1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
4 *
5 *
6 *
7 *
8 *
9 *
10 *
11 *
12 *
13 *
14 *
15 *
16 *
17 *
18 *
19 *
20 *
21 *
22 *
23 *
24 */
25
26 package java.io;
27
28 /**
29 * A <code>ByteArrayInputStream</code> contains
30 * an internal buffer that contains bytes that
31 * may be read from the stream. An internal
32 * counter keeps track of the next byte to
33 * be supplied by the <code>read</code> method.
34 * <p>
35 * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
36 * this class can be called after the stream has been closed without
37 * generating an <tt>IOException</tt>.
38 *
39 * @author Arthur van Hoff
40 * @see java.io.StringBufferInputStream
41 * @since JDK1.0
42 */
43 public
44 class ByteArrayInputStream extends InputStream {
45
46 /**
47 * An array of bytes that was provided
48 * by the creator of the stream. Elements <code>buf[0]</code>
49 * through <code>buf[count-1]</code> are the
50 * only bytes that can ever be read from the
51 * stream; element <code>buf[pos]</code> is
52 * the next byte to be read.
53 */
54 protected byte buf[];
55
56 /**
57 * The index of the next character to read from the input stream buffer.
58 * This value should always be nonnegative
59 * and not larger than the value of <code>count</code>.
60 * The next byte to be read from the input stream buffer
61 * will be <code>buf[pos]</code>.
62 */
63 protected int pos;
64
65 /**
66 * The currently marked position in the stream.
67 * ByteArrayInputStream objects are marked at position zero by
68 * default when constructed. They may be marked at another
69 * position within the buffer by the <code>mark()</code> method.
70 * The current buffer position is set to this point by the
71 * <code>reset()</code> method.
72 * <p>
73 * If no mark has been set, then the value of mark is the offset
74 * passed to the constructor (or 0 if the offset was not supplied).
75 *
76 * @since JDK1.1
77 */
78 protected int mark = 0;
79
80 /**
81 * The index one greater than the last valid character in the input
82 * stream buffer.
83 * This value should always be nonnegative
84 * and not larger than the length of <code>buf</code>.
85 * It is one greater than the position of
86 * the last byte within <code>buf</code> that
87 * can ever be read from the input stream buffer.
88 */
89 protected int count;
90
91 /**
92 * Creates a <code>ByteArrayInputStream</code>
93 * so that it uses <code>buf</code> as its
94 * buffer array.
95 * The buffer array is not copied.
96 * The initial value of <code>pos</code>
97 * is <code>0</code> and the initial value
98 * of <code>count</code> is the length of
99 * <code>buf</code>.
100 *
101 * @param buf the input buffer.
102 */
103 public ByteArrayInputStream(byte buf[]) {
104 this.buf = buf;
105 this.pos = 0;
106 this.count = buf.length;
107 }
108
109 /**
110 * Creates <code>ByteArrayInputStream</code>
111 * that uses <code>buf</code> as its
112 * buffer array. The initial value of <code>pos</code>
113 * is <code>offset</code> and the initial value
114 * of <code>count</code> is the minimum of <code>offset+length</code>
115 * and <code>buf.length</code>.
116 * The buffer array is not copied. The buffer's mark is
117 * set to the specified offset.
118 *
119 * @param buf the input buffer.
120 * @param offset the offset in the buffer of the first byte to read.
121 * @param length the maximum number of bytes to read from the buffer.
122 */
123 public ByteArrayInputStream(byte buf[], int offset, int length) {
124 this.buf = buf;
125 this.pos = offset;
126 this.count = Math.min(offset + length, buf.length);
127 this.mark = offset;
128 }
129
130 /**
131 * Reads the next byte of data from this input stream. The value
132 * byte is returned as an <code>int</code> in the range
133 * <code>0</code> to <code>255</code>. If no byte is available
134 * because the end of the stream has been reached, the value
135 * <code>-1</code> is returned.
136 * <p>
137 * This <code>read</code> method
138 * cannot block.
139 *
140 * @return the next byte of data, or <code>-1</code> if the end of the
141 * stream has been reached.
