multibyte(3C)

NAME

mblen(), mbtowc(), mbstowcs(), wctomb(), wcstombs() — multibyte characters and strings conversions

SYNOPSIS

#include <stdlib.h>

int mblen(const char *s, size_t n);

int mbtowc(wchar_t *__restrict pwc, const char *__restrict s, size_t n);

int wctomb(char *s, wchar_t wchar);

size_t mbstowcs(wchar_t *__restrict pwcs, const char *__restrict s, size_t n);

size_t wcstombs(char *__restrict s, const wchar_t *__restrict pwcs, size_t n);

DESCRIPTION

A multibyte character is composed of one or more bytes that represent a "whole" character in a character encoding. A wide character (type of wchar_t) is composed of a fixed number of bytes whose code value can represent any character in a character encoding.

mblen()

Determine the number of bytes in the multibyte character pointed to by s. Equivalent to:

mbtowc((wchar_t *)0, s, n);

If s is a null pointer, mblen returns a nonzero or zero value, depending on whether the multibyte character encodings do or do not have state-dependent encodings, respectively. Since no character encodings currently supported by HP-UX are state-dependent, zero is always returned in this case. However, for maximum portability to other systems, application programs should not depend on this.

If s is not a null pointer, mblen returns the number of bytes in the multibyte character if the next n or fewer bytes form a valid multibyte character, or return -1 if they do not form a valid multibyte character. If s points to the null character, mblen returns 0.

mbtowc()

Determine the number of bytes in the multibyte character pointed to by s, determine the code for the value of type wchar_t corresponding to that multibyte character, then store the code in the object pointed to by pwc. The value of the code corresponding to the null character is zero. At most n characters are examined, starting at the character pointed to by s.

If s is a null pointer, mbtowc() returns a non-zero or zero value, depending on whether the multibyte character encodings do or do not have state-dependent encodings, respectively. Since no character encodings currently supported by HP-UX are state-dependent, zero is always returned in this case. However, for maximum portability to other systems, application programs should not depend on this.

If s is not a null pointer, mbtowc() returns the number of bytes in the converted multibyte character if the next n or fewer bytes form a valid multibyte character, or -1 if they do not form a valid multibyte character. If s points to the null character, mbtowc() returns 0. The value returned is never greater than n or the value of the MB_CUR_MAX macro.

wctomb()

Determine the number of bytes needed to represent the multibyte character corresponding to the code whose value is wchar and store the multibyte character representation in the array object pointed to by s. At most MB_CUR_MAX characters are stored.

If s is a null pointer, wctomb() returns a nonzero or zero value, depending on whether the multibyte character encodings do or do not have state-dependent encodings, respectively. Since no character encodings currently supported by HP-UX are state-dependent, zero is always returned in this case. However, for maximum portability to other systems, application programs should not depend on this.

If s is not a null pointer, wctomb() returns the number of bytes in the multibyte character corresponding to the value of wchar, or -1 if the value of wchar does not correspond to a valid multibyte character. The value returned is never greater than the value of the MB_CUR_MAX macro.

mbstowcs()

Convert a sequence of multibyte characters from the array pointed to by s into a sequence of corresponding codes and store these codes into the array pointed to by pwcs, stopping after either n codes or a code with value zero (a converted null character) is stored. Each multibyte character is converted as if by a call to mbtowc(). No more than n elements are modified in the array pointed to by pwcs.

If an invalid multibyte character is encountered, mbstowcs() returns (size_t)-1. Otherwise, mbstowcs() returns the number of array elements modified, not including a terminating zero code, if any. The array is not null- or zero-terminated if the value returned is n. If pwcs is a null pointer, mbstowcs() returns the number of elements required for the wide-character-code array.

wcstombs()

Convert a sequence of codes corresponding to multibyte characters from the array pointed to by pwcs into a sequence of multibyte characters and store them into the array pointed to by s, stopping if a multibyte character exceeds the limit of n total bytes or if a null character is stored. Each code is converted as if by a call to wctomb(). No more than n bytes are modified in the array pointed to by s.

If a code is encountered that does not correspond to a valid multibyte character, wcstombs() returns (size_t)-1. Otherwise, wcstombs() returns the number of bytes modified, not including a terminating null character, if any. The array is not null- or zero-terminated if the value returned is n. If s is a null pointer, wcstombs() returns the number of bytes required for the character array.

EXTERNAL INFLUENCES

Locale

The LC_CTYPE category determines the behavior of the multibyte character and string functions.

ERRORS

mblen(), mbstowcs(), mbtowc(), wcstombs() and wctomb() may fail and errno is set if the following condition is encountered:

[EILSEQ]: An invalid multibyte sequence or wide character code was found.

WARNINGS

With the exception of ASCII characters, the code values of wide characters (type of wchar_t) are specific to the effective locale specified by the LC_CTYPE environment variable. These values may not be compatible with values obtained by specifying other locales that are supported now, or which may be supported in the future. It is recommended that wide character constants and wide string literals (see the C Reference Manual) not be used, and that wide character code values not be stored in files or devices because future standards may dictate changes in the code value assignments of the wide characters. However, wide character constants and wide string literals corresponding to the characters of the ASCII code set can be safely used since their values are guaranteed to be the same as their ASCII code set values.

AUTHOR

The multibyte functions in this entry were developed by OSF and HP.

STANDARDS CONFORMANCE

mblen(): AES, SVID3, XPG4, ANSI C

mbstowcs(): AES, SVID3, XPG4, ANSI C

mbtowc(): AES, SVID3, XPG4, ANSI C

wcstombs(): AES, SVID3, XPG4, ANSI C

wctomb(): AES, SVID3, XPG4, ANSI C