src/common/tuklib_mbstr_width.c

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