wctomb, wctomb_s
From cppreference.com
Defined in header <stdlib.h>
|
||
int wctomb( char *s, wchar_t wc ); |
(1) | |
errno_t wctomb_s( int *restrict status, char *restrict s, rsize_t ssz, wchar_t wc ); |
(2) | (since C11) |
1) Converts a wide character
wc
to multibyte encoding and stores it (including any shift sequences) in the char array whose first element is pointed to by s
. No more than MB_CUR_MAX characters are stored. The conversion is affected by the current locale's LC_CTYPE category. If
wc
is the null character, the null byte is written to s
, preceded by any shift sequences necessary to restore the initial shift state. If
s
is a null pointer, this function resets the global conversion state and determines whether shift sequences are used.2) Same as (1), except that the result is returned in the out-parameter
status
and the following errors are detected at runtime and call the currently installed constraint handler function:
-
ssz
is less than the number of bytes that would be written (unlesss
is null) -
ssz
is greater than RSIZE_MAX (unlesss
is null) -
s
is a null pointer butssz
is not zero
-
- As with all bounds-checked functions,
wctomb_s
is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before includingstdlib.h
.
Notes
Each call to wctomb
updates the internal global conversion state (a static object of type mbstate_t, known only to this function). If the multibyte encoding uses shift states, this function is not reentrant. In any case, multiple threads should not call wctomb
without synchronization: wcrtomb or wctomb_s
may be used instead.
Unlike most bounds-checked functions, wctomb_s
does not null-terminate its output, because it is designed to be used in loops that process strings character-by-character.
Parameters
s | - | pointer to the character array for output |
wc | - | wide character to convert |
ssz | - | maximum number of bytes to write to s (size of the array s )
|
status | - | pointer to an out-parameter where the result (length of the multibyte sequence or the shift sequence status) will be stored |
Return value
1) If
s
is not a null pointer, returns the number of bytes that are contained in the multibyte representation of wc
or -1 if wc
is not a valid character. If
s
is a null pointer, resets its internal conversion state to represent the initial shift state and returns 0 if the current multibyte encoding is not state-dependent (does not use shift sequences) or a non-zero value if the current multibyte encoding is state-dependent (uses shift sequences).2) zero on success, in which case the multibyte representation of
wc
is stored in s
and its length is stored in *status, or, if s
is null, the shift sequence status is stored in status
). Non-zero on encoding error or runtime constraint violation, in which case (size_t)-1 is stored in *status. The value stored in *status never exceeds MB_CUR_MAXExample
Run this code
#include <stdio.h> #include <stdlib.h> #include <locale.h> void demo(wchar_t wc) { const char* dep = wctomb(NULL, wc) ? "Yes" : "No"; printf("State-dependent encoding? %s.\n", dep); char mb[MB_CUR_MAX]; int len = wctomb(mb, wc); printf("wide char '%lc' -> multibyte char [", wc); for (int idx = 0; idx < len; ++idx) printf("%s%#2x", idx ? " " : "", (unsigned char)mb[idx]); printf("]\n"); } int main(void) { setlocale(LC_ALL, "en_US.utf8"); printf("MB_CUR_MAX = %zu\n", MB_CUR_MAX); demo(L'A'); demo(L'\u00df'); demo(L'\U0001d10b'); }
Possible output:
MB_CUR_MAX = 6 State-dependent encoding? No. wide char 'A' -> multibyte char [0x41] State-dependent encoding? No. wide char 'ß' -> multibyte char [0xc3 0x9f] State-dependent encoding? No. wide char '𝄋' -> multibyte char [0xf0 0x9d 0x84 0x8b]
References
- C17 standard (ISO/IEC 9899:2018):
- 7.22.7.3 The wctomb function (p: 261)
- K.3.6.4.1 The wctomb_s function (p: 443)
- C11 standard (ISO/IEC 9899:2011):
- 7.22.7.3 The wctomb function (p: 358-359)
- K.3.6.4.1 The wctomb_s function (p: 610-611)
- C99 standard (ISO/IEC 9899:1999):
- 7.20.7.3 The wctomb function (p: 322-323)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.10.7.3 The wctomb function
See also
converts the next multibyte character to wide character (function) | |
(C95)(C11) |
converts a wide character to its multibyte representation, given state (function) |