| /**************************************************************** |
| * 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 org.apache.james.mime4j.storage; |
| |
| import java.io.ByteArrayInputStream; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.SequenceInputStream; |
| |
| import org.apache.james.mime4j.util.ByteArrayBuffer; |
| |
| /** |
| * A {@link StorageProvider} that keeps small amounts of data in memory and |
| * writes the remainder to another <code>StorageProvider</code> (the back-end) |
| * if a certain threshold size gets exceeded. |
| * <p> |
| * Example usage: |
| * |
| * <pre> |
| * StorageProvider tempStore = new TempFileStorageProvider(); |
| * StorageProvider provider = new ThresholdStorageProvider(tempStore, 4096); |
| * DefaultStorageProvider.setInstance(provider); |
| * </pre> |
| */ |
| public class ThresholdStorageProvider extends AbstractStorageProvider { |
| |
| private final StorageProvider backend; |
| private final int thresholdSize; |
| |
| /** |
| * Creates a new <code>ThresholdStorageProvider</code> for the given |
| * back-end using a threshold size of 2048 bytes. |
| */ |
| public ThresholdStorageProvider(StorageProvider backend) { |
| this(backend, 2048); |
| } |
| |
| /** |
| * Creates a new <code>ThresholdStorageProvider</code> for the given |
| * back-end and threshold size. |
| * |
| * @param backend |
| * used to store the remainder of the data if the threshold size |
| * gets exceeded. |
| * @param thresholdSize |
| * determines how much bytes are kept in memory before that |
| * back-end storage provider is used to store the remainder of |
| * the data. |
| */ |
| public ThresholdStorageProvider(StorageProvider backend, int thresholdSize) { |
| if (backend == null) |
| throw new IllegalArgumentException(); |
| if (thresholdSize < 1) |
| throw new IllegalArgumentException(); |
| |
| this.backend = backend; |
| this.thresholdSize = thresholdSize; |
| } |
| |
| public StorageOutputStream createStorageOutputStream() { |
| return new ThresholdStorageOutputStream(); |
| } |
| |
| private final class ThresholdStorageOutputStream extends |
| StorageOutputStream { |
| |
| private final ByteArrayBuffer head; |
| private StorageOutputStream tail; |
| |
| public ThresholdStorageOutputStream() { |
| final int bufferSize = Math.min(thresholdSize, 1024); |
| head = new ByteArrayBuffer(bufferSize); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| super.close(); |
| |
| if (tail != null) |
| tail.close(); |
| } |
| |
| @Override |
| protected void write0(byte[] buffer, int offset, int length) |
| throws IOException { |
| int remainingHeadSize = thresholdSize - head.length(); |
| if (remainingHeadSize > 0) { |
| int n = Math.min(remainingHeadSize, length); |
| head.append(buffer, offset, n); |
| offset += n; |
| length -= n; |
| } |
| |
| if (length > 0) { |
| if (tail == null) |
| tail = backend.createStorageOutputStream(); |
| |
| tail.write(buffer, offset, length); |
| } |
| } |
| |
| @Override |
| protected Storage toStorage0() throws IOException { |
| if (tail == null) |
| return new MemoryStorageProvider.MemoryStorage(head.buffer(), |
| head.length()); |
| |
| return new ThresholdStorage(head.buffer(), head.length(), tail |
| .toStorage()); |
| } |
| |
| } |
| |
| private static final class ThresholdStorage implements Storage { |
| |
| private byte[] head; |
| private final int headLen; |
| private Storage tail; |
| |
| public ThresholdStorage(byte[] head, int headLen, Storage tail) { |
| this.head = head; |
| this.headLen = headLen; |
| this.tail = tail; |
| } |
| |
| public void delete() { |
| if (head != null) { |
| head = null; |
| tail.delete(); |
| tail = null; |
| } |
| } |
| |
| public InputStream getInputStream() throws IOException { |
| if (head == null) |
| throw new IllegalStateException("storage has been deleted"); |
| |
| InputStream headStream = new ByteArrayInputStream(head, 0, headLen); |
| InputStream tailStream = tail.getInputStream(); |
| return new SequenceInputStream(headStream, tailStream); |
| } |
| |
| } |
| } |