1 /*
2 * Copyright (c) 1996, 2011, 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 /**
30 * A buffered character-input stream that keeps track of line numbers. This
31 * class defines methods {@link #setLineNumber(int)} and {@link
32 * #getLineNumber()} for setting and getting the current line number
33 * respectively.
34 *
35 * <p> By default, line numbering begins at 0. This number increments at every
36 * <a href="#lt">line terminator</a> as the data is read, and can be changed
37 * with a call to {@code setLineNumber(int)}. Note however, that
38 * {@code setLineNumber(int)} does not actually change the current position in
39 * the stream; it only changes the value that will be returned by
40 * {@code getLineNumber()}.
41 *
42 * <p> A line is considered to be <a id="lt">terminated</a> by any one of a
43 * line feed ('\n'), a carriage return ('\r'), or a carriage return followed
44 * immediately by a linefeed.
45 *
46 * @author Mark Reinhold
47 * @since 1.1
48 */
49
50 public class LineNumberReader extends BufferedReader {
51
52 /** The current line number */
53 private int lineNumber = 0;
54
55 /** The line number of the mark, if any */
56 private int markedLineNumber; // Defaults to 0
57
58 /** If the next character is a line feed, skip it */
59 private boolean skipLF;
60
61 /** The skipLF flag when the mark was set */
62 private boolean markedSkipLF;
63
64 /**
65 * Create a new line-numbering reader, using the default input-buffer
66 * size.
67 *
68 * @param in
69 * A Reader object to provide the underlying stream
70 */
71 public LineNumberReader(Reader in) {
72 super(in);
73 }
74
75 /**
76 * Create a new line-numbering reader, reading characters into a buffer of
77 * the given size.
78 *
79 * @param in
80 * A Reader object to provide the underlying stream
81 *
82 * @param sz
83 * An int specifying the size of the buffer
84 */
85 public LineNumberReader(Reader in, int sz) {
86 super(in, sz);
87 }
88
89 /**
90 * Set the current line number.
91 *
92 * @param lineNumber
93 * An int specifying the line number
94 *
95 * @see #getLineNumber
96 */
97 public void setLineNumber(int lineNumber) {
98 this.lineNumber = lineNumber;
99 }
100
101 /**
102 * Get the current line number.
103 *
104 * @return The current line number
105 *
106 * @see #setLineNumber
107 */
108 public int getLineNumber() {
109 return lineNumber;
110 }
111
112 /**
113 * Read a single character. <a href="#lt">Line terminators</a> are
114 * compressed into single newline ('\n') characters. Whenever a line
115 * terminator is read the current line number is incremented.
116 *
117 * @return The character read, or -1 if the end of the stream has been
118 * reached
119 *
120 * @throws IOException
121 * If an I/O error occurs
122 */
123 @SuppressWarnings("fallthrough")
124 public int read() throws IOException {
125 synchronized (lock) {
126 int c = super.read();
127 if (skipLF) {
128 if (c == '\n')
129 c = super.read();
130 skipLF = false;
131 }
132 switch (c) {
133 case '\r':
134 skipLF = true;
135 case '\n': /* Fall through */
136 lineNumber++;
137 return '\n';
138 }
139 return c;
140 }
141 }
142
143 /**
144 * Read characters into a portion of an array. Whenever a <a
145 * href="#lt">line terminator</a> is read the current line number is
146 * incremented.
147 *
148 * @param cbuf
149 * Destination buffer
150 *
151 * @param off
152 * Offset at which to start storing characters
153 *
154 * @param len
155 * Maximum number of characters to read
156 *
157 * @return The number of bytes read, or -1 if the end of the stream has
158 * already been reached
159 *
160 * @throws IOException
161 * If an I/O error occurs
162 *
163 * @throws IndexOutOfBoundsException {@inheritDoc}
164 */
165 @SuppressWarnings("fallthrough")
166 public int read(char[] cbuf, int off, int len) throws IOException {
167 synchronized (lock) {
168 int n = super.read(cbuf, off, len);
169
170 for (int i = off; i < off + n; i++) {
171 int c = cbuf[i];
172 if (skipLF) {
173 skipLF = false;
174 if (c == '\n')
175 continue;
176 }
177 switch (c) {
178 case '\r':
179 skipLF = true;
180 case '\n': /* Fall through */
181 lineNumber++;
182 break;
183 }
184 }
185
186 return n;
187 }
188 }
189
190 /**
191 * Read a line of text. Whenever a <a href="#lt">line terminator</a> is
192 * read the current line number is incremented.
193 *
194 * @return A String containing the contents of the line, not including
195 * any <a href="#lt">line termination characters</a>, or
196 * {@code null} if the end of the stream has been reached
197 *
198 * @throws IOException
199 * If an I/O error occurs
200 */
201 public String readLine() throws IOException {
202 synchronized (lock) {
203 String l = super.readLine(skipLF);
204 skipLF = false;
205 if (l != null)
206 lineNumber++;
207 return l;
208 }
209 }
210
211 /** Maximum skip-buffer size */
212 private static final int maxSkipBufferSize = 8192;
213
214 /** Skip buffer, null until allocated */
215 private char[] skipBuffer = null;
216
217 /**
218 * Skip characters.
219 *
220 * @param n
221 * The number of characters to skip
222 *
223 * @return The number of characters actually skipped
224 *
225 * @throws IOException
226 * If an I/O error occurs
227 *
228 * @throws IllegalArgumentException
229 * If {@code n} is negative
230 */
231 public long skip(long n) throws IOException {
232 if (n < 0)
233 throw new IllegalArgumentException("skip() value is negative");
234 int nn = (int) Math.min(n, maxSkipBufferSize);
235 synchronized (lock) {
236 if ((skipBuffer == null) || (skipBuffer.length < nn))
237 skipBuffer = new char[nn];
238 long r = n;
239 while (r > 0) {
240 int nc = read(skipBuffer, 0, (int) Math.min(r, nn));
241 if (nc == -1)
242 break;
243 r -= nc;
244 }
245 return n - r;
246 }
247 }
248
249 /**
250 * Mark the present position in the stream. Subsequent calls to reset()
251 * will attempt to reposition the stream to this point, and will also reset
252 * the line number appropriately.
253 *
254 * @param readAheadLimit
255 * Limit on the number of characters that may be read while still
256 * preserving the mark. After reading this many characters,
257 * attempting to reset the stream may fail.
258 *
259 * @throws IOException
260 * If an I/O error occurs
261 */
262 public void mark(int readAheadLimit) throws IOException {
263 synchronized (lock) {
264 super.mark(readAheadLimit);
265 markedLineNumber = lineNumber;
266 markedSkipLF = skipLF;
267 }
268 }
269
270 /**
271 * Reset the stream to the most recent mark.
272 *
273 * @throws IOException
274 * If the stream has not been marked, or if the mark has been
275 * invalidated
276 */
277 public void reset() throws IOException {
278 synchronized (lock) {
279 super.reset();
280 lineNumber = markedLineNumber;
281 skipLF = markedSkipLF;
282 }
283 }
284
285 }