newlib/libc/string/wcswidth.c

   1 /*
   2 FUNCTION
   3         <<wcswidth>>---number of column positions of a wide-character string
   4
   5 INDEX
   6         wcswidth
   7
   8 SYNOPSIS
   9         #include <wchar.h>
  10         int wcswidth(const wchar_t *<[pwcs]>, size_t <[n]>);
  11
  12 DESCRIPTION
  13         The <<wcswidth>> function shall determine the number of column
  14         positions required for <[n]> wide-character codes (or fewer than <[n]>
  15         wide-character codes if a null wide-character code is encountered
  16         before <[n]> wide-character codes are exhausted) in the string pointed
  17         to by <[pwcs]>.
  18
  19 RETURNS
  20         The <<wcswidth>> function either shall return 0 (if <[pwcs]> points to a
  21         null wide-character code), or return the number of column positions
  22         to be occupied by the wide-character string pointed to by <[pwcs]>, or
  23         return -1 (if any of the first <[n]> wide-character codes in the
  24         wide-character string pointed to by <[pwcs]> is not a printable
  25         wide-character code).
  26
  27 PORTABILITY
  28 <<wcswidth>> has been introduced in the Single UNIX Specification Volume 2.
  29 <<wcswidth>> has been marked as an extension in the Single UNIX Specification Volume 3.
  30 */
  31
  32 #include <_ansi.h>
  33 #include <wchar.h>
  34 #include "local.h"
  35
  36 int
  37 wcswidth (const wchar_t *pwcs,
  38         size_t n)
  39
  40 {
  41   int w, len = 0;
  42   if (!pwcs || n == 0)
  43     return 0;
  44   do {
  45     wint_t wi = *pwcs;
  46
  47 #ifdef _MB_CAPABLE
  48   wi = _jp2uc (wi);
  49   /* First half of a surrogate pair? */
  50   if (sizeof (wchar_t) == 2 && wi >= 0xd800 && wi <= 0xdbff)
  51     {
  52       wint_t wi2;
  53
  54       /* Extract second half and check for validity. */
  55       if (--n == 0 || (wi2 = _jp2uc (*++pwcs)) < 0xdc00 || wi2 > 0xdfff)
  56         return -1;
  57       /* Compute actual unicode value to use in call to __wcwidth. */
  58       wi = (((wi & 0x3ff) << 10) | (wi2 & 0x3ff)) + 0x10000;
  59     }
  60 #endif /* _MB_CAPABLE */
  61     if ((w = __wcwidth (wi)) < 0)
  62       return -1;
  63     len += w;
  64   } while (*pwcs++ && --n > 0);
  65   return len;
  66 }