1 /* 2 * Copyright (c) 1996, 2019, 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 */ LineNumberReader(Reader in)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 */ LineNumberReader(Reader in, int sz)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 */ setLineNumber(int lineNumber)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 */ getLineNumber()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") read()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") read(char cbuf[], int off, int len)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 */ readLine()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 */ skip(long n)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 */ mark(int readAheadLimit)262 public void mark(int readAheadLimit) throws IOException { 263 synchronized (lock) { 264 // If the most recently read character is '\r', then increment the 265 // read ahead limit as in this case if the next character is '\n', 266 // two characters would actually be read by the next read(). 267 if (skipLF) 268 readAheadLimit++; 269 super.mark(readAheadLimit); 270 markedLineNumber = lineNumber; 271 markedSkipLF = skipLF; 272 } 273 } 274 275 /** 276 * Reset the stream to the most recent mark. 277 * 278 * @throws IOException 279 * If the stream has not been marked, or if the mark has been 280 * invalidated 281 */ reset()282 public void reset() throws IOException { 283 synchronized (lock) { 284 super.reset(); 285 lineNumber = markedLineNumber; 286 skipLF = markedSkipLF; 287 } 288 } 289 290 } 291