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std::ios_base::pword

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< cpp‎ | io‎ | ios base

 
 
De entrada / saída da biblioteca
I / O manipuladores
C estilo de I / O
Buffers
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Buffers
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basic_streambuf
basic_filebuf
basic_stringbuf
strstreambuf(obsoleta)
Streams
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Streams
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Abstrações
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Abstractions
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ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I / O
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File I/O
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basic_ifstream
basic_ofstream
basic_fstream
Cordas I / O
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String I/O
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basic_istringstream
basic_ostringstream
basic_stringstream
Matriz de I / O
Original:
Array I/O
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istrstream(obsoleta)
ostrstream(obsoleta)
strstream(obsoleta)
Tipos
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Types
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streamoff
streamsize
fpos
Interface de categoria de erro
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Error category interface
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iostream_category(C++11)
io_errc(C++11)
 
std::ios_base
Funções de membro
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Member functions
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ios_base::ios_base
ios_base::~ios_base
Formatação
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Formatting
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ios_base::flags
ios_base::setf
ios_base::unsetf
ios_base::precision
ios_base::width
Localidades
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Locales
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ios_base::imbue
ios_base::getloc
Matriz extensível interno
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Internal extensible array
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ios_base::xalloc
ios_base::iword
ios_base::pword
Diversos
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Miscellaneous
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ios_base::register_callback
ios_base::sync_with_stdio
Aulas-Membros
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Member classes
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ios_base::failure
ios_base::Init
Tipos de membro
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Member types
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ios_base::openmode
ios_base::fmtflags
ios_base::iostate
ios_base::seekdir
ios_base::event
ios_base::event_callback
 
void*& pword( int index );
Em primeiro lugar, aloca ou redimensiona a armazenagem privada (matriz dinâmica de void* ou de outra estrutura de dados indexável) o suficiente para fazer index um índice válido, em seguida, devolve uma referência para o elemento void* da armazenagem privada com o índice index.
Original:
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.
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A referência pode ser invalidada por qualquer operação sobre esse objeto ios_base, incluindo outra chamada para pword(), mas os valores armazenados são mantidas, de modo que a leitura de pword(index) com o mesmo índice mais tarde irá produzir o mesmo valor (até a próxima chamada para copyfmt()). O valor pode ser usado para qualquer finalidade. O índice do elemento deve ser obtido por xalloc(), caso contrário, as colisões com outros usuários deste ios_base podem ocorrer. Novos elementos são inicializados para NULL.
Original:
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.
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Se a alocação falhar, chama std::basic_ios<>::setstate(badbit) que pode lançar std::basic_ios::failure
Original:
If allocation fails, calls std::basic_ios<>::setstate(badbit) which may throw std::basic_ios::failure
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Índice

[editar] Parâmetros

index -
valor do índice do elemento
Original:
index value of the element
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[editar] Valor de retorno

referência para o elemento
Original:
reference to the element
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[editar] Exceções

Pode lançar std::ios_base::failure ao definir o badbit.
Original:
May throw std::ios_base::failure when setting the badbit.
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[editar] Exemplo

[edit]

Usa base de classe de armazenamento pword para identificação do tipo de tempo de execução de objetos de fluxo derivados .
Original:
Uses base class pword storage for runtime type identification of derived stream objects.
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#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';
}

Output:

cout, narrow-character test 
myout, narrow-character test [special handling for mystream]
wcout, wide-character test 
mywout, wide-character test [special handling for mystream]

[editar] Veja também

redimensiona a armazenagem privada, se necessário e acesso ao elemento long no índice fornecido
Original:
resizes the private storage if necessary and access to the long element at the given index
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(função pública membro) [edit]
[estática]
retorna um inteiro todo o programa original que é seguro para utilização como índice para pword () e iword ()
Original:
returns a program-wide unique integer that is safe to use as index to pword() and iword()
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(função public static membro) [edit]