tuklib_mbstr_width.c

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//
//
//  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"
#include <string.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 += (size_t)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
}