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1: /* LineInputStream.java -- 2: Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 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: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.net; 40: 41: import java.io.BufferedInputStream; 42: import java.io.ByteArrayOutputStream; 43: import java.io.FilterInputStream; 44: import java.io.IOException; 45: import java.io.InputStream; 46: 47: /** 48: * An input stream that can read lines of input. 49: * 50: * @author Chris Burdess (dog@gnu.org) 51: */ 52: public class LineInputStream 53: extends FilterInputStream 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: // If it is already buffered, additional buffering gains nothing. 96: blockReads = !(in instanceof BufferedInputStream) && in.markSupported(); 97: } 98: 99: /** 100: * Read a line of input. 101: */ 102: public String readLine() 103: throws IOException 104: { 105: if (eof) 106: { 107: return null; 108: } 109: do 110: { 111: if (blockReads) 112: { 113: // Use mark and reset to read chunks of bytes 114: final int MAX_LENGTH = 1024; 115: int len, pos; 116: 117: len = in.available(); 118: if (len == 0 || len > MAX_LENGTH) 119: len = MAX_LENGTH; 120: byte[] b = new byte[len]; 121: in.mark(len); 122: // Read into buffer b 123: len = in.read(b, 0, len); 124: // Handle EOF 125: if (len == -1) 126: { 127: eof = true; 128: if (buf.size() == 0) 129: { 130: return null; 131: } 132: else 133: { 134: // We don't care about resetting buf 135: return buf.toString(encoding); 136: } 137: } 138: // Get index of LF in b 139: pos = indexOf(b, len, (byte) 0x0a); 140: if (pos != -1) 141: { 142: // Write pos bytes to buf 143: buf.write(b, 0, pos); 144: // Reset stream, and read pos + 1 bytes 145: in.reset(); 146: pos += 1; 147: while (pos > 0) 148: { 149: len = in.read(b, 0, pos); 150: pos = (len == -1) ? -1 : pos - len; 151: } 152: // Return line 153: String ret = buf.toString(encoding); 154: buf.reset(); 155: return ret; 156: } 157: else 158: { 159: // Append everything to buf and fall through to re-read. 160: buf.write(b, 0, len); 161: } 162: } 163: else 164: { 165: // We must use character reads in order not to read too much 166: // from the underlying stream. 167: int c = in.read(); 168: switch (c) 169: { 170: case -1: 171: eof = true; 172: if (buf.size() == 0) 173: { 174: return null; 175: } 176: // Fall through and return contents of buffer. 177: case 0x0a: // LF 178: String ret = buf.toString(encoding); 179: buf.reset(); 180: return ret; 181: default: 182: buf.write(c); 183: } 184: } 185: } 186: while (true); 187: } 188: 189: private int indexOf(byte[] b, int len, byte c) 190: { 191: for (int pos = 0; pos < len; pos++) 192: { 193: if (b[pos] == c) 194: { 195: return pos; 196: } 197: } 198: return -1; 199: } 200: }