std::codecvt::length

Parameters

state

A state object, as required by the facet instantiation.
Typically, this is an object of type mbstate_t, able to keep track of the shift state of a multibyte character conversion.
Member type state_type is the facet's state type (defined as an alias of codecvt's third template parameter, stateT).

from, from_end

Pointer to the initial and final characters of the source sequence. The range used is [from,from_end), which contains all the characters between from and from_end, including the character pointed by from but not the character pointed by from_end.
Note that null characters are considered valid characters and do not stop the function from proceeding until from_end.
Member type extern_type is the facet's external character type (defined as an alias of codecvt's second template parameter, exnternT).

max

Maximum length of the translated sequence (in terms of internal characters).
size_t is an unsigned integral type.

Return value

Example

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// codecvt::length example
#include <iostream>       // std::wcout, std::endl
#include <locale>         // std::locale, std::codecvt, std::use_facet
#include <cwchar>         // std::mbstate_t
#include <cstddef>        // std::size_t
int main ()
{
  typedef std::codecvt<wchar_t,char,std::mbstate_t> facet_type;
  std::locale loc;
  const facet_type& myfacet = std::use_facet<facet_type>(loc);
  const char source[] = "abcdefghijklmnopqrstuvwxyz";
  // prepare objects for codecvt::length:
  std::mbstate_t mystate;
  const char * pc;
  wchar_t * pwc;
  // calculate length of dest (max 30):
  std::size_t length = myfacet.length (mystate, source, source+sizeof(source), 30);
  wchar_t* dest = new wchar_t[length];
  myfacet.in (mystate, source, source+sizeof(source), pc, dest, dest+length, pwc);
  std::wcout << dest << std::endl;
  delete[] dest;
  return 0;
}

abcdefghijklmnopqrstuvwxyz

Data races

Exception safety

See also

codecvt::in

Translate in characters (public member function)

codecvt::max_length

Return max length of one character (public member function)

codecvt::do_length

Return length of translated sequence [virtual] (public member function)