1 /*
2 * Copyright (c) 1994, 2019, 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 growAtLeastBy = minCapacity - oldCapacity;
99 if (growAtLeastBy > 0) {
100 buf = Arrays.copyOf(buf, ArraysSupport.newCapacity(oldCapacity,
101 growAtLeastBy, oldCapacity));
102 }
103 }
104
105 /**
106 * Writes the specified byte to this {@code ByteArrayOutputStream}.
107 *
108 * @param b the byte to be written.
109 */
110 public synchronized void write(int b) {
111 ensureCapacity(count + 1);
112 buf[count] = (byte) b;
113 count += 1;
114 }
115
116 /**
117 * Writes {@code len} bytes from the specified byte array
118 * starting at offset {@code off} to this {@code ByteArrayOutputStream}.
119 *
120 * @param b the data.
121 * @param off the start offset in the data.
122 * @param len the number of bytes to write.
123 * @throws NullPointerException if {@code b} is {@code null}.
124 * @throws IndexOutOfBoundsException if {@code off} is negative,
125 * {@code len} is negative, or {@code len} is greater than
126 * {@code b.length - off}
127 */
128 public synchronized void write(byte b[], int off, int len) {
129 Objects.checkFromIndexSize(off, len, b.length);
130 ensureCapacity(count + len);
131 System.arraycopy(b, off, buf, count, len);
132 count += len;
133 }
134
135 /**
136 * Writes the complete contents of the specified byte array
137 * to this {@code ByteArrayOutputStream}.
138 *
139 * @apiNote
140 * This method is equivalent to {@link #write(byte[],int,int)
141 * write(b, 0, b.length)}.
142 *
143 * @param b the data.
144 * @throws NullPointerException if {@code b} is {@code null}.
145 * @since 11
146 */
147 public void writeBytes(byte b[]) {
148 write(b, 0, b.length);
149 }
150
151 /**
152 * Writes the complete contents of this {@code ByteArrayOutputStream} to
153 * the specified output stream argument, as if by calling the output
154 * stream's write method using {@code out.write(buf, 0, count)}.
155 *
156 * @param out the output stream to which to write the data.
157 * @throws NullPointerException if {@code out} is {@code null}.
158 * @throws IOException if an I/O error occurs.
159 */
160 public synchronized void writeTo(OutputStream out) throws IOException {
161 out.write(buf, 0, count);
162 }
163
164 /**
165 * Resets the {@code count} field of this {@code ByteArrayOutputStream}
166 * to zero, so that all currently accumulated output in the
167 * output stream is discarded. The output stream can be used again,
168 * reusing the already allocated buffer space.
169 *
170 * @see java.io.ByteArrayInputStream#count
171 */
172 public synchronized void reset() {
173 count = 0;
174 }
175
176 /**
177 * Creates a newly allocated byte array. Its size is the current
178 * size of this output stream and the valid contents of the buffer
179 * have been copied into it.
180 *
181 * @return the current contents of this output stream, as a byte array.
182 * @see java.io.ByteArrayOutputStream#size()
183 */
184 public synchronized byte[] toByteArray() {
185 return Arrays.copyOf(buf, count);
186 }
187
188 /**
189 * Returns the current size of the buffer.
190 *
191 * @return the value of the {@code count} field, which is the number
192 * of valid bytes in this output stream.
193 * @see java.io.ByteArrayOutputStream#count
194 */
195 public synchronized int size() {
196 return count;
197 }
198
199 /**
200 * Converts the buffer's contents into a string decoding bytes using the
201 * platform's default character set. The length of the new {@code String}
202 * is a function of the character set, and hence may not be equal to the
203 * size of the buffer.
204 *
205 * <p> This method always replaces malformed-input and unmappable-character
206 * sequences with the default replacement string for the platform's
207 * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
208 * class should be used when more control over the decoding process is
209 * required.
210 *
211 * @return String decoded from the buffer's contents.
212 * @since 1.1
213 */
214 public synchronized String toString() {
215 return new String(buf, 0, count);
216 }
217
218 /**
219 * Converts the buffer's contents into a string by decoding the bytes using
220 * the named {@link java.nio.charset.Charset charset}.
221 *
222 * <p> This method is equivalent to {@code #toString(charset)} that takes a
223 * {@link java.nio.charset.Charset charset}.
224 *
225 * <p> An invocation of this method of the form
226 *
227 * <pre> {@code
228 * ByteArrayOutputStream b = ...
229 * b.toString("UTF-8")
230 * }
231 * </pre>
232 *
233 * behaves in exactly the same way as the expression
234 *
235 * <pre> {@code
236 * ByteArrayOutputStream b = ...
237 * b.toString(StandardCharsets.UTF_8)
238 * }
239 * </pre>
240 *
241 *
242 * @param charsetName the name of a supported
243 * {@link java.nio.charset.Charset charset}
244 * @return String decoded from the buffer's contents.
245 * @throws UnsupportedEncodingException
246 * If the named charset is not supported
247 * @since 1.1
248 */
249 public synchronized String toString(String charsetName)
250 throws UnsupportedEncodingException
251 {
252 return new String(buf, 0, count, charsetName);
253 }
254
255 /**
256 * Converts the buffer's contents into a string by decoding the bytes using
257 * the specified {@link java.nio.charset.Charset charset}. The length of the new
258 * {@code String} is a function of the charset, and hence may not be equal
259 * to the length of the byte array.
260 *
261 * <p> This method always replaces malformed-input and unmappable-character
262 * sequences with the charset's default replacement string. The {@link
263 * java.nio.charset.CharsetDecoder} class should be used when more control
264 * over the decoding process is required.
265 *
266 * @param charset the {@linkplain java.nio.charset.Charset charset}
267 * to be used to decode the {@code bytes}
268 * @return String decoded from the buffer's contents.
269 * @since 10
270 */
271 public synchronized String toString(Charset charset) {
272 return new String(buf, 0, count, charset);
273 }
274
275 /**
276 * Creates a newly allocated string. Its size is the current size of
277 * the output stream and the valid contents of the buffer have been
278 * copied into it. Each character <i>c</i> in the resulting string is
279 * constructed from the corresponding element <i>b</i> in the byte
280 * array such that:
281 * <blockquote><pre>{@code
282 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
283 * }</pre></blockquote>
284 *
285 * @deprecated This method does not properly convert bytes into characters.
286 * As of JDK 1.1, the preferred way to do this is via the
287 * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
288 * method, which takes an encoding-name or charset argument,
289 * or the {@code toString()} method, which uses the platform's default
290 * character encoding.
291 *
292 * @param hibyte the high byte of each resulting Unicode character.
293 * @return the current contents of the output stream, as a string.
294 * @see java.io.ByteArrayOutputStream#size()
295 * @see java.io.ByteArrayOutputStream#toString(String)
296 * @see java.io.ByteArrayOutputStream#toString()
297 */
298 @Deprecated
299 public synchronized String toString(int hibyte) {
300 return new String(buf, hibyte, 0, count);
301 }
302
303 /**
304 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
305 * this class can be called after the stream has been closed without
306 * generating an {@code IOException}.
307 */
308 public void close() throws IOException {
309 }
310
311 }