1/*
2 * Copyright (c) 1996, 2005, 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 * This class implements a character buffer that can be used as a
30 * character-input stream.
31 *
32 * @author      Herb Jellinek
33 * @since       JDK1.1
34 */
35public class CharArrayReader extends Reader {
36    /** The character buffer. */
37    protected char buf[];
38
39    /** The current buffer position. */
40    protected int pos;
41
42    /** The position of mark in buffer. */
43    protected int markedPos = 0;
44
45    /**
46     *  The index of the end of this buffer.  There is not valid
47     *  data at or beyond this index.
48     */
49    protected int count;
50
51    /**
52     * Creates a CharArrayReader from the specified array of chars.
53     * @param buf       Input buffer (not copied)
54     */
55    public CharArrayReader(char buf[]) {
56        this.buf = buf;
57        this.pos = 0;
58        this.count = buf.length;
59    }
60
61    /**
62     * Creates a CharArrayReader from the specified array of chars.
63     *
64     * <p> The resulting reader will start reading at the given
65     * <tt>offset</tt>.  The total number of <tt>char</tt> values that can be
66     * read from this reader will be either <tt>length</tt> or
67     * <tt>buf.length-offset</tt>, whichever is smaller.
68     *
69     * @throws IllegalArgumentException
70     *         If <tt>offset</tt> is negative or greater than
71     *         <tt>buf.length</tt>, or if <tt>length</tt> is negative, or if
72     *         the sum of these two values is negative.
73     *
74     * @param buf       Input buffer (not copied)
75     * @param offset    Offset of the first char to read
76     * @param length    Number of chars to read
77     */
78    public CharArrayReader(char buf[], int offset, int length) {
79        if ((offset < 0) || (offset > buf.length) || (length < 0) ||
80            ((offset + length) < 0)) {
81            throw new IllegalArgumentException();
82        }
83        this.buf = buf;
84        this.pos = offset;
85        this.count = Math.min(offset + length, buf.length);
86        this.markedPos = offset;
87    }
88
89    /** Checks to make sure that the stream has not been closed */
90    private void ensureOpen() throws IOException {
91        if (buf == null)
92            throw new IOException("Stream closed");
93    }
94
95    /**
96     * Reads a single character.
97     *
98     * @exception   IOException  If an I/O error occurs
99     */
100    public int read() throws IOException {
101        synchronized (lock) {
102            ensureOpen();
103            if (pos >= count)
104                return -1;
105            else
106                return buf[pos++];
107        }
108    }
109
110    /**
111     * Reads characters into a portion of an array.
112     * @param b  Destination buffer
113     * @param off  Offset at which to start storing characters
114     * @param len   Maximum number of characters to read
115     * @return  The actual number of characters read, or -1 if
116     *          the end of the stream has been reached
117     *
118     * @exception   IOException  If an I/O error occurs
119     */
120    public int read(char b[], int off, int len) throws IOException {
121        synchronized (lock) {
122            ensureOpen();
123            if ((off < 0) || (off > b.length) || (len < 0) ||
124                ((off + len) > b.length) || ((off + len) < 0)) {
125                throw new IndexOutOfBoundsException();
126            } else if (len == 0) {
127                return 0;
128            }
129
130            if (pos >= count) {
131                return -1;
132            }
133
134            int avail = count - pos;
135            if (len > avail) {
136                len = avail;
137            }
138            if (len <= 0) {
139                return 0;
140            }
141            System.arraycopy(buf, pos, b, off, len);
142            pos += len;
143            return len;
144        }
145    }
146
147    /**
148     * Skips characters.  Returns the number of characters that were skipped.
149     *
150     * <p>The <code>n</code> parameter may be negative, even though the
151     * <code>skip</code> method of the {@link Reader} superclass throws
152     * an exception in this case. If <code>n</code> is negative, then
153     * this method does nothing and returns <code>0</code>.
154     *
155     * @param n The number of characters to skip
156     * @return       The number of characters actually skipped
157     * @exception  IOException If the stream is closed, or an I/O error occurs
158     */
159    public long skip(long n) throws IOException {
160        synchronized (lock) {
161            ensureOpen();
162
163            long avail = count - pos;
164            if (n > avail) {
165                n = avail;
166            }
167            if (n < 0) {
168                return 0;
169            }
170            pos += n;
171            return n;
172        }
173    }
174
175    /**
176     * Tells whether this stream is ready to be read.  Character-array readers
177     * are always ready to be read.
178     *
179     * @exception  IOException  If an I/O error occurs
180     */
181    public boolean ready() throws IOException {
182        synchronized (lock) {
183            ensureOpen();
184            return (count - pos) > 0;
185        }
186    }
187
188    /**
189     * Tells whether this stream supports the mark() operation, which it does.
190     */
191    public boolean markSupported() {
192        return true;
193    }
194
195    /**
196     * Marks the present position in the stream.  Subsequent calls to reset()
197     * will reposition the stream to this point.
198     *
199     * @param  readAheadLimit  Limit on the number of characters that may be
200     *                         read while still preserving the mark.  Because
201     *                         the stream's input comes from a character array,
202     *                         there is no actual limit; hence this argument is
203     *                         ignored.
204     *
205     * @exception  IOException  If an I/O error occurs
206     */
207    public void mark(int readAheadLimit) throws IOException {
208        synchronized (lock) {
209            ensureOpen();
210            markedPos = pos;
211        }
212    }
213
214    /**
215     * Resets the stream to the most recent mark, or to the beginning if it has
216     * never been marked.
217     *
218     * @exception  IOException  If an I/O error occurs
219     */
220    public void reset() throws IOException {
221        synchronized (lock) {
222            ensureOpen();
223            pos = markedPos;
224        }
225    }
226
227    /**
228     * Closes the stream and releases any system resources associated with
229     * it.  Once the stream has been closed, further read(), ready(),
230     * mark(), reset(), or skip() invocations will throw an IOException.
231     * Closing a previously closed stream has no effect.
232     */
233    public void close() {
234        buf = null;
235    }
236}
237