dylanhz commented on code in PR #20746: URL: https://github.com/apache/flink/pull/20746#discussion_r1684351449
########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/BaseConversionUtils.java: ########## @@ -0,0 +1,175 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.flink.table.runtime.functions; + +import java.util.Arrays; + +/** + * This is ported from Hive: org.apache.hadoop.hive.ql.udf.UDFConv.java. Just modify conv function + * return type to prevent codec overhead. + */ +public class BaseConversionUtils { + /** + * Divide x by m as if x is an unsigned 64-bit integer. Examples: unsignedLongDiv(-1, 2) == + * Long.MAX_VALUE unsignedLongDiv(6, 3) == 2 unsignedLongDiv(0, 5) == 0 + * + * @param x is treated as unsigned + * @param m is treated as signed + */ + private static long unsignedLongDiv(long x, int m) { + if (x >= 0) { + return x / m; + } + + // Let uval be the value of the unsigned long with the same bits as x + // Two's complement => x = uval - 2*MAX - 2 + // => uval = x + 2*MAX + 2 + // Now, use the fact: (a+b)/c = a/c + b/c + (a%c+b%c)/c + return x / m + + 2 * (Long.MAX_VALUE / m) + + 2 / m + + (x % m + 2 * (Long.MAX_VALUE % m) + 2 % m) / m; + } + + /** + * Decode val into value[]. + * + * @param val is treated as an unsigned 64-bit integer + * @param radix must be between MIN_RADIX and MAX_RADIX + */ + private static void decode(byte[] value, long val, int radix) { + Arrays.fill(value, (byte) 0); + for (int i = value.length - 1; val != 0; i--) { + long q = unsignedLongDiv(val, radix); + value[i] = (byte) (val - q * radix); + val = q; + } + } + + /** + * Convert value[] into a long. On overflow, return -1 (as mySQL does). If a negative digit is + * found, ignore the suffix starting there. + * + * @param radix must be between MIN_RADIX and MAX_RADIX + * @param fromPos is the first element that should be conisdered + * @return the result should be treated as an unsigned 64-bit integer. + */ + private static long encode(byte[] value, int radix, int fromPos) { + long val = 0; + long bound = unsignedLongDiv(-1 - radix, radix); // Possible overflow once + // val + // exceeds this value + for (int i = fromPos; i < value.length && value[i] >= 0; i++) { + if (val >= bound) { + // Check for overflow + if (unsignedLongDiv(-1 - value[i], radix) < val) { + return -1; + } + } + val = val * radix + value[i]; + } + return val; + } + + /** + * Convert the bytes in value[] to the corresponding chars. + * + * @param radix must be between MIN_RADIX and MAX_RADIX + * @param fromPos is the first nonzero element + */ + private static void byte2char(byte[] value, int radix, int fromPos) { + for (int i = fromPos; i < value.length; i++) { + value[i] = (byte) Character.toUpperCase(Character.forDigit(value[i], radix)); + } + } + + /** + * Convert the chars in value[] to the corresponding integers. Convert invalid characters to -1. + * + * @param radix must be between MIN_RADIX and MAX_RADIX + * @param fromPos is the first nonzero element + */ + private static boolean char2byte(byte[] value, int radix, int fromPos) { + for (int i = fromPos; i < value.length; i++) { + value[i] = (byte) Character.digit(value[i], radix); + if (value[i] == -1) { + return false; + } + } + return true; + } + + /** + * Convert numbers between different number bases. If toBase>0 the result is unsigned, + * otherwise it is signed. + */ + public static byte[] conv(byte[] n, int fromBase, int toBase) { + byte[] value = new byte[64]; + if (n == null || n.length < 1) { + return null; + } + + if (fromBase < Character.MIN_RADIX + || fromBase > Character.MAX_RADIX + || Math.abs(toBase) < Character.MIN_RADIX + || Math.abs(toBase) > Character.MAX_RADIX) { + return null; + } + + boolean negative = (n[0] == '-'); + int first = 0; + if (negative) { + first = 1; + } + + // Copy the digits in the right side of the array + for (int i = 1; i <= n.length - first; i++) { + value[value.length - i] = n[n.length - i]; + } + if (!char2byte(value, fromBase, value.length - n.length + first)) { + return null; + } + + // Do the conversion by going through a 64 bit integer + long val = encode(value, fromBase, value.length - n.length + first); + if (negative && toBase > 0) { + if (val < 0) { + val = -1; + } else { + val = -val; + } + } + if (toBase < 0 && val < 0) { + val = -val; + negative = true; + } Review Comment: Hello, I'm currently working on this function. I find the logic of the code from lines 151 to 161 very strange, which is the same as hive and spark, do you have any insights on it? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@flink.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
