src/common/tuklib_mbstr_width.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       tuklib_mbstr_width.c
   4 /// \brief      Calculate width of a multibyte string
   5 //
   6 //  Author:     Lasse Collin
   7 //
   8 //  This file has been put into the public domain.
   9 //  You can do whatever you want with this file.
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "tuklib_mbstr.h"
  14 #include <string.h>
  15
  16 #if defined(HAVE_MBRTOWC) && defined(HAVE_WCWIDTH)
  17 #       include <wchar.h>
  18 #endif
  19
  20
  21 extern size_t
  22 tuklib_mbstr_width(const char *str, size_t *bytes)
  23 {
  24         const size_t len = strlen(str);
  25         if (bytes != NULL)
  26                 *bytes = len;
  27
  28 #if !(defined(HAVE_MBRTOWC) && defined(HAVE_WCWIDTH))
  29         // In single-byte mode, the width of the string is the same
  30         // as its length.
  31         return len;
  32
  33 #else
  34         mbstate_t state;
  35         memset(&state, 0, sizeof(state));
  36
  37         size_t width = 0;
  38         size_t i = 0;
  39
  40         // Convert one multibyte character at a time to wchar_t
  41         // and get its width using wcwidth().
  42         while (i < len) {
  43                 wchar_t wc;
  44                 const size_t ret = mbrtowc(&wc, str + i, len - i, &state);
  45                 if (ret < 1 || ret > len)
  46                         return (size_t)-1;
  47
  48                 i += ret;
  49
  50                 const int wc_width = wcwidth(wc);
  51                 if (wc_width < 0)
  52                         return (size_t)-1;
  53
  54                 width += (size_t)wc_width;
  55         }
  56
  57         // Require that the string ends in the initial shift state.
  58         // This way the caller can be combine the string with other
  59         // strings without needing to worry about the shift states.
  60         if (!mbsinit(&state))
  61                 return (size_t)-1;
  62
  63         return width;
  64 #endif
  65 }