MBRTOWC

Section: Linux Programmer's Manual (3)
Updated: 2001-11-22
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NAME

mbrtowc - convert a multibyte sequence to a wide character

SYNOPSIS

#include <wchar.h>

size_t mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);

DESCRIPTION

The main case for this function is when s is not NULL and pwc is not NULL. In this case, the mbrtowc() function inspects at most n bytes of the multibyte string starting at s, extracts the next complete multibyte character, converts it to a wide character and stores it at *pwc. It updates the shift state *ps. If the converted wide character is not Laq\0aq, it returns the number of bytes that were consumed from s. If the converted wide character is Laq\0aq, it resets the shift state *ps to the initial state and returns 0.

If the n bytes starting at s do not contain a complete multibyte character, mbrtowc() returns (size_t) -2. This can happen even if n >= MB_CUR_MAX, if the multibyte string contains redundant shift sequences.

If the multibyte string starting at s contains an invalid multibyte sequence before the next complete character, mbrtowc() returns (size_t) -1 and sets errno to EILSEQ. In this case, the effects on *ps are undefined.

A different case is when s is not NULL but pwc is NULL. In this case the mbrtowc() function behaves as above, except that it does not store the converted wide character in memory.

A third case is when s is NULL. In this case, pwc and n are ignored. If the conversion state represented by *ps denotes an incomplete multibyte character conversion, the mbrtowc() function returns (size_t) -1, sets errno to EILSEQ, and leaves *ps in an undefined state. Otherwise, the mbrtowc() function puts *ps in the initial state and returns 0.

In all of the above cases, if ps is a NULL pointer, a static anonymous state only known to the mbrtowc function is used instead. Otherwise, *ps must be a valid mbstate_t object. An mbstate_t object a can be initialized to the initial state by zeroing it, for example using

memset(&a, 0, sizeof(a));

RETURN VALUE

The mbrtowc() function returns the number of bytes parsed from the multibyte sequence starting at s, if a non-Laq\0aq wide character was recognized. It returns 0, if a Laq\0aq wide character was recognized. It returns (size_t) -1 and sets errno to EILSEQ, if an invalid multibyte sequence was encountered. It returns (size_t) -2 if it couldn't parse a complete multibyte character, meaning that n should be increased.

CONFORMING TO

C99.

NOTES

The behavior of mbrtowc() depends on the LC_CTYPE category of the current locale.

COLOPHON

This page is part of release 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.