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.util.Arrays;
29 import java.util.Objects;
30
31 /**
32 * A {@code ByteArrayInputStream} contains
33 * an internal buffer that contains bytes that
34 * may be read from the stream. An internal
35 * counter keeps track of the next byte to
36 * be supplied by the {@code read} method.
37 * <p>
38 * Closing a {@code ByteArrayInputStream} has no effect. The methods in
39 * this class can be called after the stream has been closed without
40 * generating an {@code IOException}.
41 *
42 * @author Arthur van Hoff
43 * @see java.io.StringBufferInputStream
44 * @since 1.0
45 */
46 public class ByteArrayInputStream extends InputStream {
47
48 /**
49 * An array of bytes that was provided
50 * by the creator of the stream. Elements {@code buf[0]}
51 * through {@code buf[count-1]} are the
52 * only bytes that can ever be read from the
53 * stream; element {@code buf[pos]} is
54 * the next byte to be read.
55 */
56 protected byte buf[];
57
58 /**
59 * The index of the next character to read from the input stream buffer.
60 * This value should always be nonnegative
61 * and not larger than the value of {@code count}.
62 * The next byte to be read from the input stream buffer
63 * will be {@code buf[pos]}.
64 */
65 protected int pos;
66
67 /**
68 * The currently marked position in the stream.
69 * ByteArrayInputStream objects are marked at position zero by
70 * default when constructed. They may be marked at another
71 * position within the buffer by the {@code mark()} method.
72 * The current buffer position is set to this point by the
73 * {@code reset()} method.
74 * <p>
75 * If no mark has been set, then the value of mark is the offset
76 * passed to the constructor (or 0 if the offset was not supplied).
77 *
78 * @since 1.1
79 */
80 protected int mark = 0;
81
82 /**
83 * The index one greater than the last valid character in the input
84 * stream buffer.
85 * This value should always be nonnegative
86 * and not larger than the length of {@code buf}.
87 * It is one greater than the position of
88 * the last byte within {@code buf} that
89 * can ever be read from the input stream buffer.
90 */
91 protected int count;
92
93 /**
94 * Creates a {@code ByteArrayInputStream}
95 * so that it uses {@code buf} as its
96 * buffer array.
97 * The buffer array is not copied.
98 * The initial value of {@code pos}
99 * is {@code 0} and the initial value
100 * of {@code count} is the length of
101 * {@code buf}.
102 *
103 * @param buf the input buffer.
104 */
105 public ByteArrayInputStream(byte buf[]) {
106 this.buf = buf;
107 this.pos = 0;
108 this.count = buf.length;
109 }
110
111 /**
112 * Creates {@code ByteArrayInputStream}
113 * that uses {@code buf} as its
114 * buffer array. The initial value of {@code pos}
115 * is {@code offset} and the initial value
116 * of {@code count} is the minimum of {@code offset+length}
117 * and {@code buf.length}.
118 * The buffer array is not copied. The buffer's mark is
119 * set to the specified offset.
120 *
121 * @param buf the input buffer.
122 * @param offset the offset in the buffer of the first byte to read.
123 * @param length the maximum number of bytes to read from the buffer.
124 */
125 public ByteArrayInputStream(byte buf[], int offset, int length) {
126 this.buf = buf;
127 this.pos = offset;
128 this.count = Math.min(offset + length, buf.length);
129 this.mark = offset;
130 }
131
132 /**
133 * Reads the next byte of data from this input stream. The value
134 * byte is returned as an {@code int} in the range
135 * {@code 0} to {@code 255}. If no byte is available
136 * because the end of the stream has been reached, the value
137 * {@code -1} is returned.
138 * <p>
139 * This {@code read} method
140 * cannot block.
141 *
142 * @return the next byte of data, or {@code -1} if the end of the
143 * stream has been reached.
144 */
145 @Override
146 public synchronized int read() {
147 return (pos < count) ? (buf[pos++] & 0xff) : -1;
148 }
149
150 /**
151 * Reads up to {@code len} bytes of data into an array of bytes
152 * from this input stream.
153 * If {@code pos} equals {@code count},
154 * then {@code -1} is returned to indicate
155 * end of file. Otherwise, the number {@code k}
156 * of bytes read is equal to the smaller of
157 * {@code len} and {@code count-pos}.
