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Defined in header <wchar.h> | ||
| (1) | ||
wchar_t* wcsncpy(wchar_t* dest,constwchar_t* src,size_t count); | (since C95) (until C99) | |
wchar_t*wcsncpy(wchar_t*restrict dest,constwchar_t*restrict src,size_t count); | (since C99) | |
errno_t wcsncpy_s(wchar_t*restrict dest, rsize_t destsz, constwchar_t*restrict src, rsize_t count); | (2) | (since C11) |
count characters of the wide string pointed to bysrc (including the terminating null wide character) to wide character array pointed to bydest.count is reached before the entire stringsrc was copied, the resulting wide character array is not null-terminated.src,count is not reached, additional null wide characters are written todest until the total ofcount characters have been written.count, it stops after writing the terminating null character (if there was no null in the source, it writes one atdest[count] and then stops). Also, the following errors are detected at runtime and call the currently installedconstraint handler function:src ordest is a null pointerdestsz orcount is zero or greater thanRSIZE_MAX/sizeof(wchar_t)count is greater or equaldestsz, butdestsz is less or equalwcsnlen_s(src, count), in other words, truncation would occurwcsncpy_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 constant1 before including<wchar.h>.Contents |
| dest | - | pointer to the wide character array to copy to |
| src | - | pointer to the wide string to copy from |
| count | - | maximum number of wide characters to copy |
| destsz | - | the size of the destination buffer |
destdest is a null pointer ordestsz is zero or greater thanRSIZE_MAX/sizeof(wchar_t)) and may clobber the rest of the destination array with unspecified values.In typical usage,count is the number of elements in the destination array.
Although truncation to fit the destination buffer is a security risk and therefore a runtime constraints violation forwcsncpy_s, it is possible to get the truncating behavior by specifyingcount equal to the size of the destination array minus one: it will copy the firstcount wide characters and append the null wide terminator as always:wcsncpy_s(dst,sizeof dst/sizeof*dst, src,(sizeof dst/sizeof*dst)-1);
#include <stdio.h>#include <wchar.h>#include <locale.h> int main(void){constwchar_t src[]= L"わゐ";wchar_t dest[6]={L'あ', L'い', L'う', L'え', L'お'}; wcsncpy(dest, src,4);// this will copy わゐ and repeat L'\0' two times puts("The contents of dest are: ");setlocale(LC_ALL,"en_US.utf8"); constlong dest_size=sizeof dest/sizeof*dest;for(wchar_t* p= dest; p-dest!= dest_size;++p){*p?printf("%lc ",*p):printf("\\0 ");}}
Possible output:
The contents of dest are: わ ゐ \0 \0 お \0
(C95)(C11) | copies one wide string to another (function)[edit] |
(C95)(C11) | copies a certain amount of wide characters between two non-overlapping arrays (function)[edit] |
(C11) | copies a certain amount of characters from one string to another (function)[edit] |
C++ documentation forwcsncpy | |
