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$FreeBSD: head/lib/libc/locale/mbrlen.3 131360 2004-06-30 19:32:41Z ru $
.Dd April 7, 2004 .Dt MBRLEN 3 .Os .Sh NAME .Nm mbrlen .Nd "get number of bytes in a character (restartable)" .Sh LIBRARY .Lb libc .Sh SYNOPSIS n wchar.h .Ft size_t .Fn mbrlen "const char * restrict s" "size_t n" "mbstate_t * restrict ps" .Sh DESCRIPTION The .Fn mbrlen function inspects at most .Fa n bytes pointed to by .Fa s to determine the number of bytes needed to complete the next multibyte character.
p The .Vt mbstate_t argument, .Fa ps , is used to keep track of the shift state. If it is .Dv NULL , .Fn mbrlen uses an internal, static .Vt mbstate_t object, which is initialized to the initial conversion state at program startup.
p It is equivalent to:
p .Dl "mbrtowc(NULL, s, n, ps);"
p Except that when .Fa ps is a .Dv NULL pointer, .Fn mbrlen uses its own static, internal .Vt mbstate_t object to keep track of the shift state. .Sh RETURN VALUES The .Fn mbrlen functions returns: l -tag -width indent t 0 The next .Fa n or fewer bytes represent the null wide character
q Li "L'\e0'" . t >0 The next .Fa n or fewer bytes represent a valid character, .Fn mbrlen returns the number of bytes used to complete the multibyte character. t Po Vt size_t Pc Ns -2 The next .Fa n contribute to, but do not complete, a valid multibyte character sequence, and all .Fa n bytes have been processed. t Po Vt size_t Pc Ns -1 An encoding error has occurred. The next .Fa n or fewer bytes do not contribute to a valid multibyte character. .El .Sh EXAMPLES A function that calculates the number of characters in a multibyte character string: d -literal -offset indent 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); } .Ed .Sh ERRORS The .Fn mbrlen function will fail if: l -tag -width Er t Bq Er EILSEQ An invalid multibyte sequence was detected. t Bq Er EINVAL The conversion state is invalid. .El .Sh SEE ALSO .Xr mblen 3 , .Xr mbrtowc 3 , .Xr multibyte 3 .Sh STANDARDS The .Fn mbrlen function conforms to .St -isoC-99 .