wcsxfrm(3)wcsxfrm(3)NAMEwcsxfrm - Transform wide-character strings for collation in the current
locale
SYNOPSIS
#include <wchar.h>
size_t wcsxfrm(
wchar_t *ws1,
const wchar_t *ws2,
size_t n );
LIBRARY
Standard C Library (libc)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
wcsxfrm(): XSH5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Contains a pointer to the destination wide-character string. Contains
a pointer to the source wide-character string. Specifies the maximum
number of wide-character codes to place into the array specified by
ws1.
DESCRIPTION
The wcsxfrm() function is used to transform the wide-character string
specified by the ws2 parameter into a string of wide-character codes
based on the collation values of the wide characters in the current
setting of the LC_COLLATE locale category. No more than n wide charac‐
ters (including the terminating null wide character) are copied into
the array specified by the ws1 parameter. When two transformed wide-
character strings are obtained and the transformed strings are compared
using wcscmp(), the result is the same as that obtained by a direct
call to wcscoll() on the two original wide-character strings.
The application can call wcsxfrm() with ws1 as a null pointer to deter‐
mine the number of wide characters to allocate for the ws1 parameter.
For example, the following expression calculates the size of ws1:
1 + wcsxfrm(NULL, ws2, 0)
As shown in this example, the n parameter must be 0 (zero) when ws1 is
a null pointer.
When operating on overlapping strings, the behavior of the wcsxfrm()
function is unreliable.
NOTES
If an application does multiple comparisons based on the current
locale's collation values and uses the same set of text strings, the
wcsxfrm() transformation function in conjunction with the wcscmp()
function may be more efficient than the wcscoll() collation function.
This is because the string is transformed based on the locale tables
only once. However, the transformation function must convert all char‐
acters in the string for each level of a multilevel collation. In com‐
parison, the collation function stops comparing characters at the first
inequality. These tradeoffs make the most efficient method for a spe‐
cific application dependent on the number of repeated comparisons of
strings within the set, the number of collation levels for the current
locale, and the values of the strings within the set.
RETURN VALUES
If the ws1 parameter is a wide-character null pointer, the wcsxfrm()
function returns the number of wide-character elements (not including
the terminating null wide character) required to store the transformed
wide-character string. If the count specified by the n parameter is
sufficient to hold the transformed string in the ws1 parameter (includ‐
ing the terminating null wide character) the return value is set to the
actual number of wide-character elements placed in the ws1 parameter,
not including the terminating null wide character. If the return value
is equal to or greater than the value specified by the n parameter, the
contents of the array pointed to by the ws1 parameter are indetermi‐
nate.
On error, the wcsxfrm() function returns (size_t)-1 and sets errno to
indicate the error.
ERRORS
If any the following conditions occur, the wcsxfrm() function sets
errno to the corresponding value: The ws2 parameter contains wide-char‐
acter codes outside the domain of the collating sequence defined by the
current locale. [Tru64 UNIX] There was insufficient memory available
to allocate temporary storage for this operation.
SEE ALSO
Functions: setlocale(3), string(3), wcscmp(3), wcscoll(3)
Standards: standards(5)wcsxfrm(3)