142 */
143 public synchronized int read() {
144 return (pos < count) ? (buf[pos++] & 0xff) : -1;
145 }
146
147 /**
148 * Reads up to <code>len</code> bytes of data into an array of bytes
149 * from this input stream.
150 * If <code>pos</code> equals <code>count</code>,
151 * then <code>-1</code> is returned to indicate
152 * end of file. Otherwise, the number <code>k</code>
153 * of bytes read is equal to the smaller of
154 * <code>len</code> and <code>count-pos</code>.
155 * If <code>k</code> is positive, then bytes
156 * <code>buf[pos]</code> through <code>buf[pos+k-1]</code>
157 * are copied into <code>b[off]</code> through
158 * <code>b[off+k-1]</code> in the manner performed
159 * by <code>System.arraycopy</code>. The
160 * value <code>k</code> is added into <code>pos</code>
161 * and <code>k</code> is returned.
162 * <p>
163 * This <code>read</code> method cannot block.
164 *
165 * @param b the buffer into which the data is read.
166 * @param off the start offset in the destination array <code>b</code>
167 * @param len the maximum number of bytes read.
168 * @return the total number of bytes read into the buffer, or
169 * <code>-1</code> if there is no more data because the end of
170 * the stream has been reached.
171 * @exception NullPointerException If <code>b</code> is <code>null</code>.
172 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
173 * <code>len</code> is negative, or <code>len</code> is greater than
174 * <code>b.length - off</code>
175 */
176 public synchronized int read(byte b[], int off, int len) {
177 if (b == null) {
178 throw new NullPointerException();
179 } else if (off < 0 || len < 0 || len > b.length - off) {
180 throw new IndexOutOfBoundsException();
181 }
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 /**
200 * Skips <code>n</code> bytes of input from this input stream. Fewer
201 * bytes might be skipped if the end of the input stream is reached.
202 * The actual number <code>k</code>
203 * of bytes to be skipped is equal to the smaller
204 * of <code>n</code> and <code>count-pos</code>.
205 * The value <code>k</code> is added into <code>pos</code>
206 * and <code>k</code> is returned.
207 *
208 * @param n the number of bytes to be skipped.
209 * @return the actual number of bytes skipped.
210 */
211 public synchronized long skip(long n) {
212 long k = count - pos;
213 if (n < k) {
214 k = n < 0 ? 0 : n;
215 }
216
217 pos += k;
218 return k;
219 }
220
221 /**
222 * Returns the number of remaining bytes that can be read (or skipped over)
223 * from this input stream.
224 * <p>
225 * The value returned is <code>count - pos</code>,
226 * which is the number of bytes remaining to be read from the input buffer.
227 *
228 * @return the number of remaining bytes that can be read (or skipped
229 * over) from this input stream without blocking.
230 */
231 public synchronized int available() {
232 return count - pos;
233 }
234
235 /**
236 * Tests if this <code>InputStream</code> supports mark/reset. The
237 * <code>markSupported</code> method of <code>ByteArrayInputStream</code>
238 * always returns <code>true</code>.
239 *
240 * @since JDK1.1
241 */
242 public boolean markSupported() {
243 return true;
244 }
245
246 /**
247 * Set the current marked position in the stream.
248 * ByteArrayInputStream objects are marked at position zero by
249 * default when constructed. They may be marked at another
250 * position within the buffer by this method.
251 * <p>
252 * If no mark has been set, then the value of the mark is the
253 * offset passed to the constructor (or 0 if the offset was not
254 * supplied).
255 *
256 * <p> Note: The <code>readAheadLimit</code> for this class
257 * has no meaning.
258 *
259 * @since JDK1.1
260 */
261 public void mark(int readAheadLimit) {
262 mark = pos;
263 }
264
265 /**
266 * Resets the buffer to the marked position. The marked position
267 * is 0 unless another position was marked or an offset was specified
268 * in the constructor.
269 */
270 public synchronized void reset() {
271 pos = mark;
272 }
273
274 /**
275 * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
276 * this class can be called after the stream has been closed without
277 * generating an <tt>IOException</tt>.
278 */
279 public void close() throws IOException {
280 }
281
282 }
283