1 /*
2 * Copyright (c) 1994, 2018, 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 /**
33 * This class implements an output stream in which the data is
34 * written into a byte array. The buffer automatically grows as data
35 * is written to it.
36 * The data can be retrieved using {@code toByteArray()} and
37 * {@code toString()}.
38 * <p>
39 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
40 * this class can be called after the stream has been closed without
41 * generating an {@code IOException}.
42 *
43 * @author Arthur van Hoff
44 * @since 1.0
45 */
46
47 public class ByteArrayOutputStream extends OutputStream {
48
49 /**
50 * The buffer where data is stored.
51 */
52 protected byte buf[];
53
54 /**
55 * The number of valid bytes in the buffer.
56 */
57 protected int count;
58
59 /**
60 * Creates a new byte array output stream. The buffer capacity is
61 * initially 32 bytes, though its size increases if necessary.
62 */
63 public ByteArrayOutputStream() {
64 this(32);
65 }
66
67 /**
68 * Creates a new byte array output stream, with a buffer capacity of
69 * the specified size, in bytes.
70 *
71 * @param size the initial size.
72 * @throws IllegalArgumentException if size is negative.
73 */
74 public ByteArrayOutputStream(int size) {
75 if (size < 0) {
76 throw new IllegalArgumentException("Negative initial size: "
77 + size);
78 }
79 buf = new byte[size];
80 }
81
82 /**
83 * Increases the capacity if necessary to ensure that it can hold
84 * at least the number of elements specified by the minimum
85 * capacity argument.
86 *
87 * @param minCapacity the desired minimum capacity
88 * @throws OutOfMemoryError if {@code minCapacity < 0}. This is
89 * interpreted as a request for the unsatisfiably large capacity
90 * {@code (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE)}.
91 */
92 private void ensureCapacity(int minCapacity) {
93 // overflow-conscious code
94 if (minCapacity - buf.length > 0)
95 grow(minCapacity);
96 }
97
98 /**
99 * The maximum size of array to allocate.
100 * Some VMs reserve some header words in an array.
101 * Attempts to allocate larger arrays may result in
102 * OutOfMemoryError: Requested array size exceeds VM limit
103 */
104 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
105
106 /**
107 * Increases the capacity to ensure that it can hold at least the
108 * number of elements specified by the minimum capacity argument.
109 *
110 * @param minCapacity the desired minimum capacity
111 */
112 private void grow(int minCapacity) {
113 // overflow-conscious code
114 int oldCapacity = buf.length;
115 int newCapacity = oldCapacity << 1;
116 if (newCapacity - minCapacity < 0)
117 newCapacity = minCapacity;
118 if (newCapacity - MAX_ARRAY_SIZE > 0)
119 newCapacity = hugeCapacity(minCapacity);
120 buf = Arrays.copyOf(buf, newCapacity);
121 }
122
123 private static int hugeCapacity(int minCapacity) {
124 if (minCapacity < 0) // overflow
125 throw new OutOfMemoryError();
126 return (minCapacity > MAX_ARRAY_SIZE) ?
127 Integer.MAX_VALUE :
128 MAX_ARRAY_SIZE;
129 }
130
131 /**
132 * Writes the specified byte to this byte array output stream.
133 *
134 * @param b the byte to be written.
135 */
136 public synchronized void write(int b) {
137 ensureCapacity(count + 1);
138 buf[count] = (byte) b;
139 count += 1;
140 }
141
142 /**
143 * Writes {@code len} bytes from the specified byte array
144 * starting at offset {@code off} to this byte array output stream.
145 *
146 * @param b the data.
147 * @param off the start offset in the data.
148 * @param len the number of bytes to write.
149 * @throws NullPointerException if {@code b} is {@code null}.
150 * @throws IndexOutOfBoundsException if {@code off} is negative,
151 * {@code len} is negative, or {@code len} is greater than
152 * {@code b.length - off}
153 */
154 public synchronized void write(byte b[], int off, int len) {
155 Objects.checkFromIndexSize(off, len, b.length);
156 ensureCapacity(count + len);
157 System.arraycopy(b, off, buf, count, len);
158 count += len;
159 }
160
161 /**
162 * Writes the complete contents of the specified byte array
163 * to this byte array output stream.
164 *
165 * <p> This method is equivalent to {@link #write(byte[],int,int)
166 * write(b,0,b.length)}.
167 *
168 * @param b the data.
169 * @throws NullPointerException if {@code b} is {@code null}.
170 * @since 11
171 */
172 public void writeBytes(byte b[]) {
173 write(b, 0, b.length);
174 }
175
176 /**
177 * Writes the complete contents of this byte array output stream to
178 * the specified output stream argument, as if by calling the output
179 * stream's write method using {@code out.write(buf, 0, count)}.
180 *
181 * @param out the output stream to which to write the data.
182 * @throws NullPointerException if {@code out} is {@code null}.
183 * @throws IOException if an I/O error occurs.
