Name
mbrtowc - convert a multibyte sequence to a wide characterLibrary
Standard C library ( libc ", " -lc )Synopsis
#include <wchar.h> size_t mbrtowc(wchar_t *restrict " pwc ", const char " s "[restrict . n ],
size_t " n ", mbstate_t *restrict 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 ats
, 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'\e0' (the null wide character), it returns the number of bytes that were consumed from s
. If the converted wide character is L'\e0', 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 NULL, a static anonymous state known only 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 ats
, if a non-L'\e0' wide character was recognized. It returns 0, if a L'\e0' 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. Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Unsafe race:mbrtowc/!ps |