mbrlen_l(3) - Manual pages

NAME

mbrlen, mbrlen_l — get number of bytes in a character (restartable)

SYNOPSIS

#include <wchar.h>

size_t
mbrlen(const char * restrict s, size_t n, mbstate_t * restrict ps);

#include <xlocale.h>

size_t
mbrlen_l(const char * restrict s, size_t n, mbstate_t * restrict ps, locale_t locale);

DESCRIPTION

The mbrlen() and mbrlen_l() functions inspect at most n bytes pointed to by s to determine the number of bytes needed to complete the next multibyte character.

The mbstate_t argument, ps, is used to keep track of the shift state. If it is NULL, mbrlen() and mbrlen_l() use an internal, static mbstate_t object, which is initialized to the initial conversion state at program startup.

It is equivalent to:

mbrtowc(NULL, s, n, ps);

Except that when ps is a NULL pointer, mbrlen() and mbrlen_l() use their own static, internal mbstate_t object to keep track of the shift state.

The mbrlen_l() function takes an explicit locale argument, whereas the mbrlen() function uses the current global or per-thread locale.

RETURN VALUES

The mbrlen() and mbrlen_l() functions return:

0: The next n or fewer bytes represent the null wide character (L'\0').
>0: The next n or fewer bytes represent a valid character, mbrlen() and mbrlen_l() return the number of bytes used to complete the multibyte character.
(size_t)-2: The next n contribute to, but do not complete, a valid multibyte character sequence, and all n bytes have been processed.
(size_t)-1: An encoding error has occurred. The next n or fewer bytes do not contribute to a valid multibyte character.

EXAMPLES

A function that calculates the number of characters in a multibyte character string:

size_t
nchars(const char *s)
{
	size_t charlen, chars;
	mbstate_t mbs;

	chars = 0;
	memset(&mbs, 0, sizeof(mbs));
	while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
	    charlen != (size_t)-1 && charlen != (size_t)-2) {
		s += charlen;
		chars++;
	}

	return (chars);
}

ERRORS

The mbrlen() and mbrlen_l() functions will fail if:

[EILSEQ]: An invalid multibyte sequence was detected.
[EINVAL]: The conversion state is invalid.

STANDARDS

The mbrlen() function conforms to ISO/IEC 9899:1999 (“ISO C99”).

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