Java tutorial
/* * 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 com.easemob.dataexport.utils; import java.util.Collections; import java.util.List; import java.util.Random; import java.util.UUID; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.locks.ReentrantLock; import com.fasterxml.uuid.EthernetAddress; import com.fasterxml.uuid.UUIDComparator; import static com.fasterxml.uuid.impl.UUIDUtil.BYTE_OFFSET_CLOCK_HI; import static com.fasterxml.uuid.impl.UUIDUtil.BYTE_OFFSET_CLOCK_LO; import static com.fasterxml.uuid.impl.UUIDUtil.BYTE_OFFSET_CLOCK_MID; import static com.fasterxml.uuid.impl.UUIDUtil.BYTE_OFFSET_CLOCK_SEQUENCE; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import static org.apache.commons.codec.binary.Base64.decodeBase64; import static org.apache.commons.codec.binary.Base64.encodeBase64URLSafeString; import static com.easemob.dataexport.utils.ConversionUtils.bytes; import static com.easemob.dataexport.utils.ConversionUtils.uuid; public class UUIDUtils { private static final Logger LOG = LoggerFactory.getLogger(UUIDUtils.class); private static final int[] MICROS = new int[1000]; static { for (int x = 0; x < 1000; x++) { MICROS[x] = x * 10; } } private static ReentrantLock tsLock = new ReentrantLock(true); public static final UUID MIN_TIME_UUID = UUID.fromString("00000000-0000-1000-8000-000000000000"); public static final UUID MAX_TIME_UUID = UUID.fromString("ffffffff-ffff-1fff-bfff-ffffffffffff"); public static final UUID ZERO_UUID = new UUID(0, 0); private static long timestampMillisNow = System.currentTimeMillis(); private static AtomicInteger currentMicrosPoint = new AtomicInteger(0); private static AtomicInteger customMicrosPointer = new AtomicInteger(0); public static final UUIDComparator UUID_COMPARATOR = new UUIDComparator(); /** * Return the "next" UUID in micro second resolution. <b>WARNING</b>: this is designed to return the next unique * timestamped UUID for this JVM. Depending on velocity of the call, this method may block internally to insure that * "now" is kept in sync with the UUIDs being generated by this call. * <p/> * In other words, we will intentionally burn CPU insuring that this method is not executed more than 10k -1 times * per millisecond and guarantee that those microseconds held within are sequential. * <p/> * If we did not do this, you would get <b>timestamp collision</b> even though the UUIDs will technically be * 'unique.' */ public static java.util.UUID newTimeUUID() { // get & inc counter, but roll on 1k (because we divide by 10 on retrieval) // if count + currentMicro > 1k, block and roll tsLock.lock(); long ts = System.currentTimeMillis(); if (ts > timestampMillisNow) { timestampMillisNow = ts; currentMicrosPoint.set(0); } int pointer = currentMicrosPoint.getAndIncrement(); try { if (pointer > 990) { TimeUnit.MILLISECONDS.sleep(1L); } } catch (Exception ex) { ex.printStackTrace(); } finally { tsLock.unlock(); } return newTimeUUID(ts, MICROS[pointer]); } private static final long KCLOCK_OFFSET = 0x01b21dd213814000L; private static final long KCLOCK_MULTIPLIER_L = 10000L; private static final Random CLOCK_SEQ_RANDOM = new Random(); // 14 bits of randomness private static int getRandomClockSequence() { return CLOCK_SEQ_RANDOM.nextInt() & 0x3FFF; } private static void setTimestamp(long timestamp, byte[] uuidBytes, int clockSeq, int timeOffset) { timestamp *= KCLOCK_MULTIPLIER_L; timestamp += KCLOCK_OFFSET; timestamp += timeOffset; // Set random clock sequence uuidBytes[BYTE_OFFSET_CLOCK_SEQUENCE] = (byte) (clockSeq >> 8); uuidBytes[BYTE_OFFSET_CLOCK_SEQUENCE + 1] = (byte) clockSeq; // Set variant uuidBytes[BYTE_OFFSET_CLOCK_SEQUENCE] &= 0x3F; uuidBytes[BYTE_OFFSET_CLOCK_SEQUENCE] |= 0x80; setTime(uuidBytes, timestamp); } @SuppressWarnings("all") private static void setTime(byte[] uuidBytes, long timestamp) { // Time fields aren't nicely split across the UUID, so can't just // linearly dump the stamp: int clockHi = (int) (timestamp >>> 32); int clockLo = (int) timestamp; uuidBytes[BYTE_OFFSET_CLOCK_HI] = (byte) (clockHi >>> 24); uuidBytes[BYTE_OFFSET_CLOCK_HI + 1] = (byte) (clockHi >>> 16); uuidBytes[BYTE_OFFSET_CLOCK_MID] = (byte) (clockHi >>> 8); uuidBytes[BYTE_OFFSET_CLOCK_MID + 1] = (byte) clockHi; uuidBytes[BYTE_OFFSET_CLOCK_LO] = (byte) (clockLo >>> 24); uuidBytes[BYTE_OFFSET_CLOCK_LO + 1] = (byte) (clockLo >>> 16); uuidBytes[BYTE_OFFSET_CLOCK_LO + 2] = (byte) (clockLo >>> 8); uuidBytes[BYTE_OFFSET_CLOCK_LO + 3] = (byte) clockLo; // Set version uuidBytes[BYTE_OFFSET_CLOCK_HI] &= 0x0F; uuidBytes[BYTE_OFFSET_CLOCK_HI] |= 0x10; } /** * Generate a timeuuid with the given timestamp in milliseconds and the time offset. Useful when you need to * generate sequential UUIDs for the same period in time. I.E * <p/> * newTimeUUID(1000, 