1 /*
2 * Copyright (c) 1994, 2017, 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 * @exception 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 */
150 public synchronized void write(byte b[], int off, int len) {
151 Objects.checkFromIndexSize(off, len, b.length);
152 ensureCapacity(count + len);
153 System.arraycopy(b, off, buf, count, len);
154 count += len;
155 }
156
157 /**
158 * Writes the complete contents of this byte array output stream to
159 * the specified output stream argument, as if by calling the output
160 * stream's write method using {@code out.write(buf, 0, count)}.
161 *
162 * @param out the output stream to which to write the data.
163 * @exception IOException if an I/O error occurs.
164 */
165 public synchronized void writeTo(OutputStream out) throws IOException {
166 out.write(buf, 0, count);
167 }
168
169 /**
170 * Resets the {@code count} field of this byte array output
171 * stream to zero, so that all currently accumulated output in the
172 * output stream is discarded. The output stream can be used again,
173 * reusing the already allocated buffer space.
174 *
175 * @see java.io.ByteArrayInputStream#count
176 */
177 public synchronized void reset() {
178 count = 0;
179 }
180
181 /**
182 * Creates a newly allocated byte array. Its size is the current
183 * size of this output stream and the valid contents of the buffer
184 * have been copied into it.
185 *
186 * @return the current contents of this output stream, as a byte array.
187 * @see java.io.ByteArrayOutputStream#size()
188 */
189 public synchronized byte[] toByteArray() {
190 return Arrays.copyOf(buf, count);
191 }
192
193 /**
194 * Returns the current size of the buffer.
195 *
196 * @return the value of the {@code count} field, which is the number
197 * of valid bytes in this output stream.
198 * @see java.io.ByteArrayOutputStream#count
199 */
200 public synchronized int size() {
201 return count;
202 }
203
204 /**
205 * Converts the buffer's contents into a string decoding bytes using the
206 * platform's default character set. The length of the new {@code String}
207 * is a function of the character set, and hence may not be equal to the
208 * size of the buffer.
209 *
210 * <p> This method always replaces malformed-input and unmappable-character
211 * sequences with the default replacement string for the platform's
212 * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
213 * class should be used when more control over the decoding process is
214 * required.
215 *
216 * @return String decoded from the buffer's contents.
217 * @since 1.1
218 */
219 public synchronized String toString() {
220 return new String(buf, 0, count);
221 }
222
223 /**
224 * Converts the buffer's contents into a string by decoding the bytes using
225 * the named {@link java.nio.charset.Charset charset}.
226 *
227 * <p> This method is equivalent to {@code #toString(charset)} that takes a
228 * {@link java.nio.charset.Charset charset}.
229 *
230 * <p> An invocation of this method of the form
231 *
232 * <pre> {@code
233 * ByteArrayOutputStream b = ...
234 * b.toString("UTF-8")
235 * }
236 * </pre>
237 *
238 * behaves in exactly the same way as the expression
239 *
240 * <pre> {@code
241 * ByteArrayOutputStream b = ...
242 * b.toString(StandardCharsets.UTF_8)
243 * }
244 * </pre>
245 *
246 *
247 * @param charsetName the name of a supported
248 * {@link java.nio.charset.Charset charset}
249 * @return String decoded from the buffer's contents.
250 * @exception UnsupportedEncodingException
251 * If the named charset is not supported
252 * @since 1.1
253 */
254 public synchronized String toString(String charsetName)
255 throws UnsupportedEncodingException
256 {
257 return new String(buf, 0, count, charsetName);
258 }
259
260 /**
261 * Converts the buffer's contents into a string by decoding the bytes using
262 * the specified {@link java.nio.charset.Charset charset}. The length of the new
263 * {@code String} is a function of the charset, and hence may not be equal
264 * to the length of the byte array.
265 *
266 * <p> This method always replaces malformed-input and unmappable-character
267 * sequences with the charset's default replacement string. The {@link
268 * java.nio.charset.CharsetDecoder} class should be used when more control
269 * over the decoding process is required.
270 *
271 * @param charset the {@linkplain java.nio.charset.Charset charset}
272 * to be used to decode the {@code bytes}
273 * @return String decoded from the buffer's contents.
274 * @since 10
275 */
276 public synchronized String toString(Charset charset) {
277 return new String(buf, 0, count, charset);
278 }
279
280 /**
281 * Creates a newly allocated string. Its size is the current size of
282 * the output stream and the valid contents of the buffer have been
283 * copied into it. Each character <i>c</i> in the resulting string is
284 * constructed from the corresponding element <i>b</i> in the byte
285 * array such that:
286 * <blockquote><pre>{@code
287 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
288 * }</pre></blockquote>
289 *
290 * @deprecated This method does not properly convert bytes into characters.
291 * As of JDK 1.1, the preferred way to do this is via the
292 * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
293 * method, which takes an encoding-name or charset argument,
294 * or the {@code toString()} method, which uses the platform's default
295 * character encoding.
296 *
297 * @param hibyte the high byte of each resulting Unicode character.
298 * @return the current contents of the output stream, as a string.
299 * @see java.io.ByteArrayOutputStream#size()
300 * @see java.io.ByteArrayOutputStream#toString(String)
301 * @see java.io.ByteArrayOutputStream#toString()
302 */
303 @Deprecated
304 public synchronized String toString(int hibyte) {
305 return new String(buf, hibyte, 0, count);
306 }
307
308 /**
309 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
310 * this class can be called after the stream has been closed without
311 * generating an {@code IOException}.
312 */
313 public void close() throws IOException {
314 }
315
316 }