  using wspanbuf     = basic_spanbuf<wchar_t>;
  using wispanstream = basic_ispanstream<wchar_t>;
  using wospanstream = basic_ospanstream<wchar_t>;
  using wspanstream  = basic_spanstream<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;
}