1 /*
2 * Copyright (c) 1994, 2024, 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.nio.charset.Charset;
29 import java.util.Arrays;
30 import java.util.Objects;
31
32 import jdk.internal.util.ArraysSupport;
33
34 /**
35 * This class implements an output stream in which the data is
36 * written into a byte array. The buffer automatically grows as data
37 * is written to it.
38 * The data can be retrieved using {@code toByteArray()} and
39 * {@code toString()}.
40 * <p>
41 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
42 * this class can be called after the stream has been closed without
43 * generating an {@code IOException}.
44 *
45 * @author Arthur van Hoff
46 * @since 1.0
47 */
48
49 public class ByteArrayOutputStream extends OutputStream {
50
51 /**
52 * The buffer where data is stored.
53 */
54 protected byte[] buf;
55
56 /**
57 * The number of valid bytes in the buffer.
58 */
59 protected int count;
60
61 /**
62 * Creates a new {@code ByteArrayOutputStream}. The buffer capacity is
63 * initially 32 bytes, though its size increases if necessary.
64 */
65 public ByteArrayOutputStream() {
66 this(32);
67 }
68
69 /**
70 * Creates a new {@code ByteArrayOutputStream}, with a buffer capacity of
71 * the specified size, in bytes.
72 *
73 * @param size the initial size.
74 * @throws IllegalArgumentException if size is negative.
75 */
76 public ByteArrayOutputStream(int size) {
77 if (size < 0) {
78 throw new IllegalArgumentException("Negative initial size: "
79 + size);
80 }
81 buf = new byte[size];
82 }
83
84 /**
85 * Increases the capacity if necessary to ensure that it can hold
86 * at least the number of elements specified by the minimum
87 * capacity argument.
88 *
89 * @param minCapacity the desired minimum capacity.
90 * @throws OutOfMemoryError if {@code minCapacity < 0} and
91 * {@code minCapacity - buf.length > 0}. This is interpreted as a
92 * request for the unsatisfiably large capacity.
93 * {@code (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE)}.
94 */
95 private void ensureCapacity(int minCapacity) {
96 // overflow-conscious code
97 int oldCapacity = buf.length;
98 int minGrowth = minCapacity - oldCapacity;
99 if (minGrowth > 0) {
100 buf = Arrays.copyOf(buf, ArraysSupport.newLength(oldCapacity,
101 minGrowth, oldCapacity /* preferred growth */));
102 }
103 }
104
105 /**
106 * Writes the specified byte to this {@code ByteArrayOutputStream}.
107 *
108 * @param b the byte to be written.
109 */
110 @Override
111 public synchronized void write(int b) {
112 ensureCapacity(count + 1);
113 buf[count] = (byte) b;
114 count += 1;
115 }
116
117 /**
118 * Writes {@code len} bytes from the specified byte array
119 * starting at offset {@code off} to this {@code ByteArrayOutputStream}.
120 *
121 * @param b {@inheritDoc}
122 * @param off {@inheritDoc}
123 * @param len {@inheritDoc}
124 * @throws NullPointerException if {@code b} is {@code null}.
125 * @throws IndexOutOfBoundsException if {@code off} is negative,
126 * {@code len} is negative, or {@code len} is greater than
127 * {@code b.length - off}
128 */
129 @Override
130 public synchronized void write(byte[] b, int off, int len) {
131 Objects.checkFromIndexSize(off, len, b.length);
132 ensureCapacity(count + len);
133 System.arraycopy(b, off, buf, count, len);
134 count += len;
135 }
136
137 /**
138 * Writes the complete contents of the specified byte array
139 * to this {@code ByteArrayOutputStream}.
140 *
141 * @apiNote
142 * This method is equivalent to {@link #write(byte[],int,int)
143 * write(b, 0, b.length)}.
144 *
145 * @param b the data.
146 * @throws NullPointerException if {@code b} is {@code null}.
147 * @since 11
148 */
149 public void writeBytes(byte[] b) {
150 write(b, 0, b.length);
151 }
152
153 /**
154 * Writes the complete contents of this {@code ByteArrayOutputStream} to
155 * the specified output stream argument, as if by calling the output
156 * stream's write method using {@code out.write(buf, 0, count)}.
157 *
158 * @param out the output stream to which to write the data.
159 * @throws NullPointerException if {@code out} is {@code null}.
160 * @throws IOException if an I/O error occurs.
161 */
162 public void writeTo(OutputStream out) throws IOException {
163 if (Thread.currentThread().isVirtual()) {
164 byte[] bytes;
165 synchronized (this) {
166 bytes = Arrays.copyOf(buf, count);
167 }
168 out.write(bytes);
169 } else synchronized (this) {
170 out.write(buf, 0, count);
171 }
172 }
173
174 /**
175 * Resets the {@code count} field of this {@code ByteArrayOutputStream}
176 * to zero, so that all currently accumulated output in the
177 * output stream is discarded. The output stream can be used again,
178 * reusing the already allocated buffer space.
