标准库头文件 <ios>

 

C++

编译器支持

独立和宿主

语言

标准库

标准库头文件

命名要求

功能测试宏 (C++20)

语言支持库

概念库 (C++20)

元编程库 (C++11)

诊断库

通用实用程序库

字符串库

容器库

迭代器库

范围库 (C++20)

算法库

数值库

本地化库

输入/输出库

文件系统库 (C++17)

正则表达式库 (C++11)

并发支持库 (C++11)

执行支持库 (C++26)

技术规范

符号索引

外部库

 

标准库头文件

语言支持
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11) <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
概念
<concepts> (C++20)
诊断
<stdexcept> <stacktrace> (C++23)	<cassert>	<cerrno>	<system_error> (C++11)
内存管理
<memory>	<memory_resource> (C++17)	<scoped_allocator> (C++11)
元编程
<type_traits> (C++11)	<ratio> (C++11)
通用实用程序
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <debugging> (C++26) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
字符串
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
容器
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23) <inplace_vector> (C++26)
迭代器
<iterator>
范围
<ranges> (C++20)	<generator> (C++23)
算法
<algorithm>	<numeric>
数值
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath> <linalg> (C++26)	<numbers> (C++20)
时间
<chrono> (C++11)	<ctime>
本地化
<locale>	<clocale>	<codecvt> (C++11/17/26*)	<text_encoding> (C++26)
输入/输出
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98/26*)
正则表达式
<regex> (C++11)
并发支持
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11) <rcu> (C++26)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11) <hazard_pointer> (C++26)
C 兼容性
<cstdbool> (C++11/17/20*)   <ccomplex> (C++11/17/20*)	<ctgmath> (C++11/17/20*)	<cstdalign> (C++11/17/20*)	<ciso646> (直到 C++20)

 

此头文件是 输入/输出 库的一部分。

包含
<iosfwd>	输入/输出库中所有类的转发声明
类
ios_base	管理格式标志和输入/输出异常 (类)
basic_ios	管理任意流缓冲区 (类模板)
std::ios	std::basic_ios<char> (typedef)
std::wios	std::basic_ios<wchar_t> (typedef)
fpos	表示流或文件中的绝对位置 (类模板)
io_errc (C++11)	IO 流错误代码 (枚举)
is_error_code_enum<std::io_errc> (C++11)	扩展类型特质 std::is_error_code_enum 以识别 iostream 错误代码 (类模板特化)
streamoff	表示相对文件/流位置（从 fpos 偏移量），足以表示任何文件大小 (typedef)
streamsize	表示 I/O 操作中传输的字符数或 I/O 缓冲区的大小 (typedef)
函数
iostream_category (C++11)	标识 iostream 错误类别 (函数)
make_error_code(std::io_errc) (C++11)	构造 iostream 错误代码 (函数)
make_error_condition(std::io_errc) (C++11)	构造 iostream 错误条件 (函数)
boolalphanoboolalpha	在布尔值的文本表示和数字表示之间切换 (函数)
showbasenoshowbase	控制是否使用前缀来指示数字基数 (函数)
showpointnoshowpoint	控制浮点表示中是否始终包含小数点 (函数)
showposnoshowpos	控制非负数是否使用 + 符号 (函数)
skipwsnoskipws	控制输入时是否跳过前导空格 (函数)
uppercasenouppercase	控制某些输出格式是否使用大写字符 (函数)
unitbufnounitbuf	控制每次操作后是否刷新输出 (函数)
internalleftright	设置填充字符的位置 (函数)
dechexoct	更改用于整数 I/O 的基数 (函数)
fixedscientifichexfloatdefaultfloat (C++11)(C++11)	更改用于浮点 I/O 的格式 (函数)

概要

#include <iosfwd>
 
namespace std {
  using streamoff  = /* implementation-defined */;
  using streamsize = /* implementation-defined */;
  template<class StateT> class fpos;
 
  class ios_base;
  template<class CharT, class Traits = char_traits<CharT>>
    class basic_ios;
 
