public member function

std::codecvt::length

<locale>
int length ( stateT& state, const externT* from, const externT* from_end, size_t max ) const;
Return length of translated sequence
Returns the amount of external characters in the range [from,from_end) that could be translated into at maximum max internal characters, as if done with codecvt::in.

state is also updated as if codecvt::in was called for a buffer of max internal characters.

During its operation, this function simply calls the virtual protected member codecvt::do_length, which is the member function in charge of performing the actions described above.

Parameters

state
State object to keep track of the state of a multibyte character conversion. Typically, this is an object of type mbstate_t.
stateT is the state type (i.e., the third template parameter of codecvt).
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.
externT is the external character type (i.e., the second template parameter of codecvt).
max
Maximum length of the translated sequence (in terms of internal characters).
size_t is an integral type.

Return value

The length of the sequence of characters if translated to internal characters.

Example

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// codecvt::length example
#include <iostream>
#include <locale>
using namespace std;

int main ()
{
  locale loc;
  mbstate_t mystate;
  char origin[] = "abcdefghijklmnopqrstuvwxyz";
  const char * pc;
  wchar_t * pwc;

  const codecvt<wchar_t,char,mbstate_t>& myfacet = 
    use_facet<codecvt<wchar_t,char,mbstate_t> >(loc);

  // calculate length for 10 wchar_t's:
  int length = myfacet.length (mystate, origin, origin+sizeof(origin), 10);

  wchar_t * dest = new wchar_t[length+1];
  myfacet.in (mystate, origin, origin+sizeof(origin), pc, dest, dest+length, pwc);

  dest[length]=0;  // Terminating null-character

  cout << "A string of 10 wchar_t elements: ";
  wcout << dest << endl;
  return 0;
}


Output:

A string of 10 wchar_t elements: abcdefghij

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)

C++