标准库头文件 <iosfwd>

 

C++

语言

标准库头文件

自立与有宿主实现

具名要求

语言支持库

概念库 (C++20)

诊断库

工具库

字符串库

容器库

迭代器库

范围库 (C++20)

算法库

数值库

输入/输出库

本地化库

正则表达式库 (C++11)

原子操作库 (C++11)

线程支持库 (C++11)

文件系统库 (C++17)

技术规范

 

标准库头文件

语言支持
<cstddef> <limits> <climits> <coroutine>	<cfloat> <cstdint> <new> <source_location>	<typeinfo> <exception> <initializer_list> <version>	<csignal> <csetjmp> <cstdarg>
概念
<concepts>
诊断
<stdexcept>	<cassert>	<cerrno>	<system_error>
通用工具
<utility> <memory> <memory_resource> <scoped_allocator>     <compare>	<bitset> <tuple> <optional> <any> <variant>	<type_traits> <ratio> <chrono> <typeindex> <functional>	<ctime> <cstdlib>
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> <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>

 

此头文件含有输入/输出库的前置声明。

前置声明
定义于头文件 <string>
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)
定义于头文件 <memory>
allocator	默认的分配器 (类模板)
定义于头文件 <ios>
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)
定义于头文件 <streambuf>
basic_streambuf	抽象原生设备 (类模板)
定义于头文件 <ostream>
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)
定义于头文件 <istream>
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)
定义于头文件 <fstream>
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)
定义于头文件 <sstream>
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)
定义于头文件 <syncstream>
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)
定义于头文件 <strstream>
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	fpos<char_traits<char>::state_type>
std::wstreampos	fpos<char_traits<wchar_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> class char_traits;
    template<> class char_traits<char>;
    template<> class char_traits<char8_t>;
    template<> class char_traits<char16_t>;
    template<> class char_traits<char32_t>;
    template<> class 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;
 
 
    typedef basic_ios<char>     ios;    
    typedef basic_ios<wchar_t>  wios;   
 
    typedef basic_streambuf<char>     streambuf;
    typedef basic_istream<char>       istream;
    typedef basic_ostream<char>       ostream;
    typedef basic_iostream<char>      iostream;
 
    typedef basic_stringbuf<char>     stringbuf;
    typedef basic_istringstream<char> istringstream;
    typedef basic_ostringstream<char> ostringstream;
    typedef basic_stringstream<char>  stringstream;
 
    typedef basic_filebuf<char>       filebuf;
    typedef basic_ifstream<char>      ifstream;
    typedef basic_ofstream<char>      ofstream;
    typedef basic_fstream<char>       fstream;
 
    typedef basic_syncbuf<char>       syncbuf;
    typedef basic_osyncstream<char>   osyncstream;
 
    typedef basic_streambuf<wchar_t>     wstreambuf;
    typedef basic_istream<wchar_t>       wistream;
    typedef basic_ostream<wchar_t>       wostream;
    typedef basic_iostream<wchar_t>      wiostream;
 
    typedef basic_stringbuf<wchar_t>     wstringbuf;
    typedef basic_istringstream<wchar_t> wistringstream;
    typedef basic_ostringstream<wchar_t> wostringstream;
    typedef basic_stringstream<wchar_t>  wstringstream;
 
    typedef basic_filebuf<wchar_t>       wfilebuf;        
    typedef basic_ifstream<wchar_t>      wifstream;      
    typedef basic_ofstream<wchar_t>      wofstream;      
    typedef basic_fstream<wchar_t>       wfstream;
 
    typedef basic_syncbuf<wchar_t>       wsyncbuf;
    typedef basic_osyncstream<wchar_t>   wosyncstream;
 
    template <class state> class fpos;      
    typedef fpos<char_traits<char>::state_type> streampos;  
    typedef fpos<char_traits<wchar_t>::state_type> wstreampos;  
 
}