std::mbrlen - cppreference.com

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Definido no cabeçalho `<cwchar>`

`std::size_t mbrlen( const char* s, std::size_t n, std::mbstate_t* ps);`

Determina o tamanho, em bytes, do restante do caractere multibyte cujo primeiro byte é apontado por s, dado o estado de conversão atual ps.

Original:

Determines the size, in bytes, of the remainder of the multibyte character whose first byte is pointed to by s, given the current conversion state ps.

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Esta função é equivalente à std::mbrtowc(nullptr, s, n, ps?ps:&internal) chamada para internal objeto escondido de std::mbstate_t tipo, exceto que o ps expressão é avaliada apenas uma vez.

Original:

This function is equivalent to the call std::mbrtowc(nullptr, s, n, ps?ps:&internal) for some hidden object internal of type std::mbstate_t, except that the expression ps is evaluated only once.

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Parâmetros

s	-	ponteiro para um elemento de uma cadeia de caracteres multibyte Original: pointer to an element of a multibyte character string The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
n	-	limitar o número de bytes em s que podem ser examinados Original: limit on the number of bytes in s that can be examined The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
ps	-	ponteiro para a variável que contém o estado de conversão Original: pointer to the variable holding the conversion state 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

0 se o n seguinte ou menos bytes completar o caractere nulo.

Original:

0 if the next n or fewer bytes complete the null character.

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O número de bytes (entre 1 e n) que completam um caractere multibyte válido

Original:

The number of bytes (between 1 and n) that complete a valid multibyte character

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(size_t)-1 se ocorre erro de codificação

Original:

(size_t)-1 if encoding error occurs

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(size_t)-2 se os bytes n próximos são parte de um caractere multibyte possivelmente válidos, que ainda está incompleta depois de examinar todos os bytes n

Original:

(size_t)-2 if the next n bytes are part of a possibly valid multibyte character, which is still incomplete after examining all n bytes

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Exemplo

#include <clocale>
#include <string>
#include <iostream>
#include <cwchar>

int main()
{
    // allow mbrlen() to work with UTF-8 multibyte encoding
    std::setlocale(LC_ALL, "en_US.utf8");
    // UTF-8 narrow multibyte encoding
    std::string str = u8"水"; // or u8"\u6c34" or "\xe6\xb0\xb4"
    std::mbstate_t mb = std::mbstate_t();
    int len1 = std::mbrlen(&str[0], 1, &mb);
    if(len1 == -2) {
        std::cout << "The first 1 byte of " << str
                  << " is an incomplete multibyte char (mbrlen returns -2)\n";
    }
    int len2 = std::mbrlen(&str[1], str.size()-1, &mb);
    std::cout << "The remaining " << str.size()-1 << " bytes of " << str
              << " hold " << len2 << " bytes of the multibyte character\n";
    std::cout << "Attempting to call mbrlen() in the middle of " << str
              << " while in initial shift state returns "
              << (int)mbrlen(&str[1], str.size(), &mb) << '\n';

}

Saída:

The first 1 byte of 水 is an incomplete multibyte char (mbrlen returns -2)
The remaining 2 bytes of 水 hold 2 bytes of the multibyte character
Attempting to call mbrlen() in the middle of 水 while in initial shift state returns -1

Veja também


mbrtowc	converte o caractere multibyte ao lado de caráter amplo, determinado estado Original: converts the next multibyte character to wide character, given state The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função) [edit]

mblen	retorna o número de bytes no caractere multibyte seguinte Original: returns the number of bytes in the next multibyte character The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função) [edit]

do_length [virtual]	calcula o comprimento da corda externT que seria consumida por conversão em tampão internt dado Original: calculates the length of the externT string that would be consumed by conversion into given internT buffer The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (virtual protegido of `std::codecvt` função de membro) [edit]

Documentação C para mbrlen