OpenBSD manual page server

Manual Page Search Parameters

MBSTOWCS(3) Library Functions Manual MBSTOWCS(3)

mbstowcsconverts a multibyte character string to a wide-character string

#include <stdlib.h>

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

mbstowcs() converts a null-terminated multibyte character string pointed to by s to the corresponding wide-character string and stores up to n wide characters in the array pointed to by pwcs. Each character will be converted as if mbtowc(3) is continuously called, except the internal state of mbtowc(3) will not be affected.

For state-dependent encoding, mbstowcs() implies the multibyte character string pointed to by s always begin with an initial state.

These are the special cases:

pwcs == NULL
mbstowcs() returns the number of elements to store the whole wide-character string corresponding to the multibyte character string pointed to by s. In this case, n is ignored.
s == NULL
Undefined (may cause the program to crash).

mbstowcs() returns:

0 or positive
The value returned is the number of elements stored in the array pointed to by pwcs, except for a terminating null wide character (if any). If pwcs is not null and the value returned is equal to n, the wide-character string pointed to by pwcs is not null terminated. If pwcs is a null pointer, the value returned is the number of elements to contain the whole string converted, except for a terminating null wide character.
(size_t)-1
The array indirectly pointed to by s contains a byte sequence forming invalid character. In this case, mbstowcs() sets errno to indicate the error.

mbstowcs() may cause an error in the following cases:

[]
s points to the string containing invalid or incomplete multibyte character.

mbtowc(3), setlocale(3)

The mbstowcs() function conforms to ANSI X3.159-1989 (“ANSI C89”). The restrict qualifier is added at ISO/IEC 9899/199 (“ISO C99”).

October 24, 2015 OpenBSD-current