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std::strxfrm(3) 	       C++ Standard Libary		 std::strxfrm(3)

NAME
     std::strxfrm - std::strxfrm

Synopsis
	Defined in header <cstring>
	std::size_t strxfrm( char* dest, const char* src, std::size_t count );

	Transforms the null-terminated byte string pointed to by src into the
	implementation-defined	form such that comparing two transformed strings
     with
	std::strcmp gives the same result as comparing the original strings with
	std::strcoll, in the current C locale.

	The first count characters of the transformed string are written to des-
     tination,
	including the terminating null character, and the  length  of  the  full
     transformed
	string is returned, excluding the terminating null character.

	The behavior is undefined if the dest array is not large enough. The be-
     havior is
	undefined if dest and src overlap.

	If count is 0, then dest is allowed to be a null pointer.

Notes
	The correct length of the buffer that can receive the entire transformed
     string is 1
	+ std::strxfrm(nullptr, src, 0).

	This  function is used when making multiple locale-dependent comparisons
     using the
	same string or set of strings, because	it  is	more  efficient  to  use
     std::strxfrm to
	transform all the strings just once, and subsequently compare the trans-
     formed
	strings with std::strcmp.

Parameters
	dest   - pointer to the first element of the array where the transformed
     string will
		be written
	src   - pointer to the first character of a null-terminated byte  string
     to transform
	count - maximum number of characters to be written

Return value
	The  length  of  the  transformed  string, not including the terminating
     null-character.

Example
     // Run this code

      #include <cassert>
      #include <cstring>
      #include <iomanip>
      #include <iostream>
      #include <string>

      int main()
      {
	  char* loc = std::setlocale(LC_COLLATE, "cs_CZ.iso88592");
	  assert(loc);

	  std::string in1 = "hrnec";
	  std::string out1(1 + std::strxfrm(nullptr, in1.c_str(), 0), ' ');
	  std::string in2 = "chrt";
	  std::string out2(1 + std::strxfrm(nullptr, in2.c_str(), 0), ' ');

	  std::strxfrm(&out1[0], in1.c_str(), out1.size());
	  std::strxfrm(&out2[0], in2.c_str(), out2.size());

	  std::cout << "In the Czech locale: ";
	  if (out1 < out2)
	      std::cout << in1 << " before " << in2 << '\n';
	  else
	      std::cout << in2 << " before " << in1 << '\n';

	  std::cout << "In lexicographical comparison: ";
	  if (in1 < in2)
	      std::cout << in1 << " before " << in2 << '\n';
	  else
	      std::cout << in2 << " before " << in1 << '\n';
      }

Possible output:
      In the Czech locale: hrnec before chrt
      In lexicographical comparison: chrt before hrnec

See also
		     transform a wide string so that wcscmp  would  produce  the
     same result as
	wcsxfrm      wcscoll
		     (function)
	do_transform  transforms  a  string so that collation can be replaced by
     comparison
	[virtual]    (virtual protected member function of std::collate<CharT>)
	strcoll      compares two strings in accordance to the current locale
		     (function)
	C documentation for
	strxfrm

http://cppreference.com 	   2024.06.10			 std::strxfrm(3)
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