std::ios_base::pword
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<metanoindex/>
<tbody> </tbody> void*& pword( int index ); |
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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. The text has been machine-translated via Google Translate.
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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.The text has been machine-translated via Google Translate.
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Se a alocação falhar, chama
std::basic_ios<>::setstate(badbit) que pode lançar std::basic_ios::failureOriginal:
If allocation fails, calls
std::basic_ios<>::setstate(badbit) which may throw std::basic_ios::failureThe text has been machine-translated via Google Translate.
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Parâmetros
| index | - | valor do índice do elemento
Original: index value of the element The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Valor de retorno
referência para o elemento
Original:
reference to the element
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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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Exemplo
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';
}
Saída:
cout, narrow-character test
myout, narrow-character test [special handling for mystream]
wcout, wide-character test
mywout, wide-character test [special handling for mystream]
Veja também
redimensiona a armazenagem privada, se necessário e acesso ao elemento long no índice fornecidoOriginal: resizes the private storage if necessary and access to the long element at the given indexThe text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro) | |
[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() The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função public static membro) |