001/*-
002 * #%L
003 * HAPI FHIR - Master Data Management
004 * %%
005 * Copyright (C) 2014 - 2025 Smile CDR, Inc.
006 * %%
007 * Licensed under the Apache License, Version 2.0 (the "License");
008 * you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 *
011 *      http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 * #L%
019 */
020package ca.uhn.fhir.mdm.rules.matcher.util;
021
022import ca.uhn.fhir.mdm.rules.json.MdmFieldMatchJson;
023
024import java.util.List;
025
026public class MatchRuleUtil {
027        /**
028         * We use the binary shift operator (<<) to determine
029         * the "vector" used by
030         *
031         * By taking the log base 2 of a number N, we will know
032         * how many digits are needed to store N as binary.
033         * 1 more digit than that hits our overflow for a long value.
034         *
035         * ie, we cannot calculate vector values accurately after this,
036         * because we're hitting overflows and the << operator might lead
037         * to collisions or negative numbers that mean nothing.
038         *
039         * Note: by log rule -> log10(N) / log10(X) -> LogX(N)
040         */
041        public static long MAX_RULE_COUNT = Math.round(Math.log(Long.MAX_VALUE) / Math.log(2)) + 1;
042
043        public static boolean canHandleRuleCount(List<MdmFieldMatchJson> theRules) {
044                return theRules.size() <= MAX_RULE_COUNT;
045        }
046}