tuklib_mbstr_width.c File Reference

Calculate width of a multibyte string. More...

#include "tuklib_mbstr.h"
#include <string.h>

Go to the source code of this file.

Functions
size_t	tuklib_mbstr_width (const char *str, size_t *bytes)
	Get the number of columns needed for the multibyte string. More...

Detailed Description

Calculate width of a multibyte string.

Definition in file tuklib_mbstr_width.c.

Function Documentation

tuklib_mbstr_width()

size_t tuklib_mbstr_width	(	const char *	str,
		size_t *	bytes
	)

Get the number of columns needed for the multibyte string.

This is somewhat similar to wcswidth() but works on multibyte strings.

Parameters

str	String whose width is to be calculated. If the current locale uses a multibyte character set that has shift states, the string must begin and end in the initial shift state.
bytes	If this is not NULL, *bytes is set to the value returned by strlen(str) (even if an error occurs when calculating the width).

Returns

On success, the number of columns needed to display the string e.g. in a terminal emulator is returned. On error, (size_t)-1 is returned. Possible errors include invalid, partial, or non-printable multibyte character in str, or that str doesn't end in the initial shift state.

Definition at line 22 of file tuklib_mbstr_width.c.

{
    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
}

References bytes, i, len, memset(), NULL, cmd_descs_generate::str, and width.