const SysFunction SysFunction::functions[] =
		{"SIMILAR_TEXT", 1, 1, setParamsFromList, makeDoubleResult, evlSimilarText, NULL},
		
dsc* evlSimilarText(thread_db* tdbb, const SysFunction* function, const NestValueArray& args, impure_value* impure);

static inline size_t similar_str(const UChar *txt1, const size_t len1, const UChar *txt2, const size_t len2)
{
	size_t sum = 0, pos1 = 0, pos2 = 0, max = 0;
	UChar *p, *q;
	const UChar *end1 = (UChar *)txt1 + len1;
	const UChar *end2 = (UChar *)txt2 + len2;
	size_t l, l1, l2;
	UChar32 c1, c2;
	for (p = (UChar *)txt1; p < end1; p++) {
		for (q = (UChar *)txt2; q < end2; q++) {
			for (l = l1 = l2 = 0; (p + l1 < end1) && (q + l2 < end2);) {
				U16_NEXT(p, l1, len1, c1);
				U16_NEXT(q, l2, len2, c2);
				if (c1 == c2)
					l++;
				else
					break;
			}
			if (l > max) {
				max	= l;
				pos1 = p - txt1;
				pos2 = q - txt2;
			}
		}
	}
	if (max > 0) {
		sum = max;
		if ((pos1 + max < len1) && (pos2 + max < len2)) {
			sum += similar_str(txt1 + pos1 + max, len1 - pos1 - max,
							   txt2 + pos2 + max, len2 - pos2 - max);
		}
		if (pos1 && pos2) {
			sum += similar_str(txt1, pos1,
							   txt2, pos2);
		}
	}
	return sum;
}

dsc* evlSimilarText(thread_db* tdbb, const SysFunction* function, const NestValueArray& args,
	impure_value* impure)
{
	fb_assert(args.getCount() == 2);

	jrd_req* request = tdbb->getRequest();

	const dsc* str1 = EVL_expr(tdbb, request, args[0]);
	if (request->req_flags & req_null)	// return NULL if str1 is NULL
		return NULL;

	const dsc* str2 = EVL_expr(tdbb, request, args[1]);
	if (request->req_flags & req_null)	// return NULL if str2 is NULL
		return NULL;

	UCHAR* p1;
	MoveBuffer temp1;
	ULONG len1;
	len1 = MOV_make_string2(tdbb, str1, value->getCharSet(), &p1, temp1);

	UCHAR* p2;
	MoveBuffer temp2;
	ULONG len2;
	len2 = MOV_make_string2(tdbb, str2, value->getCharSet(), &p2, temp2);

	double rc;

	if (!len1 || !len2)
		rc = 0;
	else
		rc = similar_str(p1, len1, p2, len2) * 200.0 / (u_countChar32(p1, len1) + u_countChar32(p2, len2));

	impure->vlu_misc.vlu_double = rc;
	impure->vlu_desc.makeDouble(&impure->vlu_misc.vlu_double);

	return &impure->vlu_desc;
}