1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 import java.util.Arrays;
29
30 /**
31 * This class implements an output stream in which the data is
32 * written into a byte array. The buffer automatically grows as data
33 * is written to it.
34 * The data can be retrieved using {@code toByteArray()} and
35 * {@code toString()}.
36 * <p>
37 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
38 * this class can be called after the stream has been closed without
39 * generating an {@code IOException}.
40 *
41 * @author Arthur van Hoff
42 * @since 1.0
43 */
44
45 public class ByteArrayOutputStream extends OutputStream {
46
47 /**
48 * The buffer where data is stored.
49 */
50 protected byte buf[];
51
52 /**
53 * The number of valid bytes in the buffer.
54 */
55 protected int count;
56
57 /**
58 * Creates a new byte array output stream. The buffer capacity is
59 * initially 32 bytes, though its size increases if necessary.
60 */
61 public ByteArrayOutputStream() {
62 this(32);
63 }
64
65 /**
66 * Creates a new byte array output stream, with a buffer capacity of
67 * the specified size, in bytes.
68 *
69 * @param size the initial size.
70 * @exception IllegalArgumentException if size is negative.
71 */
72 public ByteArrayOutputStream(int size) {
73 if (size < 0) {
74 throw new IllegalArgumentException("Negative initial size: "
75 + size);
76 }
77 buf = new byte[size];
78 }
79
80 /**
81 * Increases the capacity if necessary to ensure that it can hold
82 * at least the number of elements specified by the minimum
83 * capacity argument.
84 *
85 * @param minCapacity the desired minimum capacity
86 * @throws OutOfMemoryError if {@code minCapacity < 0}. This is
87 * interpreted as a request for the unsatisfiably large capacity
88 * {@code (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE)}.
89 */
90 private void ensureCapacity(int minCapacity) {
91 // overflow-conscious code
92 if (minCapacity - buf.length > 0)
93 grow(minCapacity);
94 }
95
96 /**
97 * The maximum size of array to allocate.
98 * Some VMs reserve some header words in an array.
99 * Attempts to allocate larger arrays may result in
100 * OutOfMemoryError: Requested array size exceeds VM limit
101 */
102 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
103
104 /**
105 * Increases the capacity to ensure that it can hold at least the
106 * number of elements specified by the minimum capacity argument.
107 *
108 * @param minCapacity the desired minimum capacity
109 */
110 private void grow(int minCapacity) {
111 // overflow-conscious code
112 int oldCapacity = buf.length;
113 int newCapacity = oldCapacity << 1;
114 if (newCapacity - minCapacity < 0)
115 newCapacity = minCapacity;
116 if (newCapacity - MAX_ARRAY_SIZE > 0)
117 newCapacity = hugeCapacity(minCapacity);
118 buf = Arrays.copyOf(buf, newCapacity);
119 }
120
121 private static int hugeCapacity(int minCapacity) {
122 if (minCapacity < 0) // overflow
123 throw new OutOfMemoryError();
124 return (minCapacity > MAX_ARRAY_SIZE) ?
125 Integer.MAX_VALUE :
126 MAX_ARRAY_SIZE;
127 }
128
129 /**
130 * Writes the specified byte to this byte array output stream.
131 *
132 * @param b the byte to be written.
133 */
134 public synchronized void write(int b) {
135 ensureCapacity(count + 1);
136 buf[count] = (byte) b;
137 count += 1;
138 }
139
140 /**
141 * Writes {@code len} bytes from the specified byte array
142 * starting at offset {@code off} to this byte array output stream.
143 *
144 * @param b the data.
145 * @param off the start offset in the data.
146 * @param len the number of bytes to write.
147 */
148 public synchronized void write(byte b[], int off, int len) {
149 if ((off < 0) || (off > b.length) || (len < 0) ||
150 ((off + len) - b.length > 0)) {
151 throw new IndexOutOfBoundsException();
152 }
153 ensureCapacity(count + len);
154 System.arraycopy(b, off, buf, count, len);
155 count += len;
156 }
157
158 /**
159 * Writes the complete contents of this byte array output stream to
160 * the specified output stream argument, as if by calling the output
161 * stream's write method using {@code out.write(buf, 0, count)}.
