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1: /* 2: * LineInputStream.java 3: * Copyright (C) 2002 The Free Software Foundation 4: * 5: * This file is part of GNU inetlib, a library. 6: * 7: * GNU inetlib is free software; you can redistribute it and/or modify 8: * it under the terms of the GNU General Public License as published by 9: * the Free Software Foundation; either version 2 of the License, or 10: * (at your option) any later version. 11: * 12: * GNU inetlib is distributed in the hope that it will be useful, 13: * but WITHOUT ANY WARRANTY; without even the implied warranty of 14: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15: * GNU General Public License for more details. 16: * 17: * You should have received a copy of the GNU General Public License 18: * along with this library; if not, write to the Free Software 19: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 20: * 21: * Linking this library statically or dynamically with other modules is 22: * making a combined work based on this library. Thus, the terms and 23: * conditions of the GNU General Public License cover the whole 24: * combination. 25: * 26: * As a special exception, the copyright holders of this library give you 27: * permission to link this library with independent modules to produce an 28: * executable, regardless of the license terms of these independent 29: * modules, and to copy and distribute the resulting executable under 30: * terms of your choice, provided that you also meet, for each linked 31: * independent module, the terms and conditions of the license of that 32: * module. An independent module is a module which is not derived from 33: * or based on this library. If you modify this library, you may extend 34: * this exception to your version of the library, but you are not 35: * obliged to do so. If you do not wish to do so, delete this 36: * exception statement from your version. 37: */ 38: 39: package gnu.inet.util; 40: 41: import java.io.ByteArrayOutputStream; 42: import java.io.FilterInputStream; 43: import java.io.InputStream; 44: import java.io.IOException; 45: 46: /** 47: * An input stream that can read lines of input. 48: * 49: * @author <a href="mailto:dog@gnu.org">Chris Burdess</a> 50: */ 51: public class LineInputStream 52: extends FilterInputStream 53: { 54: 55: /* 56: * Line buffer. 57: */ 58: private ByteArrayOutputStream buf; 59: 60: /* 61: * Encoding to use when translating bytes to characters. 62: */ 63: private String encoding; 64: 65: /* 66: * End-of-stream flag. 67: */ 68: private boolean eof; 69: 70: /** 71: * Whether we can use block reads. 72: */ 73: private final boolean blockReads; 74: 75: /** 76: * Constructor using the US-ASCII character encoding. 77: * @param in the underlying input stream 78: */ 79: public LineInputStream(InputStream in) 80: { 81: this(in, "US-ASCII"); 82: } 83: 84: /** 85: * Constructor. 86: * @param in the underlying input stream 87: * @param encoding the character encoding to use 88: */ 89: public LineInputStream(InputStream in, String encoding) 90: { 91: super(in); 92: buf = new ByteArrayOutputStream(); 93: this.encoding = encoding; 94: eof = false; 95: blockReads = in.markSupported(); 96: } 97: 98: /** 99: * Read a line of input. 100: */ 101: public String readLine() 102: throws IOException 103: { 104: if (eof) 105: { 106: return null; 107: } 108: do 109: { 110: if (blockReads) 111: { 112: // Use mark and reset to read chunks of bytes 113: final int MIN_LENGTH = 1024; 114: int len, pos; 115: 116: len = in.available(); 117: len = (len < MIN_LENGTH) ? MIN_LENGTH : len; 118: byte[] b = new byte[len]; 119: in.mark(len); 120: // Read into buffer b 121: len = in.read(b, 0, len); 122: // Handle EOF 123: if (len == -1) 124: { 125: eof = true; 126: if (buf.size() == 0) 127: { 128: return null; 129: } 130: else 131: { 132: // We don't care about resetting buf 133: return buf.toString(encoding); 134: } 135: } 136: // Get index of LF in b 137: pos = indexOf(b, len, (byte) 0x0a); 138: if (pos != -1) 139: { 140: // Write pos bytes to buf 141: buf.write(b, 0, pos); 142: // Reset stream, and read pos + 1 bytes 143: in.reset(); 144: pos += 1; 145: while (pos > 0) 146: { 147: len = in.read(b, 0, pos); 148: pos = (len == -1) ? -1 : pos - len; 149: } 150: // Return line 151: String ret = buf.toString(encoding); 152: buf.reset(); 153: return ret; 154: } 155: else 156: { 157: // Append everything to buf and fall through to re-read. 158: buf.write(b, 0, len); 159: } 160: } 161: else 162: { 163: // We must use character reads in order not to read too much 164: // from the underlying stream. 165: int c = in.read(); 166: switch (c) 167: { 168: case -1: 169: eof = true; 170: if (buf.size() == 0) 171: { 172: return null; 173: } 174: // Fall through and return contents of buffer. 175: case 0x0a: // LF 176: String ret = buf.toString(encoding); 177: buf.reset(); 178: return ret; 179: default: 180: buf.write(c); 181: } 182: } 183: } 184: while (true); 185: } 186: 187: private int indexOf(byte[] b, int len, byte c) 188: { 189: for (int pos = 0; pos < len; pos++) 190: { 191: if (b[pos] == c) 192: { 193: return pos; 194: } 195: } 196: return -1; 197: } 198: 199: }