mbstowcs, mbstowcs_s
From cppreference.com
Defined in header <stdlib.h>
|
||
(1) | ||
(until C99) | ||
(since C99) | ||
errno_t mbstowcs_s(size_t *restrict retval, wchar_t *restrict dst, rsize_t dstsz, const char *restrict src, rsize_t len); |
(2) | (since C11) |
1) Converts a multibyte character string from the array whose first element is pointed to by
src
to its wide character representation. Converted characters are stored in the successive elements of the array pointed to by dst
. No more than len
wide characters are written to the destination array. Each character is converted as if by a call to mbtowc, except that the mbtowc conversion state is unaffected. The conversion stops if:
* The multibyte null character was converted and stored.
* An invalid (in the current C locale) multibyte character was encountered.
* The next wide character to be stored would exceed
len
. If
src
and dst
overlap, the behavior is undefined2) Same as (1), except that
* the function returns its result as an out-parameter
retval
* if no null character was written to
dst
after len
wide characters were written, then L'\0' is stored in dst[len]
, which means len+1 total wide characters are written * if
dst
is a null pointer, the number of wide characters that would be produced is stored in *retval * the function clobbers the destination array from the terminating null and until
dstsz
* If
src
and dst
overlap, the behavior is unspecified. * the following errors are detected at runtime and call the currently installed constraint handler function:
-
retval
orsrc
is a null pointer -
dstsz
orlen
is greater than RSIZE_MAX/sizeof(wchar_t) (unlessdst
is null) -
dstsz
is not zero (unlessdst
is null) - There is no null character in the first
dstsz
multibyte characters in thesrc
array andlen
is greater thandstsz
(unlessdst
is null)
-
- As with all bounds-checked functions,
mbstowcs_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
In most implementations, mbstowcs
updates a global static object of type mbstate_t as it processes through the string, and cannot be called simultaneously by two threads, mbsrtowcs should be used in such cases.
POSIX specifies a common extension: if dst
is a null pointer, this function returns the number of wide characters that would be written to dst
, if converted. Similar behavior is standard for mbstowcs_s
and for mbsrtowcs.
Parameters
dst | - | pointer to wide character array where the wide string will be stored |
src | - | pointer to the first element of a null-terminated multibyte string to convert |
len | - | number of wide characters available in the array pointed to by dst |
dstsz | - | max number of wide characters that will be written (size of the dst array)
|
retval | - | pointer to a size_t object where the result will be stored |
Return value
1) On success, returns the number of wide characters, excluding the terminating L'\0', written to the destination array. On conversion error (if invalid multibyte character was encountered), returns (size_t)-1.
2) zero on success (in which case the number of wide characters excluding terminating zero that were, or would be written to
dst
, is stored in *retval), non-zero on error. In case of a runtime constraint violation, stores (size_t)-1 in *retval (unless retval
is null) and sets dst[0] to L'\0' (unless dst
is null or dstmax
is zero or greater than RSIZE_MAX)Example
Run this code
#include <stdio.h> #include <locale.h> #include <stdlib.h> #include <wchar.h> int main(void) { setlocale(LC_ALL, "en_US.utf8"); const char* mbstr = u8"z\u00df\u6c34\U0001F34C"; // or u8"zß水🍌" wchar_t wstr[5]; mbstowcs(wstr, mbstr, 5); wprintf(L"MB string: %s\n", mbstr); wprintf(L"Wide string: %ls\n", wstr); }
Output:
MB string: zß水🍌 Wide string: zß水🍌
References
- C11 standard (ISO/IEC 9899:2011):
- 7.22.8.1 The mbstowcs function (p: 359)
- K.3.6.5.1 The mbstowcs_s function (p: 611-612)
- C99 standard (ISO/IEC 9899:1999):
- 7.20.8.1 The mbstowcs function (p: 323)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.10.8.1 The mbstowcs function
See also
(C95)(C11) |
converts a narrow multibyte character string to wide string, given state (function) |
(C11) |
converts a wide string to narrow multibyte character string (function) |