  // manipulators
  ios_base& boolalpha  (ios_base& str);
  ios_base& noboolalpha(ios_base& str);
 
  ios_base& showbase   (ios_base& str);
  ios_base& noshowbase (ios_base& str);
 
  ios_base& showpoint  (ios_base& str);
  ios_base& noshowpoint(ios_base& str);
 
  ios_base& showpos    (ios_base& str);
  ios_base& noshowpos  (ios_base& str);
 
  ios_base& skipws     (ios_base& str);
  ios_base& noskipws   (ios_base& str);
 
  ios_base& uppercase  (ios_base& str);
  ios_base& nouppercase(ios_base& str);
 
  ios_base& unitbuf    (ios_base& str);
  ios_base& nounitbuf  (ios_base& str);
 
  // adjustfield
  ios_base& internal   (ios_base& str);
  ios_base& left       (ios_base& str);
  ios_base& right      (ios_base& str);
 
  // basefield
  ios_base& dec        (ios_base& str);
  ios_base& hex        (ios_base& str);
  ios_base& oct        (ios_base& str);
 
  // floatfield
  ios_base& fixed      (ios_base& str);
  ios_base& scientific (ios_base& str);
  ios_base& hexfloat   (ios_base& str);
  ios_base& defaultfloat(ios_base& str);
 
  // error reporting
  enum class io_errc {
    stream = 1
  };
 
  template<> struct is_error_code_enum<io_errc> : public true_type { };
  error_code make_error_code(io_errc e) noexcept;
  error_condition make_error_condition(io_errc e) noexcept;
  const error_category& iostream_category() noexcept;
}

类 std::ios_base

namespace std {
  class ios_base {
  public:
    class failure;              // see description
 
    // fmtflags
    using fmtflags = /*bitmask-type-1*/;
    static constexpr fmtflags boolalpha = /* unspecified */;
    static constexpr fmtflags dec = /* unspecified */;
    static constexpr fmtflags fixed = /* unspecified */;
    static constexpr fmtflags hex = /* unspecified */;
    static constexpr fmtflags internal = /* unspecified */;
    static constexpr fmtflags left = /* unspecified */;
    static constexpr fmtflags oct = /* unspecified */;
    static constexpr fmtflags right = /* unspecified */;
    static constexpr fmtflags scientific = /* unspecified */;
    static constexpr fmtflags showbase = /* unspecified */;
    static constexpr fmtflags showpoint = /* unspecified */;
    static constexpr fmtflags showpos = /* unspecified */;
    static constexpr fmtflags skipws = /* unspecified */;
    static constexpr fmtflags unitbuf = /* unspecified */;
    static constexpr fmtflags uppercase = /* unspecified */;
    static constexpr fmtflags adjustfield = /* see description */;
    static constexpr fmtflags basefield = /* see description */;
    static constexpr fmtflags floatfield = /* see description */;
 
    // iostate
    using iostate = /*bitmask-type-2*/;
    static constexpr iostate badbit = /* unspecified */;
    static constexpr iostate eofbit = /* unspecified */;
    static constexpr iostate failbit = /* unspecified */;
    static constexpr iostate goodbit = /* see description */;
 
    // openmode
    using openmode = /*bitmask-type-3*/;
    static constexpr openmode app = /* unspecified */;
    static constexpr openmode ate = /* unspecified */;
    static constexpr openmode binary = /* unspecified */;
    static constexpr openmode in = /* unspecified */;
    static constexpr openmode out = /* unspecified */;
    static constexpr openmode trunc = /* unspecified */;
    static constexpr openmode noreplace = /* unspecified */
 
    // seekdir
    using seekdir = /*bitmask-type-4*/;
    static constexpr seekdir beg = /* unspecified */;
    static constexpr seekdir cur = /* unspecified */;
    static constexpr seekdir end = /* unspecified */;
 
    class Init;
 
