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 synchronized void writeTo(OutputStream out) throws IOException {
163 out.write(buf, 0, count);
164 }
165
166 /**
167 * Resets the {@code count} field of this {@code ByteArrayOutputStream}
168 * to zero, so that all currently accumulated output in the
169 * output stream is discarded. The output stream can be used again,
170 * reusing the already allocated buffer space.
171 *
172 * @see java.io.ByteArrayInputStream#count
173 */
174 public synchronized void reset() {
175 count = 0;
176 }
177
178 /**
179 * Creates a newly allocated byte array. Its size is the current
180 * size of this output stream and the valid contents of the buffer
181 * have been copied into it.
182 *
183 * @return the current contents of this output stream, as a byte array.
184 * @see java.io.ByteArrayOutputStream#size()
185 */
186 public synchronized byte[] toByteArray() {
187 return Arrays.copyOf(buf, count);
188 }
189
190 /**
191 * Returns the current size of the buffer.
192 *
193 * @return the value of the {@code count} field, which is the number
194 * of valid bytes in this output stream.
195 * @see java.io.ByteArrayOutputStream#count
196 */
197 public synchronized int size() {
198 return count;
199 }
200
201 /**
202 * Converts the buffer's contents into a string decoding bytes using the
203 * default charset. The length of the new {@code String}
204 * is a function of the charset, and hence may not be equal to the
205 * size of the buffer.
206 *
207 * <p> This method always replaces malformed-input and unmappable-character
208 * sequences with the default replacement string for the
209 * default charset. The {@linkplain java.nio.charset.CharsetDecoder}
210 * class should be used when more control over the decoding process is
211 * required.
212 *
213 * @see Charset#defaultCharset()
214 * @return String decoded from the buffer's contents.
215 * @since 1.1
216 */
217 @Override
218 public synchronized String toString() {
219 return new String(buf, 0, count);
220 }
221
222 /**
223 * Converts the buffer's contents into a string by decoding the bytes using
224 * the named {@link Charset charset}.
225 *
226 * <p> This method is equivalent to {@code #toString(charset)} that takes a
227 * {@link Charset charset}.
228 *
229 * <p> An invocation of this method of the form
230 *
231 * {@snippet lang=java :
232 * ByteArrayOutputStream b;
233 * b.toString("UTF-8")
234 * }
235 *
236 * behaves in exactly the same way as the expression
237 *
238 * {@snippet lang=java :
239 * ByteArrayOutputStream b;
240 * b.toString(StandardCharsets.UTF_8)
241 * }
242 *
243 *
244 * @param charsetName the name of a supported
245 * {@link Charset charset}
246 * @return String decoded from the buffer's contents.
247 * @throws UnsupportedEncodingException
248 * If the named charset is not supported
249 * @since 1.1
250 */
251 public synchronized String toString(String charsetName)
252 throws UnsupportedEncodingException
253 {
254 return new String(buf, 0, count, charsetName);
255 }
256
257 /**
258 * Converts the buffer's contents into a string by decoding the bytes using
259 * the specified {@link Charset charset}. The length of the new
260 * {@code String} is a function of the charset, and hence may not be equal
261 * to the length of the byte array.
262 *
263 * <p> This method always replaces malformed-input and unmappable-character
264 * sequences with the charset's default replacement string. The {@link
265 * java.nio.charset.CharsetDecoder} class should be used when more control
266 * over the decoding process is required.
267 *
268 * @param charset the {@linkplain Charset charset}
269 * to be used to decode the {@code bytes}
270 * @return String decoded from the buffer's contents.
271 * @since 10
272 */
273 public synchronized String toString(Charset charset) {
274 return new String(buf, 0, count, charset);
275 }
276
277 /**
278 * Creates a newly allocated string. Its size is the current size of
279 * the output stream and the valid contents of the buffer have been
280 * copied into it. Each character <i>c</i> in the resulting string is
281 * constructed from the corresponding element <i>b</i> in the byte
282 * array such that:
283 * {@snippet lang=java :
284 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
285 * }
286 *
287 * @deprecated This method does not properly convert bytes into characters.
288 * As of JDK 1.1, the preferred way to do this is via the
289 * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
290 * method, which takes an encoding-name or charset argument,
291 * or the {@code toString()} method, which uses the default charset.
292 *
293 * @param hibyte the high byte of each resulting Unicode character.
294 * @return the current contents of the output stream, as a string.
295 * @see java.io.ByteArrayOutputStream#size()
296 * @see java.io.ByteArrayOutputStream#toString(String)
297 * @see java.io.ByteArrayOutputStream#toString()
298 * @see Charset#defaultCharset()
299 */
300 @Deprecated
301 public synchronized String toString(int hibyte) {
302 return new String(buf, hibyte, 0, count);
303 }
304
305 /**
306 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
307 * this class can be called after the stream has been closed without
308 * generating an {@code IOException}.
309 */
310 @Override
311 public void close() throws IOException {
312 }
313
314 }