1 /* 2 * Copyright (C) 2007 Google Inc. 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 2009.09.15 <b>tentative</b> 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 */ 50 @SuppressWarnings("fallthrough") add(char[] cbuf, int off, int len)51 protected void add(char[] cbuf, int off, int len) throws IOException { 52 int pos = off; 53 if (sawReturn && len > 0) { 54 // Last call to add ended with a CR; we can handle the line now. 55 if (finishLine(cbuf[pos] == '\n')) { 56 pos++; 57 } 58 } 59 60 int start = pos; 61 for (int end = off + len; pos < end; pos++) { 62 switch (cbuf[pos]) { 63 case '\r': 64 line.append(cbuf, start, pos - start); 65 sawReturn = true; 66 if (pos + 1 < end) { 67 if (finishLine(cbuf[pos + 1] == '\n')) { 68 pos++; 69 } 70 } 71 start = pos + 1; 72 break; 73 74 case '\n': 75 line.append(cbuf, start, pos - start); 76 finishLine(true); 77 start = pos + 1; 78 break; 79 } 80 } 81 line.append(cbuf, start, off + len - start); 82 } 83 84 /** Called when a line is complete. */ finishLine(boolean sawNewline)85 private boolean finishLine(boolean sawNewline) throws IOException { 86 handleLine(line.toString(), sawReturn 87 ? (sawNewline ? "\r\n" : "\r") 88 : (sawNewline ? "\n" : "")); 89 line = new StringBuilder(); 90 sawReturn = false; 91 return sawNewline; 92 } 93 94 /** 95 * Subclasses must call this method after finishing character processing, 96 * in order to ensure that any unterminated line in the buffer is 97 * passed to {@link #handleLine}. 98 * 99 * @throws IOException if an I/O error occurs 100 */ finish()101 protected void finish() throws IOException { 102 if (sawReturn || line.length() > 0) { 103 finishLine(false); 104 } 105 } 106 107 /** 108 * Called for each line found in the character data passed to 109 * {@link #add}. 110 * 111 * @param line a line of text (possibly empty), without any line separators 112 * @param end the line separator; one of {@code "\r"}, {@code "\n"}, 113 * {@code "\r\n"}, or {@code ""} 114 * @throws IOException if an I/O error occurs 115 */ handleLine(String line, String end)116 protected abstract void handleLine(String line, String end) 117 throws IOException; 118 } 119