184 */
185 public synchronized void writeTo(OutputStream out) throws IOException {
186 out.write(buf, 0, count);
187 }
188
189 /**
190 * Resets the {@code count} field of this byte array output
191 * stream to zero, so that all currently accumulated output in the
192 * output stream is discarded. The output stream can be used again,
193 * reusing the already allocated buffer space.
194 *
195 * @see java.io.ByteArrayInputStream#count
196 */
197 public synchronized void reset() {
198 count = 0;
199 }
200
201 /**
202 * Creates a newly allocated byte array. Its size is the current
203 * size of this output stream and the valid contents of the buffer
204 * have been copied into it.
205 *
206 * @return the current contents of this output stream, as a byte array.
207 * @see java.io.ByteArrayOutputStream#size()
208 */
209 public synchronized byte[] toByteArray() {
210 return Arrays.copyOf(buf, count);
211 }
212
213 /**
214 * Returns the current size of the buffer.
215 *
216 * @return the value of the {@code count} field, which is the number
217 * of valid bytes in this output stream.
218 * @see java.io.ByteArrayOutputStream#count
219 */
220 public synchronized int size() {
221 return count;
222 }
223
224 /**
225 * Converts the buffer's contents into a string decoding bytes using the
226 * platform's default character set. The length of the new {@code String}
227 * is a function of the character set, and hence may not be equal to the
228 * size of the buffer.
229 *
230 * <p> This method always replaces malformed-input and unmappable-character
231 * sequences with the default replacement string for the platform's
232 * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
233 * class should be used when more control over the decoding process is
234 * required.
235 *
236 * @return String decoded from the buffer's contents.
237 * @since 1.1
238 */
239 public synchronized String toString() {
240 return new String(buf, 0, count);
241 }
242
243 /**
244 * Converts the buffer's contents into a string by decoding the bytes using
245 * the named {@link java.nio.charset.Charset charset}.
246 *
247 * <p> This method is equivalent to {@code #toString(charset)} that takes a
248 * {@link java.nio.charset.Charset charset}.
249 *
250 * <p> An invocation of this method of the form
251 *
252 * <pre> {@code
253 * ByteArrayOutputStream b = ...
254 * b.toString("UTF-8")
255 * }
256 * </pre>
257 *
258 * behaves in exactly the same way as the expression
259 *
260 * <pre> {@code
261 * ByteArrayOutputStream b = ...
262 * b.toString(StandardCharsets.UTF_8)
263 * }
264 * </pre>
265 *
266 *
267 * @param charsetName the name of a supported
268 * {@link java.nio.charset.Charset charset}
269 * @return String decoded from the buffer's contents.
270 * @throws UnsupportedEncodingException
271 * If the named charset is not supported
272 * @since 1.1
273 */
274 public synchronized String toString(String charsetName)
275 throws UnsupportedEncodingException
276 {
277 return new String(buf, 0, count, charsetName);
278 }
279
280 /**
281 * Converts the buffer's contents into a string by decoding the bytes using
282 * the specified {@link java.nio.charset.Charset charset}. The length of the new
283 * {@code String} is a function of the charset, and hence may not be equal
284 * to the length of the byte array.
285 *
286 * <p> This method always replaces malformed-input and unmappable-character
287 * sequences with the charset's default replacement string. The {@link
288 * java.nio.charset.CharsetDecoder} class should be used when more control
289 * over the decoding process is required.
290 *
291 * @param charset the {@linkplain java.nio.charset.Charset charset}
292 * to be used to decode the {@code bytes}
293 * @return String decoded from the buffer's contents.
294 * @since 10
295 */
296 public synchronized String toString(Charset charset) {
297 return new String(buf, 0, count, charset);
298 }
299
300 /**
301 * Creates a newly allocated string. Its size is the current size of
302 * the output stream and the valid contents of the buffer have been
303 * copied into it. Each character <i>c</i> in the resulting string is
304 * constructed from the corresponding element <i>b</i> in the byte
305 * array such that:
306 * <blockquote><pre>{@code
307 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
308 * }</pre></blockquote>
309 *
310 * @deprecated This method does not properly convert bytes into characters.
311 * As of JDK 1.1, the preferred way to do this is via the
312 * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
313 * method, which takes an encoding-name or charset argument,
314 * or the {@code toString()} method, which uses the platform's default
315 * character encoding.
316 *
317 * @param hibyte the high byte of each resulting Unicode character.
318 * @return the current contents of the output stream, as a string.
319 * @see java.io.ByteArrayOutputStream#size()
320 * @see java.io.ByteArrayOutputStream#toString(String)
321 * @see java.io.ByteArrayOutputStream#toString()
322 */
323 @Deprecated
324 public synchronized String toString(int hibyte) {
325 return new String(buf, hibyte, 0, count);
326 }
327
328 /**
329 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
330 * this class can be called after the stream has been closed without
331 * generating an {@code IOException}.
332 */
333 public void close() throws IOException {
334 }
335
336 }