root/src/common/tuklib_mbstr_width.c

DEFINITIONS

1. tuklib_mbstr_width

///////////////////////////////////////////////////////////////////////////////
//
/// \file       tuklib_mstr_width.c
/// \brief      Calculate width of a multibyte string
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "tuklib_mbstr.h"

#if defined(HAVE_MBRTOWC) && defined(HAVE_WCWIDTH)
#       include <wchar.h>
#endif


extern size_t
tuklib_mbstr_width(const char *str, size_t *bytes)
{
        const size_t len = strlen(str);
        if (bytes != NULL)
                *bytes = len;

#if !(defined(HAVE_MBRTOWC) && defined(HAVE_WCWIDTH))
        // In single-byte mode, the width of the string is the same
        // as its length.
        return len;

#else
        mbstate_t state;
        memset(&state, 0, sizeof(state));

        size_t width = 0;
        size_t i = 0;

        // Convert one multibyte character at a time to wchar_t
        // and get its width using wcwidth().
        while (i < len) {
                wchar_t wc;
                const size_t ret = mbrtowc(&wc, str + i, len - i, &state);
                if (ret < 1 || ret > len)
                        return (size_t)-1;

                i += ret;

                const int wc_width = wcwidth(wc);
                if (wc_width < 0)
                        return (size_t)-1;

                width += wc_width;
        }

        // Require that the string ends in the initial shift state.
        // This way the caller can be combine the string with other
        // strings without needing to worry about the shift states.
        if (!mbsinit(&state))
                return (size_t)-1;

        return width;
#endif
}