From cppreference.com
std::size_tstrxfrm(char*dest,constchar*src,std::size_tcount);Transforms the null-terminated byte string pointed to by src into the implementation-defined form such that comparing two transformed strings with
gives the same result as comparing the original strings with
, in the current C locale.
The first count characters of the transformed string are written to destination, 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 behavior 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
to transform all the strings just once, and subsequently compare the transformed strings with
.
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>intmain(){char*loc=std::setlocale(LC_COLLATE,"cs_CZ.iso88592");assert(loc);std::stringin1="hrnec";std::stringout1(1+std::strxfrm(nullptr,in1.c_str(),0),' ');std::stringin2="chrt";std::stringout2(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';elsestd::cout<<in2<<" before "<<in1<<'\n';std::cout<<"In lexicographical comparison: ";if(in1<in2)std::cout<<in1<<" before "<<in2<<'\n';elsestd::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 wcscoll
(function)
[virtual]
transforms a string so that collation can be replaced by comparison
(virtual protected member function of std::collate<CharT>)
compares two strings in accordance to the current locale
(function)