std::ios_base::pword
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| void*& pword( int index ); |
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首先，分配或调整大小的的私人存储（void*的动态数组或其他可转位数据结构）足以使
index一个有效的索引，然后返回一个引用的私有存储与索引void*index元素. 原文：
First, allocates or resizes the private storage (dynamic array of void* or another indexable data structure) sufficiently to make
index a valid index, then returns a reference to the void* element of the private storage with the index index. 参考这
ios_base对象的任何操作无效，包括pword()的另一个调用，但是存储的值将被保留，因此，阅读从pword(index)使用相同的索引后会产生相同的值，直到下一次调用copyfmt()。该值可以用于任何目的。 xalloc()必须通过以下方式获得的元素的索引，否则本ios_base与其他用户的碰撞可能会发生。新的元素被初始化为NULL.原文：
The reference may be invalidated by any operation on this
ios_base object, including another call to pword(), but the stored values are retained, so that reading from pword(index) with the same index later will produce the same value (until the next call to copyfmt()). The value can be used for any purpose. The index of the element must be obtained by xalloc(), otherwise collisions with other users of this ios_base may occur. New elements are initialized to NULL.如果分配失败，调用std::basic_ios<>::setstate(badbit)可能会引发std::basic_ios::failure
原文：
If allocation fails, calls std::basic_ios<>::setstate(badbit) which may throw std::basic_ios::failure
目录 |
[编辑] 参数
| index | - | 的元素的索引值
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[编辑] 返回值
参考的元素
[编辑] 例外
可能会引发std::ios_base::failure时设置的badbit的.
原文：
May throw std::ios_base::failure when setting the badbit.
[编辑] 示例
衍生流对象的运行时类型识别使用基类PWORD的存储空间.
原文：
Uses base class pword storage for runtime type identification of derived stream objects.
#include <iostream> template<class charT, class traits = std::char_traits<charT> > class mystream : public std::basic_ostream<charT, traits> { public: static const int xindex; mystream(std::basic_ostream<charT, traits>& ostr) : std::basic_ostream<charT, traits>(ostr.rdbuf()) { this->pword(xindex) = this; } void myfn() { *this << "[special handling for mystream]"; } }; // each specialization of mystream obtains a unique index from xalloc() template<class charT, class traits> const int mystream<charT, traits>::xindex = std::ios_base::xalloc(); // This I/O manipulator will be able to recognize ostreams that are mystreams // by looking up the pointer stored in pword template<class charT, class traits> std::basic_ostream<charT,traits>& mymanip(std::basic_ostream<charT,traits>& os) { if (os.pword(mystream<charT,traits>::xindex) == &os) static_cast<mystream<charT,traits>&>(os).myfn(); return os; } int main() { std::cout << "cout, narrow-character test " << mymanip << '\n'; mystream<char> myout(std::cout); myout << "myout, narrow-character test " << mymanip << '\n'; std::wcout << "wcout, wide-character test " << mymanip << '\n'; mystream<wchar_t> mywout(std::wcout); mywout << "mywout, wide-character test " << mymanip << '\n'; }
输出：
cout, narrow-character test myout, narrow-character test [special handling for mystream] wcout, wide-character test mywout, wide-character test [special handling for mystream]
[编辑] 另请参阅
| 调整大小的私人存储，如果必要的，访问long元素在给定的索引 原文： resizes the private storage if necessary and access to the long element at the given index （公共成员函数） | |
| [静态的]</div></div>
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返回一个程序范围内唯一的整数，它是安全使用指数PWORD（）和iword（） 原文： returns a program-wide unique integer that is safe to use as index to pword() and iword() （公共静态成员函数） |
