1 | /**************************************************************** |
---|
2 | * Licensed to the Apache Software Foundation (ASF) under one * |
---|
3 | * or more contributor license agreements. See the NOTICE file * |
---|
4 | * distributed with this work for additional information * |
---|
5 | * regarding copyright ownership. The ASF licenses this file * |
---|
6 | * to you under the Apache License, Version 2.0 (the * |
---|
7 | * "License"); you may not use this file except in compliance * |
---|
8 | * with the License. You may obtain a copy of the License at * |
---|
9 | * * |
---|
10 | * http://www.apache.org/licenses/LICENSE-2.0 * |
---|
11 | * * |
---|
12 | * Unless required by applicable law or agreed to in writing, * |
---|
13 | * software distributed under the License is distributed on an * |
---|
14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * |
---|
15 | * KIND, either express or implied. See the License for the * |
---|
16 | * specific language governing permissions and limitations * |
---|
17 | * under the License. * |
---|
18 | ****************************************************************/ |
---|
19 | |
---|
20 | package org.apache.james.mime4j.storage; |
---|
21 | |
---|
22 | import java.io.IOException; |
---|
23 | import java.io.OutputStream; |
---|
24 | |
---|
25 | /** |
---|
26 | * This class implements an output stream that can be used to create a |
---|
27 | * {@link Storage} object. An instance of this class is obtained by calling |
---|
28 | * {@link StorageProvider#createStorageOutputStream()}. The user can then write |
---|
29 | * data to this instance and invoke {@link #toStorage()} to retrieve a |
---|
30 | * {@link Storage} object that contains the data that has been written. |
---|
31 | * <p> |
---|
32 | * Note that the <code>StorageOutputStream</code> does not have to be closed |
---|
33 | * explicitly because {@link #toStorage()} invokes {@link #close()} if |
---|
34 | * necessary. Also note that {@link #toStorage()} may be invoked only once. One |
---|
35 | * <code>StorageOutputStream</code> can create only one <code>Storage</code> |
---|
36 | * instance. |
---|
37 | */ |
---|
38 | public abstract class StorageOutputStream extends OutputStream { |
---|
39 | |
---|
40 | private byte[] singleByte; |
---|
41 | private boolean closed; |
---|
42 | private boolean usedUp; |
---|
43 | |
---|
44 | /** |
---|
45 | * Sole constructor. |
---|
46 | */ |
---|
47 | protected StorageOutputStream() { |
---|
48 | } |
---|
49 | |
---|
50 | /** |
---|
51 | * Closes this output stream if it has not already been closed and returns a |
---|
52 | * {@link Storage} object which contains the bytes that have been written to |
---|
53 | * this output stream. |
---|
54 | * <p> |
---|
55 | * Note that this method may not be invoked a second time. This is because |
---|
56 | * for some implementations it is not possible to create another |
---|
57 | * <code>Storage</code> object that can be read from and deleted |
---|
58 | * independently (e.g. if the implementation writes to a file). |
---|
59 | * |
---|
60 | * @return a <code>Storage</code> object as described above. |
---|
61 | * @throws IOException |
---|
62 | * if an I/O error occurs. |
---|
63 | * @throws IllegalStateException |
---|
64 | * if this method has already been called. |
---|
65 | */ |
---|
66 | public final Storage toStorage() throws IOException { |
---|
67 | if (usedUp) |
---|
68 | throw new IllegalStateException( |
---|
69 | "toStorage may be invoked only once"); |
---|
70 | |
---|
71 | if (!closed) |
---|
72 | close(); |
---|
73 | |
---|
74 | usedUp = true; |
---|
75 | return toStorage0(); |
---|
76 | } |
---|
77 | |
---|
78 | @Override |
---|
79 | public final void write(int b) throws IOException { |
---|
80 | if (closed) |
---|
81 | throw new IOException("StorageOutputStream has been closed"); |
---|
82 | |
---|
83 | if (singleByte == null) |
---|
84 | singleByte = new byte[1]; |
---|
85 | |
---|
86 | singleByte[0] = (byte) b; |
---|
87 | write0(singleByte, 0, 1); |
---|
88 | } |
---|
89 | |
---|
90 | @Override |
---|
91 | public final void write(byte[] buffer) throws IOException { |
---|
92 | if (closed) |
---|
93 | throw new IOException("StorageOutputStream has been closed"); |
---|
94 | |
---|
95 | if (buffer == null) |
---|
96 | throw new NullPointerException(); |
---|
97 | |
---|
98 | if (buffer.length == 0) |
---|
99 | return; |
---|
100 | |
---|
101 | write0(buffer, 0, buffer.length); |
---|
102 | } |
---|
103 | |
---|
104 | @Override |
---|
105 | public final void write(byte[] buffer, int offset, int length) |
---|
106 | throws IOException { |
---|
107 | if (closed) |
---|
108 | throw new IOException("StorageOutputStream has been closed"); |
---|
109 | |
---|
110 | if (buffer == null) |
---|
111 | throw new NullPointerException(); |
---|
112 | |
---|
113 | if (offset < 0 || length < 0 || offset + length > buffer.length) |
---|
114 | throw new IndexOutOfBoundsException(); |
---|
115 | |
---|
116 | if (length == 0) |
---|
117 | return; |
---|
118 | |
---|
119 | write0(buffer, offset, length); |
---|
120 | } |
---|
121 | |
---|
122 | /** |
---|
123 | * Closes this output stream. Subclasses that override this method have to |
---|
124 | * invoke <code>super.close()</code>. |
---|
125 | * <p> |
---|
126 | * This implementation never throws an {@link IOException} but a subclass |
---|
127 | * might. |
---|
128 | * |
---|
129 | * @throws IOException |
---|
130 | * if an I/O error occurs. |
---|
131 | */ |
---|
132 | @Override |
---|
133 | public void close() throws IOException { |
---|
134 | closed = true; |
---|
135 | } |
---|
136 | |
---|
137 | /** |
---|
138 | * Has to implemented by a concrete subclass to write bytes from the given |
---|
139 | * byte array to this <code>StorageOutputStream</code>. This method gets |
---|
140 | * called by {@link #write(int)}, {@link #write(byte[])} and |
---|
141 | * {@link #write(byte[], int, int)}. All the required preconditions have |
---|
142 | * already been checked by these methods, including the check if the output |
---|
143 | * stream has already been closed. |
---|
144 | * |
---|
145 | * @param buffer |
---|
146 | * buffer containing bytes to write. |
---|
147 | * @param offset |
---|
148 | * start offset in the buffer. |
---|
149 | * @param length |
---|
150 | * number of bytes to write. |
---|
151 | * @throws IOException |
---|
152 | * if an I/O error occurs. |
---|
153 | */ |
---|
154 | protected abstract void write0(byte[] buffer, int offset, int length) |
---|
155 | throws IOException; |
---|
156 | |
---|
157 | /** |
---|
158 | * Has to be implemented by a concrete subclass to create a {@link Storage} |
---|
159 | * object from the bytes that have been written to this |
---|
160 | * <code>StorageOutputStream</code>. This method gets called by |
---|
161 | * {@link #toStorage()} after the preconditions have been checked. The |
---|
162 | * implementation can also be sure that this methods gets invoked only once. |
---|
163 | * |
---|
164 | * @return a <code>Storage</code> object as described above. |
---|
165 | * @throws IOException |
---|
166 | * if an I/O error occurs. |
---|
167 | */ |
---|
168 | protected abstract Storage toStorage0() throws IOException; |
---|
169 | |
---|
170 | } |
---|