1 /*
2 * Copyright (c) 1994, 2013, 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.util.Arrays;
29
30 /**
31 * This class implements an output stream in which the data is
32 * written into a byte array. The buffer automatically grows as data
33 * is written to it.
34 * The data can be retrieved using <code>toByteArray()</code> and
35 * <code>toString()</code>.
36 * <p>
37 * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in
38 * this class can be called after the stream has been closed without
39 * generating an <tt>IOException</tt>.
40 *
41 * @author Arthur van Hoff
42 * @since JDK1.0
43 */
44
45 public class ByteArrayOutputStream extends OutputStream {
46
47 /**
48 * The buffer where data is stored.
49 */
50 protected byte buf[];
51
52 /**
53 * The number of valid bytes in the buffer.
54 */
55 protected int count;
56
57 /**
58 * Creates a new byte array output stream. The buffer capacity is
59 * initially 32 bytes, though its size increases if necessary.
60 */
61 public ByteArrayOutputStream() {
62 this(32);
63 }
64
65 /**
66 * Creates a new byte array output stream, with a buffer capacity of
67 * the specified size, in bytes.
68 *
69 * @param size the initial size.
70 * @exception IllegalArgumentException if size is negative.
71 */
72 public ByteArrayOutputStream(int size) {
73 if (size < 0) {
74 throw new IllegalArgumentException("Negative initial size: "
75 + size);
76 }
77 buf = new byte[size];
78 }
79
80 /**
81 * Increases the capacity if necessary to ensure that it can hold
82 * at least the number of elements specified by the minimum
83 * capacity argument.
84 *
85 * @param minCapacity the desired minimum capacity
86 * @throws OutOfMemoryError if {@code minCapacity < 0}. This is
87 * interpreted as a request for the unsatisfiably large capacity
88 * {@code (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE)}.
89 */
90 private void ensureCapacity(int minCapacity) {
91 // overflow-conscious code
92 if (minCapacity - buf.length > 0)
93 grow(minCapacity);
94 }
95
96 /**
97 * Increases the capacity to ensure that it can hold at least the
98 * number of elements specified by the minimum capacity argument.
99 *
100 * @param minCapacity the desired minimum capacity
101 */
102 private void grow(int minCapacity) {
103 // overflow-conscious code
104 int oldCapacity = buf.length;
105 int newCapacity = oldCapacity << 1;
106 if (newCapacity - minCapacity < 0)
107 newCapacity = minCapacity;
108 if (newCapacity < 0) {
109 if (minCapacity < 0) // overflow
110 throw new OutOfMemoryError();
111 newCapacity = Integer.MAX_VALUE;
112 }
113 buf = Arrays.copyOf(buf, newCapacity);
114 }
115
116 /**
117 * Writes the specified byte to this byte array output stream.
118 *
119 * @param b the byte to be written.
120 */
121 public synchronized void write(int b) {
122 ensureCapacity(count + 1);
123 buf[count] = (byte) b;
124 count += 1;
125 }
126
127 /**
128 * Writes <code>len</code> bytes from the specified byte array
129 * starting at offset <code>off</code> to this byte array output stream.
130 *
131 * @param b the data.
132 * @param off the start offset in the data.
133 * @param len the number of bytes to write.
134 */
135 public synchronized void write(byte b[], int off, int len) {
136 if ((off < 0) || (off > b.length) || (len < 0) ||
137 ((off + len) - b.length > 0)) {
138 throw new IndexOutOfBoundsException();
139 }
140 ensureCapacity(count + len);
141 System.arraycopy(b, off, buf, count, len);
142 count += len;
143 }
144
145 /**
146 * Writes the complete contents of this byte array output stream to
147 * the specified output stream argument, as if by calling the output
148 * stream's write method using <code>out.write(buf, 0, count)</code>.
149 *
150 * @param out the output stream to which to write the data.
151 * @exception IOException if an I/O error occurs.