162 *
163 * @param out the output stream to which to write the data.
164 * @exception IOException if an I/O error occurs.
165 */
166 public synchronized void writeTo(OutputStream out) throws IOException {
167 out.write(buf, 0, count);
168 }
169
170 /**
171 * Resets the {@code count} field of this byte array output
172 * stream to zero, so that all currently accumulated output in the
173 * output stream is discarded. The output stream can be used again,
174 * reusing the already allocated buffer space.
175 *
176 * @see java.io.ByteArrayInputStream#count
177 */
178 public synchronized void reset() {
179 count = 0;
180 }
181
182 /**
183 * Creates a newly allocated byte array. Its size is the current
184 * size of this output stream and the valid contents of the buffer
185 * have been copied into it.
186 *
187 * @return the current contents of this output stream, as a byte array.
188 * @see java.io.ByteArrayOutputStream#size()
189 */
190 public synchronized byte toByteArray()[] {
191 return Arrays.copyOf(buf, count);
192 }
193
194 /**
195 * Returns the current size of the buffer.
196 *
197 * @return the value of the {@code count} field, which is the number
198 * of valid bytes in this output stream.
199 * @see java.io.ByteArrayOutputStream#count
200 */
201 public synchronized int size() {
202 return count;
203 }
204
205 /**
206 * Converts the buffer's contents into a string decoding bytes using the
207 * platform's default character set. The length of the new {@code String}
208 * is a function of the character set, and hence may not be equal to the
209 * size of the buffer.
210 *
211 * <p> This method always replaces malformed-input and unmappable-character
212 * sequences with the default replacement string for the platform's
213 * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
214 * class should be used when more control over the decoding process is
215 * required.
216 *
217 * @return String decoded from the buffer's contents.
218 * @since 1.1
219 */
220 public synchronized String toString() {
221 return new String(buf, 0, count);
222 }
223
224 /**
225 * Converts the buffer's contents into a string by decoding the bytes using
226 * the named {@link java.nio.charset.Charset charset}. The length of the new
227 * {@code String} is a function of the charset, and hence may not be equal
228 * to the length of the byte array.
229 *
230 * <p> This method always replaces malformed-input and unmappable-character
231 * sequences with this charset's default replacement string. The {@link
232 * java.nio.charset.CharsetDecoder} class should be used when more control
233 * over the decoding process is required.
234 *
235 * @param charsetName the name of a supported
236 * {@link java.nio.charset.Charset charset}
237 * @return String decoded from the buffer's contents.
238 * @exception UnsupportedEncodingException
239 * If the named charset is not supported
240 * @since 1.1
241 */
242 public synchronized String toString(String charsetName)
243 throws UnsupportedEncodingException
244 {
245 return new String(buf, 0, count, charsetName);
246 }
247
248 /**
249 * Creates a newly allocated string. Its size is the current size of
250 * the output stream and the valid contents of the buffer have been
251 * copied into it. Each character <i>c</i> in the resulting string is
252 * constructed from the corresponding element <i>b</i> in the byte
253 * array such that:
254 * <blockquote><pre>{@code
255 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
256 * }</pre></blockquote>
257 *
258 * @deprecated This method does not properly convert bytes into characters.
259 * As of JDK 1.1, the preferred way to do this is via the
260 * {@code toString(String enc)} method, which takes an encoding-name
261 * argument, or the {@code toString()} method, which uses the
262 * platform's default character encoding.
263 *
264 * @param hibyte the high byte of each resulting Unicode character.
265 * @return the current contents of the output stream, as a string.
266 * @see java.io.ByteArrayOutputStream#size()
267 * @see java.io.ByteArrayOutputStream#toString(String)
268 * @see java.io.ByteArrayOutputStream#toString()
269 */
270 @Deprecated
271 public synchronized String toString(int hibyte) {
272 return new String(buf, hibyte, 0, count);
273 }
274
275 /**
276 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
277 * this class can be called after the stream has been closed without
278 * generating an {@code IOException}.
279 */
280 public void close() throws IOException {
281 }
282
283 }