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 
26 package 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  */
35 public 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      */
CharArrayReader(char buf[])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      */
CharArrayReader(char buf[], int offset, int length)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 */
ensureOpen()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      */
read()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      */
read(char b[], int off, int len)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             // BEGIN Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow.
134             int avail = count - pos;
135             if (len > avail) {
136                 len = avail;
137             }
138             // END Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow.
139             if (len <= 0) {
140                 return 0;
141             }
142             System.arraycopy(buf, pos, b, off, len);
143             pos += len;
144             return len;
145         }
146     }
147 
148     /**
149      * Skips characters.  Returns the number of characters that were skipped.
150      *
151      * <p>The <code>n</code> parameter may be negative, even though the
152      * <code>skip</code> method of the {@link Reader} superclass throws
153      * an exception in this case. If <code>n</code> is negative, then
154      * this method does nothing and returns <code>0</code>.
155      *
156      * @param n The number of characters to skip
157      * @return       The number of characters actually skipped
158      * @exception  IOException If the stream is closed, or an I/O error occurs
159      */
skip(long n)160     public long skip(long n) throws IOException {
161         synchronized (lock) {
162             ensureOpen();
163             // BEGIN Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow.
164             long avail = count - pos;
165             if (n > avail) {
166                 n = avail;
167             }
168             // END Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow.
169             if (n < 0) {
170                 return 0;
171             }
172             pos += n;
173             return n;
174         }
175     }
176 
177     /**
178      * Tells whether this stream is ready to be read.  Character-array readers
179      * are always ready to be read.
180      *
181      * @exception  IOException  If an I/O error occurs
182      */
ready()183     public boolean ready() throws IOException {
184         synchronized (lock) {
185             ensureOpen();
186             return (count - pos) > 0;
187         }
188     }
189 
190     /**
191      * Tells whether this stream supports the mark() operation, which it does.
192      */
markSupported()193     public boolean markSupported() {
194         return true;
195     }
196 
197     /**
198      * Marks the present position in the stream.  Subsequent calls to reset()
199      * will reposition the stream to this point.
200      *
201      * @param  readAheadLimit  Limit on the number of characters that may be
202      *                         read while still preserving the mark.  Because
203      *                         the stream's input comes from a character array,
204      *                         there is no actual limit; hence this argument is
205      *                         ignored.
206      *
207      * @exception  IOException  If an I/O error occurs
208      */
mark(int readAheadLimit)209     public void mark(int readAheadLimit) throws IOException {
210         synchronized (lock) {
211             ensureOpen();
212             markedPos = pos;
213         }
214     }
215 
216     /**
217      * Resets the stream to the most recent mark, or to the beginning if it has
218      * never been marked.
219      *
220      * @exception  IOException  If an I/O error occurs
221      */
reset()222     public void reset() throws IOException {
223         synchronized (lock) {
224             ensureOpen();
225             pos = markedPos;
226         }
227     }
228 
229     /**
230      * Closes the stream and releases any system resources associated with
231      * it.  Once the stream has been closed, further read(), ready(),
232      * mark(), reset(), or skip() invocations will throw an IOException.
233      * Closing a previously closed stream has no effect.
234      */
close()235     public void close() {
236         buf = null;
237     }
238 }
239