158 * If {@code k} is positive, then bytes
159 * {@code buf[pos]} through {@code buf[pos+k-1]}
160 * are copied into {@code b[off]} through
161 * {@code b[off+k-1]} in the manner performed
162 * by {@code System.arraycopy}. The
163 * value {@code k} is added into {@code pos}
164 * and {@code k} is returned.
165 * <p>
166 * This {@code read} method cannot block.
167 *
168 * @param b the buffer into which the data is read.
169 * @param off the start offset in the destination array {@code b}
170 * @param len the maximum number of bytes read.
171 * @return the total number of bytes read into the buffer, or
172 * {@code -1} if there is no more data because the end of
173 * the stream has been reached.
174 * @throws NullPointerException If {@code b} is {@code null}.
175 * @throws IndexOutOfBoundsException If {@code off} is negative,
176 * {@code len} is negative, or {@code len} is greater than
177 * {@code b.length - off}
178 */
179 @Override
180 public synchronized int read(byte b[], int off, int len) {
181 Objects.checkFromIndexSize(off, len, b.length);
182
183 if (pos >= count) {
184 return -1;
185 }
186
187 int avail = count - pos;
188 if (len > avail) {
189 len = avail;
190 }
191 if (len <= 0) {
192 return 0;
193 }
194 System.arraycopy(buf, pos, b, off, len);
195 pos += len;
196 return len;
197 }
198
199 @Override
200 public synchronized byte[] readAllBytes() {
201 byte[] result = Arrays.copyOfRange(buf, pos, count);
202 pos = count;
203 return result;
204 }
205
206 @Override
207 public int readNBytes(byte[] b, int off, int len) {
208 int n = read(b, off, len);
209 return n == -1 ? 0 : n;
210 }
211
212 @Override
213 public synchronized long transferTo(OutputStream out) throws IOException {
214 int len = count - pos;
215 out.write(buf, pos, len);
216 pos = count;
217 return len;
218 }
219
220 /**
221 * Skips {@code n} bytes of input from this input stream. Fewer
222 * bytes might be skipped if the end of the input stream is reached.
223 * The actual number {@code k}
224 * of bytes to be skipped is equal to the smaller
225 * of {@code n} and {@code count-pos}.
226 * The value {@code k} is added into {@code pos}
227 * and {@code k} is returned.
228 *
229 * @param n the number of bytes to be skipped.
230 * @return the actual number of bytes skipped.
231 */
232 @Override
233 public synchronized long skip(long n) {
234 long k = count - pos;
235 if (n < k) {
236 k = n < 0 ? 0 : n;
237 }
238
239 pos += k;
240 return k;
241 }
242
243 /**
244 * Returns the number of remaining bytes that can be read (or skipped over)
245 * from this input stream.
246 * <p>
247 * The value returned is {@code count - pos},
248 * which is the number of bytes remaining to be read from the input buffer.
249 *
250 * @return the number of remaining bytes that can be read (or skipped
251 * over) from this input stream without blocking.
252 */
253 @Override
254 public synchronized int available() {
255 return count - pos;
256 }
257
258 /**
259 * Tests if this {@code InputStream} supports mark/reset. The
260 * {@code markSupported} method of {@code ByteArrayInputStream}
261 * always returns {@code true}.
262 *
263 * @since 1.1
264 */
265 @Override
266 public boolean markSupported() {
267 return true;
268 }
269
270 /**
271 * Set the current marked position in the stream.
272 * ByteArrayInputStream objects are marked at position zero by
273 * default when constructed. They may be marked at another
274 * position within the buffer by this method.
275 * <p>
276 * If no mark has been set, then the value of the mark is the
277 * offset passed to the constructor (or 0 if the offset was not
278 * supplied).
279 *
280 * <p> Note: The {@code readAheadLimit} for this class
281 * has no meaning.
282 *
283 * @since 1.1
284 */
285 @Override
286 public void mark(int readAheadLimit) {
287 mark = pos;
288 }
289
290 /**
291 * Resets the buffer to the marked position. The marked position
292 * is 0 unless another position was marked or an offset was specified
293 * in the constructor.
294 */
295 @Override
296 public synchronized void reset() {
297 pos = mark;
298 }
299
300 /**
301 * Closing a {@code ByteArrayInputStream} has no effect. The methods in
302 * this class can be called after the stream has been closed without
303 * generating an {@code IOException}.
304 */
305 @Override
306 public void close() throws IOException {
307 }
308
309 }