Java tutorial
package org.apache.cassandra.db.marshal; /* * * 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. * */ import java.nio.ByteBuffer; import java.text.ParseException; import java.util.UUID; import org.apache.cassandra.utils.ByteBufferUtil; import org.apache.cassandra.utils.FBUtilities; import org.apache.cassandra.utils.UUIDGen; import org.apache.commons.lang.time.DateUtils; /** * Compares UUIDs using the following criteria:<br> * - if count of supplied bytes is less than 16, compare counts<br> * - compare UUID version fields<br> * - nil UUID is always lesser<br> * - compare timestamps if both are time-based<br> * - compare lexically, unsigned msb-to-lsb comparison<br> * * @see "com.fasterxml.uuid.UUIDComparator" */ public class UUIDType extends AbstractUUIDType { public static final UUIDType instance = new UUIDType(); UUIDType() { } public int compare(ByteBuffer b1, ByteBuffer b2) { // Compare for length if ((b1 == null) || (b1.remaining() < 16)) { return ((b2 == null) || (b2.remaining() < 16)) ? 0 : -1; } if ((b2 == null) || (b2.remaining() < 16)) { return 1; } int s1 = b1.position(); int s2 = b2.position(); // Compare versions int v1 = (b1.get(s1 + 6) >> 4) & 0x0f; int v2 = (b2.get(s2 + 6) >> 4) & 0x0f; if (v1 != v2) { return v1 - v2; } // Compare timestamps for version 1 if (v1 == 1) { // if both time-based, compare as timestamps int c = compareTimestampBytes(b1, b2); if (c != 0) { return c; } } // Compare the two byte arrays starting from the first // byte in the sequence until an inequality is // found. This should provide equivalent results // to the comparison performed by the RFC 4122 // Appendix A - Sample Implementation. // Note: java.util.UUID.compareTo is not a lexical // comparison for (int i = 0; i < 16; i++) { int c = ((b1.get(s1 + i)) & 0xFF) - ((b2.get(s2 + i)) & 0xFF); if (c != 0) { return c; } } return 0; } private static int compareTimestampBytes(ByteBuffer o1, ByteBuffer o2) { int o1Pos = o1.position(); int o2Pos = o2.position(); int d = (o1.get(o1Pos + 6) & 0xF) - (o2.get(o2Pos + 6) & 0xF); if (d != 0) { return d; } d = (o1.get(o1Pos + 7) & 0xFF) - (o2.get(o2Pos + 7) & 0xFF); if (d != 0) { return d; } d = (o1.get(o1Pos + 4) & 0xFF) - (o2.get(o2Pos + 4) & 0xFF); if (d != 0) { return d; } d = (o1.get(o1Pos + 5) & 0xFF) - (o2.get(o2Pos + 5) & 0xFF); if (d != 0) { return d; } d = (o1.get(o1Pos) & 0xFF) - (o2.get(o2Pos) & 0xFF); if (d != 0) { return d; } d = (o1.get(o1Pos + 1) & 0xFF) - (o2.get(o2Pos + 1) & 0xFF); if (d != 0) { return d; } d = (o1.get(o1Pos + 2) & 0xFF) - (o2.get(o2Pos + 2) & 0xFF); if (d != 0) { return d; } return (o1.get(o1Pos + 3) & 0xFF) - (o2.get(o2Pos + 3) & 0xFF); } public UUID compose(ByteBuffer bytes) { bytes = bytes.slice(); if (bytes.remaining() < 16) return new UUID(0, 0); return new UUID(bytes.getLong(), bytes.getLong()); } public String toString(UUID uuid) { return uuid.toString(); } public Class<UUID> getType() { return UUID.class; } public void validate(ByteBuffer bytes) { if ((bytes.remaining() != 0) && (bytes.remaining() != 16)) { throw new MarshalException("UUIDs must be exactly 16 bytes"); } } public String getString(ByteBuffer bytes) { if (bytes.remaining() == 0) { return ""; } if (bytes.remaining() != 16) { throw new MarshalException("UUIDs must be exactly 16 bytes"); } UUID uuid = compose(bytes); return uuid.toString(); } public ByteBuffer decompose(UUID value) { return ByteBuffer.wrap(UUIDGen.decompose(value)); } @Override public ByteBuffer fromString(String source) throws MarshalException { // Return an empty ByteBuffer for an empty string. if (source.isEmpty()) return ByteBufferUtil.EMPTY_BYTE_BUFFER; ByteBuffer idBytes = null; // ffffffff-ffff-ffff-ffff-ffffffffff if (TimeUUIDType.regexPattern.matcher(source).matches()) { UUID uuid; try { uuid = UUID.fromString(source); idBytes = ByteBuffer.wrap(UUIDGen.decompose(uuid)); } catch (IllegalArgumentException e) { throw new MarshalException(String.format("unable to make UUID from '%s'", source), e); } } else if (source.toLowerCase().equals("now")) { idBytes = ByteBuffer .wrap(UUIDGen.decompose(UUIDGen.makeType1UUIDFromHost(FBUtilities.getLocalAddress()))); } // Milliseconds since epoch? else if (source.matches("^\\d+$")) { try { idBytes = ByteBuffer.wrap(UUIDGen.getTimeUUIDBytes(Long.parseLong(source))); } catch (NumberFormatException e) { throw new MarshalException(String.format("unable to make version 1 UUID from '%s'", source), e); } } // Last chance, attempt to parse as date-time string else { try { long timestamp = DateUtils.parseDate(source, TimeUUIDType.iso8601Patterns).getTime(); idBytes = ByteBuffer.wrap(UUIDGen.getTimeUUIDBytes(timestamp)); } catch (ParseException e1) { throw new MarshalException(String.format("unable to coerce '%s' to version 1 UUID", source), e1); } } return idBytes; } }