152 */
153 public synchronized void writeTo(OutputStream out) throws IOException {
154 out.write(buf, 0, count);
155 }
156
157 /**
158 * Resets the <code>count</code> field of this byte array output
159 * stream to zero, so that all currently accumulated output in the
160 * output stream is discarded. The output stream can be used again,
161 * reusing the already allocated buffer space.
162 *
163 * @see java.io.ByteArrayInputStream#count
164 */
165 public synchronized void reset() {
166 count = 0;
167 }
168
169 /**
170 * Creates a newly allocated byte array. Its size is the current
171 * size of this output stream and the valid contents of the buffer
172 * have been copied into it.
173 *
174 * @return the current contents of this output stream, as a byte array.
175 * @see java.io.ByteArrayOutputStream#size()
176 */
177 public synchronized byte toByteArray()[] {
178 return Arrays.copyOf(buf, count);
179 }
180
181 /**
182 * Returns the current size of the buffer.
183 *
184 * @return the value of the <code>count</code> field, which is the number
185 * of valid bytes in this output stream.
186 * @see java.io.ByteArrayOutputStream#count
187 */
188 public synchronized int size() {
189 return count;
190 }
191
192 /**
193 * Converts the buffer's contents into a string decoding bytes using the
194 * platform's default character set. The length of the new <tt>String</tt>
195 * is a function of the character set, and hence may not be equal to the
196 * size of the buffer.
197 *
198 * <p> This method always replaces malformed-input and unmappable-character
199 * sequences with the default replacement string for the platform's
200 * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
201 * class should be used when more control over the decoding process is
202 * required.
203 *
204 * @return String decoded from the buffer's contents.
205 * @since JDK1.1
206 */
207 public synchronized String toString() {
208 return new String(buf, 0, count);
209 }
210
211 /**
212 * Converts the buffer's contents into a string by decoding the bytes using
213 * the named {@link java.nio.charset.Charset charset}. The length of the new
214 * <tt>String</tt> is a function of the charset, and hence may not be equal
215 * to the length of the byte array.
216 *
217 * <p> This method always replaces malformed-input and unmappable-character
218 * sequences with this charset's default replacement string. The {@link
219 * java.nio.charset.CharsetDecoder} class should be used when more control
220 * over the decoding process is required.
221 *
222 * @param charsetName the name of a supported
223 * {@link java.nio.charset.Charset charset}
224 * @return String decoded from the buffer's contents.
225 * @exception UnsupportedEncodingException
226 * If the named charset is not supported
227 * @since JDK1.1
228 */
229 public synchronized String toString(String charsetName)
230 throws UnsupportedEncodingException
231 {
232 return new String(buf, 0, count, charsetName);
233 }
234
235 /**
236 * Creates a newly allocated string. Its size is the current size of
237 * the output stream and the valid contents of the buffer have been
238 * copied into it. Each character <i>c</i> in the resulting string is
239 * constructed from the corresponding element <i>b</i> in the byte
240 * array such that:
241 * <blockquote><pre>
242 * c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
243 * </pre></blockquote>
244 *
245 * @deprecated This method does not properly convert bytes into characters.
246 * As of JDK 1.1, the preferred way to do this is via the
247 * <code>toString(String enc)</code> method, which takes an encoding-name
248 * argument, or the <code>toString()</code> method, which uses the
249 * platform's default character encoding.
250 *
251 * @param hibyte the high byte of each resulting Unicode character.
252 * @return the current contents of the output stream, as a string.
253 * @see java.io.ByteArrayOutputStream#size()
254 * @see java.io.ByteArrayOutputStream#toString(String)
255 * @see java.io.ByteArrayOutputStream#toString()
256 */
257 @Deprecated
258 public synchronized String toString(int hibyte) {
259 return new String(buf, hibyte, 0, count);
260 }
261
262 /**
263 * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in
264 * this class can be called after the stream has been closed without
265 * generating an <tt>IOException</tt>.
266 */
267 public void close() throws IOException {
268 }
269
270 }