1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.io; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 21 import com.google.common.annotations.Beta; 22 23 import java.io.IOException; 24 import java.io.Reader; 25 import java.nio.CharBuffer; 26 import java.util.LinkedList; 27 import java.util.Queue; 28 29 /** 30 * A class for reading lines of text. Provides the same functionality 31 * as {@link java.io.BufferedReader#readLine()} but for all {@link Readable} 32 * objects, not just instances of {@link Reader}. 33 * 34 * @author Chris Nokleberg 35 * @since 1.0 36 */ 37 @Beta 38 public final class LineReader { 39 private final Readable readable; 40 private final Reader reader; 41 private final char[] buf = new char[0x1000]; // 4K 42 private final CharBuffer cbuf = CharBuffer.wrap(buf); 43 44 private final Queue<String> lines = new LinkedList<String>(); 45 private final LineBuffer lineBuf = new LineBuffer() { 46 @Override protected void handleLine(String line, String end) { 47 lines.add(line); 48 } 49 }; 50 51 /** 52 * Creates a new instance that will read lines from the given 53 * {@code Readable} object. 54 */ 55 public LineReader(Readable readable) { 56 this.readable = checkNotNull(readable); 57 this.reader = (readable instanceof Reader) ? (Reader) readable : null; 58 } 59 60 /** 61 * Reads a line of text. A line is considered to be terminated by any 62 * one of a line feed ({@code '\n'}), a carriage return 63 * ({@code '\r'}), or a carriage return followed immediately by a linefeed 64 * ({@code "\r\n"}). 65 * 66 * @return a {@code String} containing the contents of the line, not 67 * including any line-termination characters, or {@code null} if the 68 * end of the stream has been reached. 69 * @throws IOException if an I/O error occurs 70 */ 71 public String readLine() throws IOException { 72 while (lines.peek() == null) { 73 cbuf.clear(); 74 // The default implementation of Reader#read(CharBuffer) allocates a 75 // temporary char[], so we call Reader#read(char[], int, int) instead. 76 int read = (reader != null) 77 ? reader.read(buf, 0, buf.length) 78 : readable.read(cbuf); 79 if (read == -1) { 80 lineBuf.finish(); 81 break; 82 } 83 lineBuf.add(buf, 0, read); 84 } 85 return lines.poll(); 86 } 87 } 88
