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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