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 java.io.IOException; 20 21 /** 22 * Package-protected abstract class that implements the line reading 23 * algorithm used by {@link LineReader}. Line separators are per {@link 24 * java.io.BufferedReader}: line feed, carriage return, or carriage 25 * return followed immediately by a linefeed. 26 * 27 * <p>Subclasses must implement {@link #handleLine}, call {@link #add} 28 * to pass character data, and call {@link #finish} at the end of stream. 29 * 30 * @author Chris Nokleberg 31 * @since 1.0 32 */ 33 abstract class LineBuffer { 34 /** Holds partial line contents. */ 35 private StringBuilder line = new StringBuilder(); 36 /** Whether a line ending with a CR is pending processing. */ 37 private boolean sawReturn; 38 39 /** 40 * Process additional characters from the stream. When a line separator 41 * is found the contents of the line and the line separator itself 42 * are passed to the abstract {@link #handleLine} method. 43 * 44 * @param cbuf the character buffer to process 45 * @param off the offset into the buffer 46 * @param len the number of characters to process 47 * @throws IOException if an I/O error occurs 48 * @see #finish 49 */ add(char[] cbuf, int off, int len)50 protected void add(char[] cbuf, int off, int len) throws IOException { 51 int pos = off; 52 if (sawReturn && len > 0) { 53 // Last call to add ended with a CR; we can handle the line now. 54 if (finishLine(cbuf[pos] == '\n')) { 55 pos++; 56 } 57 } 58 59 int start = pos; 60 for (int end = off + len; pos < end; pos++) { 61 switch (cbuf[pos]) { 62 case '\r': 63 line.append(cbuf, start, pos - start); 64 sawReturn = true; 65 if (pos + 1 < end) { 66 if (finishLine(cbuf[pos + 1] == '\n')) { 67 pos++; 68 } 69 } 70 start = pos + 1; 71 break; 72 73 case '\n': 74 line.append(cbuf, start, pos - start); 75 finishLine(true); 76 start = pos + 1; 77 break; 78 79 default: 80 // do nothing 81 } 82 } 83 line.append(cbuf, start, off + len - start); 84 } 85 86 /** Called when a line is complete. */ finishLine(boolean sawNewline)87 private boolean finishLine(boolean sawNewline) throws IOException { 88 handleLine(line.toString(), sawReturn 89 ? (sawNewline ? "\r\n" : "\r") 90 : (sawNewline ? "\n" : "")); 91 line = new StringBuilder(); 92 sawReturn = false; 93 return sawNewline; 94 } 95 96 /** 97 * Subclasses must call this method after finishing character processing, 98 * in order to ensure that any unterminated line in the buffer is 99 * passed to {@link #handleLine}. 100 * 101 * @throws IOException if an I/O error occurs 102 */ finish()103 protected void finish() throws IOException { 104 if (sawReturn || line.length() > 0) { 105 finishLine(false); 106 } 107 } 108 109 /** 110 * Called for each line found in the character data passed to 111 * {@link #add}. 112 * 113 * @param line a line of text (possibly empty), without any line separators 114 * @param end the line separator; one of {@code "\r"}, {@code "\n"}, 115 * {@code "\r\n"}, or {@code ""} 116 * @throws IOException if an I/O error occurs 117 */ handleLine(String line, String end)118 protected abstract void handleLine(String line, String end) 119 throws IOException; 120 } 121