mblen(3) Library Functions Manual mblen(3)
NAME
mblen, mbrlen - Determines the length in bytes of a multibyte character
LIBRARY
Standard C Library (libc.so, libc.a)
SYNOPSIS
#include <stdlib.h>
int mblen(
const char *mbs,
size_t n);
#include <wchar.h>
size_t mbrlen(
const char *mbs,
size_t n,
mbstate_t *ps );
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
mblen(): ISO C, XPG4
mbrlen(): ISO C
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Points to a multibyte-character string. Specifies the maximum number of bytes to consider. Points to an mbstate_t structure that contains
the current conversion state of the multibyte-character string.
DESCRIPTION
The mblen() function determines the number of bytes in a multibyte character. The behavior of the mblen() function is affected by the
LC_CTYPE category of the current locale.
In locales with shift-state character encoding, a call to mblen() with a null pointer as the mbs parameter, places the function in the ini-
tial shift state. A call to mblen() with an mbs parameter that is not a null pointer may change the shift state for subsequent calls to
mblen(), depending on the character examined. Changing the LC_CTYPE category of the locale causes the shift state of the function to be
indeterminate. The implementation behaves as though no other function calls the mblen() function.
In the case of nonrestartable functions, such as mblen(), conversion to shift-state encoding must first be enabled by calling the function
with a null pointer parameter and then calling the function again with the wide-character value to be converted. The status of the conver-
sion operation after the call is not available to subsequent calls.
The mbrlen() function is a restartable version of mblen(), which means that, for locales that define state-dependent encoding, the shift
state for the character in mbs is maintained in the mbstate_t structure and is therefore available to subsequent calls by mbrlen() and
other restartable conversion functions.
RESTRICTIONS
The mbrlen() and other restartable versions of conversion routines are functional only when used with locales that support shift-state
encoding. Currently, the Tru64 UNIX product does not provide any locales that use shift-state encoding. Therefore, the mblen() and
mbrlen() functions have the same run-time behavior and always return values for the nonshift-state case.
RETURN VALUES
If the mbs parameter is not a null pointer, the mblen() function returns a value determined as follows: The number of bytes in the charac-
ter, if the number of bytes is n or fewer and if mbs points to a valid multibyte character other than the null character Zero (0), if mbs
points to the null character -1, if mbs does not point to a valid multibyte character or if the length of the character in bytes is more
than the value of the n parameter or the MB_CUR_MAX variable
In this case, mblen() also sets errno to indicate the error.
If mbs is not a null pointer, the mbrlen() function returns the first value that applies in the following list: Zero, if the next n or
fewer bytes constitute a null wide character A positive value indicating the number of bytes in the converted multibyte character, if the
next n or fewer bytes constitute a valid multibyte character (size_t)-2, if the next n bytes contribute to an incomplete (but potentially
valid) multibyte character (size_t)-1, if an encoding error occurs, in which case the next n or fewer bytes do not contribute to a complete
and valid multibyte character
In this case, the mbrlen() function sets errno to indicate the error and the conversion state is undefined.
If the mbs parameter is a null pointer, the mblen() and mbrlen() functions both return one of the following values, depending on whether
the current locale supports shift-state character encoding: A nonzero value, if the character encoding is shift-state dependent Zero (0),
if the character encoding is not shift-state dependent
ERRORS
If the following condition occurs, the mblen() and mbrlen() functions set errno to the corresponding value: The mbs parameter points to an
invalid multibyte character.
RELATED INFORMATION
Functions: btowc(3), mbsinit(3), mbtowc(3), wctomb(3), mbstowcs(3), wcslen(3), wcstombs(3), wctob(3) delim off
mblen(3)