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            if (pos + len > count) {
134                len = count - pos;
135            }
136            if (len <= 0) {
137                return 0;
138            }
139            System.arraycopy(buf, pos, b, off, len);
140            pos += len;
141            return len;
142        }
143    }
144
145    /**
146     * Skips characters.  Returns the number of characters that were skipped.
147     *
148     * <p>The <code>n</code> parameter may be negative, even though the
149     * <code>skip</code> method of the {@link Reader} superclass throws
150     * an exception in this case. If <code>n</code> is negative, then
151     * this method does nothing and returns <code>0</code>.
152     *
153     * @param n The number of characters to skip
154     * @return       The number of characters actually skipped
155     * @exception  IOException If the stream is closed, or an I/O error occurs
156     */
157    public long skip(long n) throws IOException {
158        synchronized (lock) {
159            ensureOpen();
160            if (pos + n > count) {
161                n = count - pos;
162            }
163            if (n < 0) {
164                return 0;
165            }
166            pos += n;
167            return n;
168        }
169    }
170
171    /**
172     * Tells whether this stream is ready to be read.  Character-array readers
173     * are always ready to be read.
174     *
175     * @exception  IOException  If an I/O error occurs
176     */
177    public boolean ready() throws IOException {
178        synchronized (lock) {
179            ensureOpen();
180            return (count - pos) > 0;
181        }
182    }
183
184    /**
185     * Tells whether this stream supports the mark() operation, which it does.
186     */
187    public boolean markSupported() {
188        return true;
189    }
190
191    /**
192     * Marks the present position in the stream.  Subsequent calls to reset()
193     * will reposition the stream to this point.
194     *
195     * @param  readAheadLimit  Limit on the number of characters that may be
196     *                         read while still preserving the mark.  Because
197     *                         the stream's input comes from a character array,
198     *                         there is no actual limit; hence this argument is
199     *                         ignored.
200     *
201     * @exception  IOException  If an I/O error occurs
202     */
203    public void mark(int readAheadLimit) throws IOException {
204        synchronized (lock) {
205            ensureOpen();
206            markedPos = pos;
207        }
208    }
209
210    /**
211     * Resets the stream to the most recent mark, or to the beginning if it has
212     * never been marked.
213     *
214     * @exception  IOException  If an I/O error occurs
215     */
216    public void reset() throws IOException {
217        synchronized (lock) {
218            ensureOpen();
219            pos = markedPos;
220        }
221    }
222
223    /**
224     * Closes the stream and releases any system resources associated with
225     * it.  Once the stream has been closed, further read(), ready(),
226     * mark(), reset(), or skip() invocations will throw an IOException.
227     * Closing a previously closed stream has no effect.
228     */
229    public void close() {
230        buf = null;
231    }
232}
233