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wcslen, wcsnlen_s - cppreference.com

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Defined in header <wchar.h>

size_t wcslen( const wchar_t *str );

 (1) (since C95)

size_t wcsnlen_s(const wchar_t *str, size_t strsz);

 (2) (since C11)

1) Returns the length of a wide string, that is the number of non-null wide characters that precede the terminating null wide character.

2) Same as (1), except that the function returns zero if str is a null pointer and returns strsz if the null wide character was not found in the first strsz wide characters of src

As with all bounds-checked functions, wcslen_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 including <stdio.h>..

Parameters

str - pointer to the null-terminated wide string to be examined
strsz - maximum number of wide characters to examine

Return value

1) The length of the null-terminated wide string str.

2) The length of the null-terminated wide string str on success, zero if str is a null pointer, strsz if the null wide character was not found.

Notes

strnlen_s and wcsnlen_s are the only bounds-checked functions that do not invoke the runtime constraints handler. They are pure utility functions used to provide limited support for non-null terminated strings.

Example

#include <wchar.h>
#include <stdio.h>

int main(void)
{
    wchar_t str[] = L"How many wide characters does this string contain?";

    printf("without null character: %zu\n", wcslen(str));
    printf("with null character: %zu\n", sizeof str / sizeof *str);
}

Output: 

without null character: 50
with null character: 51

References

  • C11 standard (ISO/IEC 9899:2011):
  • 7.29.4.6.1 The wcslen function (p: 439)
  • K.3.9.2.4.1 The wcsnlen_s function (p: 646-647)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.24.4.6.1 The wcslen function (p: 385)

See also