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std::ios_base::xalloc

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< cpp‎ | io‎ | ios base

 
 
De entrada / saída da biblioteca
I / O manipuladores
C estilo de I / O
Buffers
Original:
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
 
static int xalloc();
Retorna um valor (programa de largura) índice exclusivo que pode ser usado para acessar um long e um void* elementos da armazenagem privada, chamando iword() e pword(). A chamada para xalloc não aloca memória.
Original:
Returns an unique (program-wide) index value that can be used to access one long and one void* elements in the private storage by calling iword() and pword(). The call to xalloc does not allocate memory.
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Índice

[editar] Parâmetros

(Nenhum)
Original:
(none)
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[editar] Valor de retorno

inteiro exclusivo para uso como pword / iword índice
Original:
unique integer for use as pword/iword index
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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 void* no índice fornecido
Original:
resizes the private storage if necessary and access to the void* element at the given index
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(função pública membro) [edit]
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]