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/*

FUNCTION

        <<wcswidth>>---number of column positions of a wide-character string

INDEX

        wcswidth

ANSI_SYNOPSIS

        #include <wchar.h>

        int wcswidth(const wchar_t *<[pwcs]>, size_t <[n]>);

TRAD_SYNOPSIS

        #include <wchar.h>

        int wcswidth(<[pwcs]>, <[n]>)

        wchar_t *<[wc]>;

        size_t <[n]>;

DESCRIPTION

        The <<wcswidth>> function shall determine the number of column

        positions required for <[n]> wide-character codes (or fewer than <[n]>

        wide-character codes if a null wide-character code is encountered

        before <[n]> wide-character codes are exhausted) in the string pointed

        to by <[pwcs]>.

RETURNS

        The <<wcswidth>> function either shall return 0 (if <[pwcs]> points to a

        null wide-character code), or return the number of column positions

        to be occupied by the wide-character string pointed to by <[pwcs]>, or

        return -1 (if any of the first <[n]> wide-character codes in the

        wide-character string pointed to by <[pwcs]> is not a printable

        wide-character code).

PORTABILITY

<<wcswidth>> has been introduced in the Single UNIX Specification Volume 2.

<<wcswidth>> has been marked as an extension in the Single UNIX Specification Volume 3.

*/

#include <_ansi.h>

#include <wchar.h>

#include "local.h"

int

_DEFUN (wcswidth, (pwcs, n),

        _CONST wchar_t *pwcs _AND

        size_t n)

{

  int w, len = 0;

  if (!pwcs || n == 0)

    return 0;

  do {

    wint_t wi = *pwcs;

#ifdef _MB_CAPABLE

  wi = _jp2uc (wi);

  /* First half of a surrogate pair? */

  if (sizeof (wchar_t) == 2 && wi >= 0xd800 && wi <= 0xdbff)

    {

      wint_t wi2;

      /* Extract second half and check for validity. */

      if (--n == 0 || (wi2 = _jp2uc (*++pwcs)) < 0xdc00 || wi2 > 0xdfff)

        return -1;

      /* Compute actual unicode value to use in call to __wcwidth. */

      wi = (((wi & 0x3ff) << 10) | (wi2 & 0x3ff)) + 0x10000;

    }

#endif /* _MB_CAPABLE */

    if ((w = __wcwidth (wi)) < 0)

      return -1;

    len += w;

  } while (*pwcs++ && --n > 0);

  return len;

}