wcsrtombs, wcsrtombs_s
From cppreference.com
Defined in header <wchar.h>
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(1) | ||
(since C95) (until C99) |
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(since C99) | ||
(2) | (since C11) | |
1) Converts a sequence of wide characters from the array whose first element is pointed to by *src to its narrow multibyte representation that begins in the conversion state described by *ps. If
dst
is not null, converted characters are stored in the successive elements of the char array pointed to by dst
. No more than len
bytes are written to the destination array. Each character is converted as if by a call to wcrtomb. The conversion stops if:
- The null character L'\0' was converted and stored. The bytes stored in this case are the unshift sequence (if necessary) followed by '\0', *src is set to null pointer value and *ps represents the initial shift state.
- A wchar_t was found that does not correspond to a valid character in the current C locale. *src is set to point at the first unconverted wide character.
- the next multibyte character to be stored would exceed
len
. *src is set to point at the first unconverted wide character. This condition is not checked ifdst
is a null pointer.
2) Same as (1), except that
- the function returns its result as an out-parameter
retval
- if the conversion stops without writing a null character, the function will store '\0' in the next byte in
dst
, which may be dst[len] or dst[dstsz], whichever comes first (meaning up to len+1/dstsz+1 total bytes may be written). In this case, there may be no unshift sequence written before the terminating null. - the function clobbers the destination array from the terminating null and until
dstsz
- If
src
anddst
overlap, the behavior is unspecified. - the following errors are detected at runtime and call the currently installed constraint handler function:
-
retval
,ps
,src
, or *src is a null pointer -
dstsz
orlen
is greater than RSIZE_MAX (unlessdst
is null) -
dstsz
is not zero (unlessdst
is null) -
len
is greater thandstsz
and the conversion does not encounter null or encoding error in thesrc
array by the timedstsz
is reached (unlessdst
is null)
-
- As with all bounds-checked functions,
wcsrtombs_s
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 <wchar.h>.
Parameters
dst | - | pointer to narrow character array where the multibyte characters will be stored |
src | - | pointer to pointer to the first element of a null-terminated wide string |
len | - | number of bytes available in the array pointed to by dst |
ps | - | pointer to the conversion state object |
dstsz | - | max number of bytes 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 bytes (including any shift sequences, but excluding the terminating '\0') written to the character array whose first element is pointed to by
dst
. If dst
is a null pointer, returns the number of bytes that would have been written. On conversion error (if invalid wide character was encountered), returns (size_t)-1, stores EILSEQ in errno, and leaves *ps in unspecified state.2) Returns zero on success (in which case the number of bytes 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 '\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 <string.h> #include <wchar.h> void print_wide(const wchar_t* wstr) { mbstate_t state; memset(&state, 0, sizeof state); size_t len = 1 + wcsrtombs(NULL, &wstr, 0, &state); char mbstr[len]; wcsrtombs(mbstr, &wstr, len, &state); printf("Multibyte string: %s\n", mbstr); printf("Length, including '\\0': %zu\n", len); } int main(void) { setlocale(LC_ALL, "en_US.utf8"); print_wide(L"z\u00df\u6c34\U0001f34c"); // or L"zß水🍌" }
Output:
Multibyte string: zß水🍌 Length, including '\0': 11
References
- C17 standard (ISO/IEC 9899:2018):
- 7.29.6.4.2 The wcsrtombs function (p: 324-325)
- K.3.9.3.2.2 The wcsrtombs_s function (p: 471-472)
- C11 standard (ISO/IEC 9899:2011):
- 7.29.6.4.2 The wcsrtombs function (p: 446)
- K.3.9.3.2.2 The wcsrtombs_s function (p: 649-651)
- C99 standard (ISO/IEC 9899:1999):
- 7.24.6.4.2 The wcsrtombs function (p: 392)
See also
(C11) |
converts a wide string to narrow multibyte character string (function) |
(C95)(C11) |
converts a wide character to its multibyte representation, given state (function) |
(C95)(C11) |
converts a narrow multibyte character string to wide string, given state (function) |