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
26package 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 */
43public
44class 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&nbsp;- 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