MBRTOWC(3)

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 L'\0', it returns the number of bytes that were consumed from s. If the converted wide character is L'\0', 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, excepts 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-L'\0' wide character was recognized. It returns 0, if a L'\0' 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 behaviour of mbrtowc() depends on the LC_CTYPE category of the current locale.

SEE ALSO
mbsrtowcs(3)