179 *
180 * @see java.io.ByteArrayInputStream#count
181 */
182 public synchronized void reset() {
183 count = 0;
184 }
185
186 /**
187 * Creates a newly allocated byte array. Its size is the current
188 * size of this output stream and the valid contents of the buffer
189 * have been copied into it.
190 *
191 * @return the current contents of this output stream, as a byte array.
192 * @see java.io.ByteArrayOutputStream#size()
193 */
194 public synchronized byte[] toByteArray() {
195 return Arrays.copyOf(buf, count);
196 }
197
198 /**
199 * Returns the current size of the buffer.
200 *
201 * @return the value of the {@code count} field, which is the number
202 * of valid bytes in this output stream.
203 * @see java.io.ByteArrayOutputStream#count
204 */
205 public synchronized int size() {
206 return count;
207 }
208
209 /**
210 * Converts the buffer's contents into a string decoding bytes using the
211 * default charset. The length of the new {@code String}
212 * is a function of the charset, and hence may not be equal to the
213 * size of the buffer.
214 *
215 * <p> This method always replaces malformed-input and unmappable-character
216 * sequences with the default replacement string for the
217 * default charset. The {@linkplain java.nio.charset.CharsetDecoder}
218 * class should be used when more control over the decoding process is
219 * required.
220 *
221 * @see Charset#defaultCharset()
222 * @return String decoded from the buffer's contents.
223 * @since 1.1
224 */
225 @Override
226 public synchronized String toString() {
227 return new String(buf, 0, count);
228 }
229
230 /**
231 * Converts the buffer's contents into a string by decoding the bytes using
232 * the named {@link Charset charset}.
233 *
234 * <p> This method is equivalent to {@code #toString(charset)} that takes a
235 * {@link Charset charset}.
236 *
237 * <p> An invocation of this method of the form
238 *
239 * {@snippet lang=java :
240 * ByteArrayOutputStream b;
241 * b.toString("UTF-8")
242 * }
243 *
244 * behaves in exactly the same way as the expression
245 *
246 * {@snippet lang=java :
247 * ByteArrayOutputStream b;
248 * b.toString(StandardCharsets.UTF_8)
249 * }
250 *
251 *
252 * @param charsetName the name of a supported
253 * {@link Charset charset}
254 * @return String decoded from the buffer's contents.
255 * @throws UnsupportedEncodingException
256 * If the named charset is not supported
257 * @since 1.1
258 */
259 public synchronized String toString(String charsetName)
260 throws UnsupportedEncodingException
261 {
262 return new String(buf, 0, count, charsetName);
263 }
264
265 /**
266 * Converts the buffer's contents into a string by decoding the bytes using
267 * the specified {@link Charset charset}. The length of the new
268 * {@code String} is a function of the charset, and hence may not be equal
269 * to the length of the byte array.
270 *
271 * <p> This method always replaces malformed-input and unmappable-character
272 * sequences with the charset's default replacement string. The {@link
273 * java.nio.charset.CharsetDecoder} class should be used when more control
274 * over the decoding process is required.
275 *
276 * @param charset the {@linkplain Charset charset}
277 * to be used to decode the {@code bytes}
278 * @return String decoded from the buffer's contents.
279 * @since 10
280 */
281 public synchronized String toString(Charset charset) {
282 return new String(buf, 0, count, charset);
283 }
284
285 /**
286 * Creates a newly allocated string. Its size is the current size of
287 * the output stream and the valid contents of the buffer have been
288 * copied into it. Each character <i>c</i> in the resulting string is
289 * constructed from the corresponding element <i>b</i> in the byte
290 * array such that:
291 * {@snippet lang=java :
292 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
293 * }
294 *
295 * @deprecated This method does not properly convert bytes into characters.
296 * As of JDK 1.1, the preferred way to do this is via the
297 * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
298 * method, which takes an encoding-name or charset argument,
299 * or the {@code toString()} method, which uses the default charset.
300 *
301 * @param hibyte the high byte of each resulting Unicode character.
302 * @return the current contents of the output stream, as a string.
303 * @see java.io.ByteArrayOutputStream#size()
304 * @see java.io.ByteArrayOutputStream#toString(String)
305 * @see java.io.ByteArrayOutputStream#toString()
306 * @see Charset#defaultCharset()
307 */
308 @Deprecated
309 public synchronized String toString(int hibyte) {
310 return new String(buf, hibyte, 0, count);
311 }
312
313 /**
314 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
315 * this class can be called after the stream has been closed without
316 * generating an {@code IOException}.
317 */
318 @Override
319 public void close() throws IOException {
320 }
321
322 }