001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.activemq.transport.amqp.protocol; 018 019import java.io.UnsupportedEncodingException; 020import java.util.Iterator; 021import java.util.LinkedHashSet; 022import java.util.Set; 023 024/** 025 * Utility class that can generate and if enabled pool the binary tag values 026 * used to identify transfers over an AMQP link. 027 */ 028public final class AmqpTransferTagGenerator { 029 030 public static final int DEFAULT_TAG_POOL_SIZE = 1024; 031 032 private long nextTagId; 033 private int maxPoolSize = DEFAULT_TAG_POOL_SIZE; 034 035 private final Set<byte[]> tagPool; 036 037 public AmqpTransferTagGenerator() { 038 this(false); 039 } 040 041 public AmqpTransferTagGenerator(boolean pool) { 042 if (pool) { 043 this.tagPool = new LinkedHashSet<byte[]>(); 044 } else { 045 this.tagPool = null; 046 } 047 } 048 049 /** 050 * Retrieves the next available tag. 051 * 052 * @return a new or unused tag depending on the pool option. 053 */ 054 public byte[] getNextTag() { 055 byte[] rc; 056 if (tagPool != null && !tagPool.isEmpty()) { 057 final Iterator<byte[]> iterator = tagPool.iterator(); 058 rc = iterator.next(); 059 iterator.remove(); 060 } else { 061 try { 062 rc = Long.toHexString(nextTagId++).getBytes("UTF-8"); 063 } catch (UnsupportedEncodingException e) { 064 // This should never happen since we control the input. 065 throw new RuntimeException(e); 066 } 067 } 068 return rc; 069 } 070 071 /** 072 * When used as a pooled cache of tags the unused tags should always be returned once 073 * the transfer has been settled. 074 * 075 * @param data 076 * a previously borrowed tag that is no longer in use. 077 */ 078 public void returnTag(byte[] data) { 079 if (tagPool != null && tagPool.size() < maxPoolSize) { 080 tagPool.add(data); 081 } 082 } 083 084 /** 085 * Gets the current max pool size value. 086 * 087 * @return the current max tag pool size. 088 */ 089 public int getMaxPoolSize() { 090 return maxPoolSize; 091 } 092 093 /** 094 * Sets the max tag pool size. If the size is smaller than the current number 095 * of pooled tags the pool will drain over time until it matches the max. 096 * 097 * @param maxPoolSize 098 * the maximum number of tags to hold in the pool. 099 */ 100 public void setMaxPoolSize(int maxPoolSize) { 101 this.maxPoolSize = maxPoolSize; 102 } 103}