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    std::mbrtowc

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    <metanoindex/>

     
    C++
     
    Stringhe libreria
    Null-stringhe terminate
    Original:
    Null-terminated strings
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    Byte stringhe
    Multibyte stringhe
    Stringhe larghe
    Classi
    Original:
    Classes
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    basic_string
    char_traits
     
    Stringhe multibyte null-terminated
    Wide / multibyte conversioni
    Original:
    Wide/multibyte conversions
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    mbsinit
    Tipi
    Original:
    Types
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    mbstate_t
     
    <tbody> </tbody>
    Elemento definito nell'header <cwchar>
    std::size_t mbrtowc( wchar_t* pwc, const char* s, std::size_t n, std::mbstate_t* ps );
    Converte un carattere multibyte stretto a un carattere ampio.
    Original:
    Converts a narrow multibyte character to a wide character.
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    Se s non è un puntatore nullo, controlla la maggior parte a byte n della stringa di caratteri multibyte, a cominciare con il byte puntato da s per determinare il numero di byte necessari per completare il carattere successivo multibyte (incluse le sequenze di cambio). Se la funzione determina che il carattere multibyte successivo s sia completo e valido, lo converte il carattere corrispondente ampia e lo memorizza in *pwc (se pwc non è nullo).
    Original:
    If s is not a null pointer, inspects at most n bytes of the multibyte character string, beginning with the byte pointed to by s to determine the number of bytes necessary to complete the next multibyte character (including any shift sequences). If the function determines that the next multibyte character in s is complete and valid, converts it to the corresponding wide character and stores it in *pwc (if pwc is not null).
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    Se s è un puntatore nullo, i valori di n e pwc vengono ignorati e chiamata è equivalente a std::mbrtowc(NULL, "", 1, ps).
    Original:
    If s is a null pointer, the values of n and pwc are ignored and call is equivalent to std::mbrtowc(NULL, "", 1, ps).
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    Se il carattere largo prodotto è il carattere nullo, lo stato di conversione memorizzate nel *ps è lo stato iniziale del cambio.
    Original:
    If the wide character produced is the null character, the conversion state stored in *ps is the initial shift state.
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    Parametri

    pwc -
    puntatore nella posizione in cui il personaggio risultante gamma verrà scritto
    Original:
    pointer to the location where the resulting wide character will be written
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    s -
    puntatore alla stringa di caratteri multibyte utilizzati come input
    Original:
    pointer to the multibyte character string used as input
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    n -
    limitare il numero di byte in s che può essere esaminato
    Original:
    limit on the number of bytes in s that can be examined
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    ps -
    puntatore allo stato di conversione quando si interpreta la stringa multibyte
    Original:
    pointer to the conversion state used when interpreting the multibyte string
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    Valore di ritorno

    La prima delle seguenti che vale:
    Original:
    The first of the following that applies:
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    • 0 se il carattere convertito da s (e conservato in pwc se non nullo) è stato il carattere null
      Original:
      0 if the character converted from s (and stored in pwc if non-null) was the null character
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    • il numero di byte [1...n] del carattere multibyte correttamente convertito da s
      Original:
      the number of bytes [1...n] of the multibyte character successfully converted from s
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    • static_cast<std::size_t>(-2) se i byte n prossimi costituiscono un incompleto, ma finora valido, caratteri multibyte. Nulla è scritto *pwc.
      Original:
      static_cast<std::size_t>(-2) if the next n bytes constitute an incomplete, but so far valid, multibyte character. Nothing is written to *pwc.
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    • static_cast<std::size_t>(-1) se si verifica errore di codifica. Nulla viene scritto *pwc, il EILSEQ valore viene memorizzato nella errno e il valore di *ps è lasciato non specificato.
      Original:
      static_cast<std::size_t>(-1) if encoding error occurs. Nothing is written to *pwc, the value EILSEQ is stored in errno and the value of *ps is left unspecified.
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    Esempio

    #include <iostream>
#include <clocale>
#include <cstring>
#include <cwchar>
 
void print_mb(const char* ptr)
{
    std::mbstate_t state = std::mbstate_t(); // initial state
    const char* end = ptr + std::strlen(ptr);
    int len;
    wchar_t wc;
    while((len = std::mbrtowc(&wc, ptr, end-ptr, &state)) > 0) {
        std::wcout << "Next " << len << " bytes are the character " << wc << '\n';
        ptr += len;
    }
}

int main()
{
    std::setlocale(LC_ALL, "en_US.utf8");
    // UTF-8 narrow multibyte encoding
    const char* str = u8"z\u00df\u6c34\U0001d10b"; // or u8"zß水𝄋"
                      // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";
    print_mb(str);
}

    Output: 

    Next 1 bytes are the character z
Next 2 bytes are the character ß
Next 3 bytes are the character 水
Next 4 bytes are the character 𝄋

    Vedi anche
    converte il carattere successivo multibyte a carattere esteso
    Original:
    converts the next multibyte character to wide character
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    (funzione) [modifica]
    converte un carattere esteso alla sua rappresentazione multibyte, determinato stato
    Original:
    converts a wide character to its multibyte representation, given state
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    (funzione) [modifica]
    [virtuale]
    converte una stringa da externT a internt, come ad esempio durante la lettura dal file
    Original:
    converts a string from externT to internT, such as when reading from file
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    (virtuale protetto funzione of std::codecvt membro) [modifica]
    C documentation for mbrtowc