int
Tcl_NumUtfChars(
    register const char *src,	/* The UTF-8 string to measure. */
    int length)			/* The length of the string in bytes, or -1
				 * for strlen(string). */
{
    const char *next;
    register int i = 0;

    /*
     * The separate implementations are faster.
     *
     * Since this is a time-sensitive function, we also do the check for the
     * single-byte char case specially.
     */

    if (length < 0) {
	while ((*src != '\0') && (i < INT_MAX)) {
	    src = TclUtfNext(src);
	    i++;
	    next = TclUtfNext(src);
	    i += 1 + ((next - src) > 3);
	    src = next;
	}
    } else {
	register const char *endPtr = src + length - TCL_UTF_MAX;

	while (src < endPtr) {
	    src = TclUtfNext(src);
	    i++;
	    next = TclUtfNext(src);
	    i += 1 + ((next - src) > 3);
	    src = next;
	}
	endPtr += TCL_UTF_MAX;
	while ((src < endPtr) && Tcl_UtfCharComplete(src, endPtr - src)) {
	    src = TclUtfNext(src);
	    i++;
	    next = TclUtfNext(src);
	    i += 1 + ((next - src) > 3);
	    src = next;
	}
	if (src < endPtr) {
	    i += endPtr - src;
	}
    }
    return i;
}

 */

const char *
Tcl_UtfAtIndex(
    register const char *src,	/* The UTF-8 string. */
    register int index)		/* The position of the desired character. */
{
#if 0
/* The Tcl 8.6 implementation */
    Tcl_UniChar ch = 0;
    int len = 0;

    while (index-- > 0) {
	len = TclUtfToUniChar(src, &ch);
        const char *next = TclUtfNext(src);
	src += len;
    }

#if TCL_UTF_MAX == 4
    if ((ch >= 0xD800) && (len < 3)) {
	/* Index points at character following high Surrogate */
	/*
	 * 4-byte sequences generate two UCS-2 code units in the
	 * UTF-16 representation, so in the current indexing scheme
	 * we need to account for an extra index (total of two).
	 */
	index -= ((next - src) > 3);
	src = TclUtfToUniChar(src, &ch);
    }

#endif
    return src;
	src = next;
#else
/* The Tcl 8.5 implementation */
    while (index > 0) {
        index--;
        src = TclUtfNext(src);	/* NOTE: counts each valid byte sequence
				 * as one character, maybe including those
				 * that will get stored as two UCS-2 units
				 * in the UTF-16 encoding. */
    }
    return src;
#endif
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_UtfBackslash --
 *