[6785] | 1 | /**************************************************************** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one * |
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| 3 | * or more contributor license agreements. See the NOTICE file * |
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| 4 | * distributed with this work for additional information * |
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| 5 | * regarding copyright ownership. The ASF licenses this file * |
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| 6 | * to you under the Apache License, Version 2.0 (the * |
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| 7 | * "License"); you may not use this file except in compliance * |
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| 8 | * with the License. You may obtain a copy of the License at * |
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| 9 | * * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 * |
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| 11 | * * |
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| 12 | * Unless required by applicable law or agreed to in writing, * |
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| 13 | * software distributed under the License is distributed on an * |
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| 14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * |
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| 15 | * KIND, either express or implied. See the License for the * |
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| 16 | * specific language governing permissions and limitations * |
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| 17 | * under the License. * |
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| 18 | ****************************************************************/ |
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| 19 | |
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| 20 | package org.apache.james.mime4j.storage; |
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| 21 | |
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| 22 | import java.io.ByteArrayInputStream; |
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| 23 | import java.io.IOException; |
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| 24 | import java.io.InputStream; |
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| 25 | import java.io.SequenceInputStream; |
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| 26 | |
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| 27 | import org.apache.james.mime4j.util.ByteArrayBuffer; |
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| 28 | |
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| 29 | /** |
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| 30 | * A {@link StorageProvider} that keeps small amounts of data in memory and |
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| 31 | * writes the remainder to another <code>StorageProvider</code> (the back-end) |
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| 32 | * if a certain threshold size gets exceeded. |
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| 33 | * <p> |
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| 34 | * Example usage: |
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| 35 | * |
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| 36 | * <pre> |
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| 37 | * StorageProvider tempStore = new TempFileStorageProvider(); |
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| 38 | * StorageProvider provider = new ThresholdStorageProvider(tempStore, 4096); |
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| 39 | * DefaultStorageProvider.setInstance(provider); |
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| 40 | * </pre> |
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| 41 | */ |
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| 42 | public class ThresholdStorageProvider extends AbstractStorageProvider { |
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| 43 | |
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| 44 | private final StorageProvider backend; |
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| 45 | private final int thresholdSize; |
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| 46 | |
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| 47 | /** |
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| 48 | * Creates a new <code>ThresholdStorageProvider</code> for the given |
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| 49 | * back-end using a threshold size of 2048 bytes. |
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| 50 | */ |
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| 51 | public ThresholdStorageProvider(StorageProvider backend) { |
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| 52 | this(backend, 2048); |
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| 53 | } |
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| 54 | |
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| 55 | /** |
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| 56 | * Creates a new <code>ThresholdStorageProvider</code> for the given |
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| 57 | * back-end and threshold size. |
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| 58 | * |
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| 59 | * @param backend |
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| 60 | * used to store the remainder of the data if the threshold size |
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| 61 | * gets exceeded. |
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| 62 | * @param thresholdSize |
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| 63 | * determines how much bytes are kept in memory before that |
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| 64 | * back-end storage provider is used to store the remainder of |
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| 65 | * the data. |
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| 66 | */ |
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| 67 | public ThresholdStorageProvider(StorageProvider backend, int thresholdSize) { |
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| 68 | if (backend == null) |
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| 69 | throw new IllegalArgumentException(); |
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| 70 | if (thresholdSize < 1) |
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| 71 | throw new IllegalArgumentException(); |
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| 72 | |
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| 73 | this.backend = backend; |
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| 74 | this.thresholdSize = thresholdSize; |
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| 75 | } |
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| 76 | |
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| 77 | public StorageOutputStream createStorageOutputStream() { |
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| 78 | return new ThresholdStorageOutputStream(); |
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| 79 | } |
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| 80 | |
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| 81 | private final class ThresholdStorageOutputStream extends |
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| 82 | StorageOutputStream { |
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| 83 | |
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| 84 | private final ByteArrayBuffer head; |
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| 85 | private StorageOutputStream tail; |
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| 86 | |
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| 87 | public ThresholdStorageOutputStream() { |
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| 88 | final int bufferSize = Math.min(thresholdSize, 1024); |
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| 89 | head = new ByteArrayBuffer(bufferSize); |
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| 90 | } |
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| 91 | |
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| 92 | @Override |
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| 93 | public void close() throws IOException { |
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| 94 | super.close(); |
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| 95 | |
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| 96 | if (tail != null) |
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| 97 | tail.close(); |
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| 98 | } |
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| 99 | |
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| 100 | @Override |
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| 101 | protected void write0(byte[] buffer, int offset, int length) |
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| 102 | throws IOException { |
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| 103 | int remainingHeadSize = thresholdSize - head.length(); |
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| 104 | if (remainingHeadSize > 0) { |
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| 105 | int n = Math.min(remainingHeadSize, length); |
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| 106 | head.append(buffer, offset, n); |
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| 107 | offset += n; |
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| 108 | length -= n; |
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| 109 | } |
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| 110 | |
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| 111 | if (length > 0) { |
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| 112 | if (tail == null) |
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| 113 | tail = backend.createStorageOutputStream(); |
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| 114 | |
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| 115 | tail.write(buffer, offset, length); |
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| 116 | } |
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| 117 | } |
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| 118 | |
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| 119 | @Override |
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| 120 | protected Storage toStorage0() throws IOException { |
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| 121 | if (tail == null) |
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| 122 | return new MemoryStorageProvider.MemoryStorage(head.buffer(), |
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| 123 | head.length()); |
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| 124 | |
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| 125 | return new ThresholdStorage(head.buffer(), head.length(), tail |
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| 126 | .toStorage()); |
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| 127 | } |
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| 128 | |
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| 129 | } |
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| 130 | |
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| 131 | private static final class ThresholdStorage implements Storage { |
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| 132 | |
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| 133 | private byte[] head; |
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| 134 | private final int headLen; |
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| 135 | private Storage tail; |
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| 136 | |
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| 137 | public ThresholdStorage(byte[] head, int headLen, Storage tail) { |
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| 138 | this.head = head; |
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| 139 | this.headLen = headLen; |
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| 140 | this.tail = tail; |
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| 141 | } |
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| 142 | |
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| 143 | public void delete() { |
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| 144 | if (head != null) { |
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| 145 | head = null; |
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| 146 | tail.delete(); |
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| 147 | tail = null; |
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| 148 | } |
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| 149 | } |
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| 150 | |
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| 151 | public InputStream getInputStream() throws IOException { |
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| 152 | if (head == null) |
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| 153 | throw new IllegalStateException("storage has been deleted"); |
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| 154 | |
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| 155 | InputStream headStream = new ByteArrayInputStream(head, 0, headLen); |
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| 156 | InputStream tailStream = tail.getInputStream(); |
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| 157 | return new SequenceInputStream(headStream, tailStream); |
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| 158 | } |
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| 159 | |
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| 160 | } |
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| 161 | } |
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