wctomb, wctomb_s
From cppreference.com
C
Concurrency support (C11)
Null-terminated multibyte strings
(C95)
(C11)
(C95)
(C95)
(C95)(C11)
(C23)
(C23)
(C11)
(C11)
(C11)
(C11)
wctombwctomb_s
(C11)
(C11)
(C95)
(C95)(C11)
(C95)(C11)
(C95)
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:
-
sszis less than the number of bytes that would be written (unlesssis null) -
sszis greater than RSIZE_MAX (unlesssis null) -
sis a null pointer butsszis not zero
-
- As with all bounds-checked functions,
wctomb_sis 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 including <stdlib.h>.
[edit] 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.
[edit] 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
[edit] 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_MAX[edit] Example
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]
[edit] 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
[edit] See also
C++ documentation for wctomb