| /**************************************************************** |
| * 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.IOException; |
| import java.io.OutputStream; |
| |
| /** |
| * This class implements an output stream that can be used to create a |
| * {@link Storage} object. An instance of this class is obtained by calling |
| * {@link StorageProvider#createStorageOutputStream()}. The user can then write |
| * data to this instance and invoke {@link #toStorage()} to retrieve a |
| * {@link Storage} object that contains the data that has been written. |
| * <p> |
| * Note that the <code>StorageOutputStream</code> does not have to be closed |
| * explicitly because {@link #toStorage()} invokes {@link #close()} if |
| * necessary. Also note that {@link #toStorage()} may be invoked only once. One |
| * <code>StorageOutputStream</code> can create only one <code>Storage</code> |
| * instance. |
| */ |
| public abstract class StorageOutputStream extends OutputStream { |
| |
| private byte[] singleByte; |
| private boolean closed; |
| private boolean usedUp; |
| |
| /** |
| * Sole constructor. |
| */ |
| protected StorageOutputStream() { |
| } |
| |
| /** |
| * Closes this output stream if it has not already been closed and returns a |
| * {@link Storage} object which contains the bytes that have been written to |
| * this output stream. |
| * <p> |
| * Note that this method may not be invoked a second time. This is because |
| * for some implementations it is not possible to create another |
| * <code>Storage</code> object that can be read from and deleted |
| * independently (e.g. if the implementation writes to a file). |
| * |
| * @return a <code>Storage</code> object as described above. |
| * @throws IOException |
| * if an I/O error occurs. |
| * @throws IllegalStateException |
| * if this method has already been called. |
| */ |
| public final Storage toStorage() throws IOException { |
| if (usedUp) |
| throw new IllegalStateException( |
| "toStorage may be invoked only once"); |
| |
| if (!closed) |
| close(); |
| |
| usedUp = true; |
| return toStorage0(); |
| } |
| |
| @Override |
| public final void write(int b) throws IOException { |
| if (closed) |
| throw new IOException("StorageOutputStream has been closed"); |
| |
| if (singleByte == null) |
| singleByte = new byte[1]; |
| |
| singleByte[0] = (byte) b; |
| write0(singleByte, 0, 1); |
| } |
| |
| @Override |
| public final void write(byte[] buffer) throws IOException { |
| if (closed) |
| throw new IOException("StorageOutputStream has been closed"); |
| |
| if (buffer == null) |
| throw new NullPointerException(); |
| |
| if (buffer.length == 0) |
| return; |
| |
| write0(buffer, 0, buffer.length); |
| } |
| |
| @Override |
| public final void write(byte[] buffer, int offset, int length) |
| throws IOException { |
| if (closed) |
| throw new IOException("StorageOutputStream has been closed"); |
| |
| if (buffer == null) |
| throw new NullPointerException(); |
| |
| if (offset < 0 || length < 0 || offset + length > buffer.length) |
| throw new IndexOutOfBoundsException(); |
| |
| if (length == 0) |
| return; |
| |
| write0(buffer, offset, length); |
| } |
| |
| /** |
| * Closes this output stream. Subclasses that override this method have to |
| * invoke <code>super.close()</code>. |
| * <p> |
| * This implementation never throws an {@link IOException} but a subclass |
| * might. |
| * |
| * @throws IOException |
| * if an I/O error occurs. |
| */ |
| @Override |
| public void close() throws IOException { |
| closed = true; |
| } |
| |
| /** |
| * Has to implemented by a concrete subclass to write bytes from the given |
| * byte array to this <code>StorageOutputStream</code>. This method gets |
| * called by {@link #write(int)}, {@link #write(byte[])} and |
| * {@link #write(byte[], int, int)}. All the required preconditions have |
| * already been checked by these methods, including the check if the output |
| * stream has already been closed. |
| * |
| * @param buffer |
| * buffer containing bytes to write. |
| * @param offset |
| * start offset in the buffer. |
| * @param length |
| * number of bytes to write. |
| * @throws IOException |
| * if an I/O error occurs. |
| */ |
| protected abstract void write0(byte[] buffer, int offset, int length) |
| throws IOException; |
| |
| /** |
| * Has to be implemented by a concrete subclass to create a {@link Storage} |
| * object from the bytes that have been written to this |
| * <code>StorageOutputStream</code>. This method gets called by |
| * {@link #toStorage()} after the preconditions have been checked. The |
| * implementation can also be sure that this methods gets invoked only once. |
| * |
| * @return a <code>Storage</code> object as described above. |
| * @throws IOException |
| * if an I/O error occurs. |
| */ |
| protected abstract Storage toStorage0() throws IOException; |
| |
| } |