mbsrtowcs, mbsrtowcs_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 null-terminated multibyte character sequence, which begins in the conversion state described by
*ps
, from the array whose first element is pointed to by *src to its wide character representation. If dst
is not null, converted characters are stored in the successive elements of the wchar_t array pointed to by dst
. No more than len
wide characters are written to the destination array. Each multibyte character is converted as if by a call to mbrtowc. The conversion stops if:
- The multibyte null character was converted and stored. *src is set to null pointer value and
*ps
represents the initial shift state. - An invalid multibyte character (according to the current C locale) was encountered. *src is set to point at the beginning of the first unconverted multibyte character.
- the next wide character to be stored would exceed
len
. *src is set to point at the beginning of the first unconverted multibyte 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 no null character was written to
dst
afterlen
wide characters were written, then L'\0' is stored indst[len]
, which means len+1 total wide characters are written - 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/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 the *src array andlen
is greater thandstsz
(unlessdst
is null)
-
- As with all bounds-checked functions,
mbsrtowcs_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 includingwchar.h
.
Parameters
dst | - | pointer to wide character array where the results will be stored |
src | - | pointer to pointer to the first element of a null-terminated multibyte string |
len | - | number of wide characters available in the array pointed to by dst |
ps | - | pointer to the conversion state object |
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 character array. If
dst
is a null pointer, returns the number of wide characters that would have been written given unlimited length. On conversion error (if invalid multibyte character was encountered), returns (size_t)-1, stores EILSEQ in errno, and leaves *ps in unspecified state.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-sero 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 <wchar.h> #include <string.h> void print_as_wide(const char* mbstr) { mbstate_t state; memset(&state, 0, sizeof state); size_t len = 1 + mbsrtowcs(NULL, &mbstr, 0, &state); wchar_t wstr[len]; mbsrtowcs(&wstr[0], &mbstr, len, &state); wprintf(L"Wide string: %ls \n", wstr); wprintf(L"The length, including L'\\0': %zu\n", len); } int main(void) { setlocale(LC_ALL, "en_US.utf8"); print_as_wide(u8"z\u00df\u6c34\U0001f34c"); // u8"zß水🍌" }
Output:
Wide string: zß水🍌 The length, including L'\0': 5
References
- C11 standard (ISO/IEC 9899:2011):
- 7.29.6.4.1 The mbsrtowcs function (p: 445)
- K.3.9.3.2.1 The mbsrtowcs_s function (p: 648-649)
- C99 standard (ISO/IEC 9899:1999):
- 7.24.6.4.1 The mbsrtowcs function (p: 391)
See also
(C11) |
converts a narrow multibyte character string to wide string (function) |
(C95) |
converts the next multibyte character to wide character, given state (function) |
(C95)(C11) |
converts a wide string to narrow multibyte character string, given state (function) |