0) <br/> newTimeUUID(1000, 1) <br /> newTimeUUID(1000, 2) <br /> * <p/> * etc. * <p/> * Only use this method if you are absolutely sure you need it. When it doubt use the method without the timestamp * offset * * @param ts The timestamp in milliseconds * @param timeoffset The offset, which should always be <= 10000. If you go beyond this range, the millisecond will * be incremented since this is beyond the possible values when coverrting from millis to 1/10 microseconds stored * in the time uuid. */ public static UUID newTimeUUID(long ts, int timeoffset) { if (ts == 0) { return newTimeUUID(); } byte[] uuidBytes = new byte[16]; // 47 bits of randomness EthernetAddress eth = EthernetAddress.constructMulticastAddress(); eth.toByteArray(uuidBytes, 10); setTimestamp(ts, uuidBytes, getRandomClockSequence(), timeoffset); return uuid(uuidBytes); } /** * Generate a new UUID with the given time stamp in milliseconds. This method guarantees that subsequent calls will * be of increasing value chronologically. If a large number of subsequent calls are made to this method (>1000) * with the same timestamp, you will have non-unique temporal values stored in your UUID. */ public static UUID newTimeUUID(long ts) { tsLock.lock(); int pointer = customMicrosPointer.getAndIncrement(); try { if (pointer > 990) { customMicrosPointer.set(0); } } finally { tsLock.unlock(); } return newTimeUUID(ts, MICROS[pointer]); } public static UUID minTimeUUID(long ts) { byte[] uuidBytes = new byte[16]; setTimestamp(ts, uuidBytes, 0, 0); return uuid(uuidBytes); } public static UUID maxTimeUUID(long ts) { byte[] uuidBytes = new byte[16]; uuidBytes[10] = (byte) 0xFF; uuidBytes[11] = (byte) 0xFF; uuidBytes[12] = (byte) 0xFF; uuidBytes[13] = (byte) 0xFF; uuidBytes[14] = (byte) 0xFF; uuidBytes[15] = (byte) 0xFF; setTimestamp(ts, uuidBytes, 0x3FFF, 0x1FFF); return uuid(uuidBytes); } /** Returns the minimum UUID */ public static UUID min(UUID first, UUID second) { if (first == null) { if (second == null) { return null; } return second; } if (second == null) { return first; } if (compare(first, second) < 0) { return first; } return second; } /** Returns the minimum UUID */ public static UUID max(UUID first, UUID second) { if (first == null) { if (second == null) { return null; } return second; } if (second == null) { return first; } if (compare(first, second) < 0) { return second; } return first; } /** Returns a UUID that is -1 of the passed uuid, sorted by time uuid only */ public static UUID decrement(UUID uuid) { if (!isTimeBased(uuid)) { throw new IllegalArgumentException("The uuid must be a time type"); } //timestamp is in the 60 bit timestamp long timestamp = uuid.timestamp(); timestamp--; if (timestamp < 0) { throw new IllegalArgumentException("You must specify a time uuid with a timestamp > 0"); } //get our bytes, then set the smaller timestamp into it byte[] uuidBytes = bytes(uuid); setTime(uuidBytes, timestamp); return uuid(uuidBytes); } public static boolean isTimeBased(UUID uuid) { if (uuid == null) { return false; } return uuid.version() == 1; } public static long getTimestampInMillis(UUID uuid) { if (uuid == null) { return 0; } long t = uuid.timestamp(); return (t - KCLOCK_OFFSET) / KCLOCK_MULTIPLIER_L; } public static long getTimestampInMicros(UUID uuid) { if (uuid == null) { return 0; } long t = uuid.timestamp(); return (t - KCLOCK_OFFSET) / 10; } public static UUID tryGetUUID(String s) { if (s == null) { return null; } if (s.length() != 36) { return null; } // 8-4-4-4-12 // 0-7,8,9-12,13,14-17,18,19-22,23,24-35 if (s.charAt(8) != '-') { return null; } if (s.charAt(13) != '-') { return null; } if (s.charAt(18) != '-') { return null; } if (s.charAt(23) != '-') { return null; } UUID uuid = null; try { uuid = UUID.fromString(s); } catch (Exception e) { LOG.info("Could not convert String {} into a UUID", s, e); } return uuid; } public static boolean isUUID(String s) { return tryGetUUID(s) != null; } public static UUID tryExtractUUID(String s) { if (s == null) { return null; } if (s.length() < 36) { return null; } return tryGetUUID(s.substring(0, 36)); } public static UUID tryExtractUUID(String s, int offset) { if (s == null) { return null; } if ((s.length() - offset) < 36) { return null; } return tryGetUUID(s.substring(offset, offset + 36)); } public static String toBase64(UUID id) { if (id == null) { return null; } return encodeBase64URLSafeString(bytes(id)); } public static UUID fromBase64(String str) { if (str == null) { return null; } byte[] bytes = decodeBase64(str); if (bytes.length != 16) { return null; } return uuid(bytes); } public static int compare(UUID u1, UUID u2) { return UUIDComparator.staticCompare(u1, u2); } public static List<UUID> sort(List<UUID> uuids) { Collections.sort(uuids, UUID_COMPARATOR); return uuids; } }