    // fmtflags state
    fmtflags flags() const;
    fmtflags flags(fmtflags fmtfl);
    fmtflags setf(fmtflags fmtfl);
    fmtflags setf(fmtflags fmtfl, fmtflags mask);
    void unsetf(fmtflags mask);
 
    streamsize precision() const;
    streamsize precision(streamsize prec);
    streamsize width() const;
    streamsize width(streamsize wide);
 
    // locales
    locale imbue(const locale& loc);
    locale getloc() const;
 
    // storage
    static int xalloc();
    long&  iword(int idx);
    void*& pword(int idx);
 
    // destructor
    virtual ~ios_base();
 
    // callbacks
    enum event { erase_event, imbue_event, copyfmt_event };
    using event_callback = void (*)(event, ios_base&, int idx);
    void register_callback(event_callback fn, int idx);
 
    ios_base(const ios_base&) = delete;
    ios_base& operator=(const ios_base&) = delete;
 
    static bool sync_with_stdio(bool sync = true);
 
  protected:
    ios_base();
 
  private:
    static int index;           // exposition only
    long*  iarray;              // exposition only
    void** parray;              // exposition only
  };
}

类 std::ios_base::failure

namespace std {
  class ios_base::failure : public system_error {
  public:
    explicit failure(const string& msg, const error_code& ec = io_errc::stream);
    explicit failure(const char* msg, const error_code& ec = io_errc::stream);
  };
}

类 std::ios_base::Init

namespace std {
  class ios_base::Init {
  public:
    Init();
    Init(const Init&) = default;
    ~Init();
    Init& operator=(const Init&) = default;
  private:
    static int init_cnt;        // exposition only
  };
}

类模板 std::fpos

namespace std {
  template<class StateT> class fpos {
  public:
    // members
    StateT state() const;
    void state(stateT);
  private;
    StateT st;                  // exposition only
  };
}

类模板 std::basic_ios

namespace std {
  template<class CharT, class Traits = char_traits<CharT>>
  class basic_ios : public ios_base {
  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;
 
    // flags functions
    explicit operator bool() const;
    bool operator!() const;
    iostate rdstate() const;
    void clear(iostate state = goodbit);
    void setstate(iostate state);
    bool good() const;
    bool eof()  const;
    bool fail() const;
    bool bad()  const;
 
    iostate exceptions() const;
    void exceptions(iostate except);
 
    // constructor/destructor
    explicit basic_ios(basic_streambuf<CharT, Traits>* sb);
    virtual ~basic_ios();
 
    // members
    basic_ostream<CharT, Traits>* tie() const;
    basic_ostream<CharT, Traits>* tie(basic_ostream<CharT, Traits>* tiestr);
 
    basic_streambuf<CharT, Traits>* rdbuf() const;
    basic_streambuf<CharT, Traits>* rdbuf(basic_streambuf<CharT, Traits>* sb);
 
    basic_ios& copyfmt(const basic_ios& rhs);
 
    char_type fill() const;
    char_type fill(char_type ch);
 
    locale imbue(const locale& loc);
 
    char      narrow(char_type c, char dfault) const;
    char_type widen(char c) const;
 
    basic_ios(const basic_ios&) = delete;
    basic_ios& operator=(const basic_ios&) = delete;
 
  protected:
    basic_ios();
    void init(basic_streambuf<CharT, Traits>* sb);
    void move(basic_ios& rhs);
    void move(basic_ios&& rhs);
    void swap(basic_ios& rhs) noexcept;
    void set_rdbuf(basic_streambuf<CharT, Traits>* sb);
  };
}

缺陷报告

以下行为变更缺陷报告已追溯应用于先前发布的 C++ 标准。

DR	应用于	已发布的行为	正确行为
LWG 35	C++98	在概要中缺少 unitbuf 和 nounitbuf 的原型	已添加
LWG 78	C++98	ios_base::register_callback 的参数 fn 的类型 在概要中错误指定为 event_call_back	已更正为 event_callback