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mbsinit

Defined in header `<wchar.h>`
int mbsinit( const mbstate_t* ps);		(since C95)

If ps is not a null pointer, the mbsinit function determines whether the pointed-to mbstate_t object describes the initial conversion state.

Notes

Although a zero-initialized mbstate_t always represents the initial conversion state, there may be other values of mbstate_t that also represent the initial conversion state.

Parameters

pointer to the mbstate_t object to examine

Return value

0 if ps is not a null pointer and does not represent the initial conversion state, nonzero value otherwise.

Example

#include <locale.h>
#include <string.h>
#include <stdio.h>
#include <wchar.h>
 
int main(void)
{
    // allow mbrlen() to work with UTF-8 multibyte encoding
    setlocale(LC_ALL, "en_US.utf8");
    // UTF-8 narrow multibyte encoding
    const char* str = u8"水"; // or u8"\u6c34" or "\xe6\xb0\xb4"
    static mbstate_t mb; // zero-initialize
    (void)mbrlen(&str[0], 1, &mb);
    if (!mbsinit(&mb)) {
        printf("After processing the first 1 byte of %s,\n"
               "the conversion state is not initial\n\n", str);
    }
 
    (void)mbrlen(&str[1], strlen(str), &mb);
    if (mbsinit(&mb)) {
        printf("After processing the remaining 2 bytes of %s,\n"
               "the conversion state is initial conversion state\n", str);
    }
}

Output:

After processing the first 1 byte of 水,
the conversion state is not initial
 
After processing the remaining 2 bytes of 水,
the conversion state is initial conversion state

References

C17 standard (ISO/IEC 9899:2018):

7.29.6.2.1 The mbsinit function (p: 322)

C11 standard (ISO/IEC 9899:2011):

7.29.6.2.1 The mbsinit function (p: 441-442)

C99 standard (ISO/IEC 9899:1999):

7.24.6.2.1 The mbsinit function (p: 387-388)