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 1.1
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 */
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 }