Source for gnu.java.net.LineInputStream

   1: /* LineInputStream.java --
   2:    Copyright (C) 2002, 2003, 2004, 2005, 2006  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.IOException;
  44: import java.io.InputStream;
  45: 
  46: /**
  47:  * An input stream that can read lines of input.
  48:  *
  49:  * @author Chris Burdess (dog@gnu.org)
  50:  */
  51: public class LineInputStream
  52:   extends InputStream
  53: {
  54: 
  55:   /**
  56:    * The underlying input stream.
  57:    */
  58:   protected InputStream in;
  59: 
  60:   /*
  61:    * Line buffer.
  62:    */
  63:   private ByteArrayOutputStream buf;
  64: 
  65:   /*
  66:    * Encoding to use when translating bytes to characters.
  67:    */
  68:   private String encoding;
  69: 
  70:   /*
  71:    * End-of-stream flag.
  72:    */
  73:   private boolean eof;
  74: 
  75:   /**
  76:    * Whether we can use block reads.
  77:    */
  78:   private final boolean blockReads;
  79: 
  80:   /**
  81:    * Constructor using the US-ASCII character encoding.
  82:    * @param in the underlying input stream
  83:    */
  84:   public LineInputStream(InputStream in)
  85:   {
  86:     this(in, "US-ASCII");
  87:   }
  88: 
  89:   /**
  90:    * Constructor.
  91:    * @param in the underlying input stream
  92:    * @param encoding the character encoding to use
  93:    */
  94:   public LineInputStream(InputStream in, String encoding)
  95:   {
  96:     this.in = in;
  97:     buf = new ByteArrayOutputStream();
  98:     this.encoding = encoding;
  99:     eof = false;
 100:     // If it is already buffered, additional buffering gains nothing.
 101:     blockReads = !(in instanceof BufferedInputStream) && in.markSupported();
 102:   }
 103: 
 104:   public int read()
 105:     throws IOException
 106:   {
 107:     return in.read();
 108:   }
 109: 
 110:   public int read(byte[] buf)
 111:     throws IOException
 112:   {
 113:     return in.read(buf);
 114:   }
 115: 
 116:   public int read(byte[] buf, int off, int len)
 117:     throws IOException
 118:   {
 119:     return in.read(buf, off, len);
 120:   }
 121: 
 122:   /**
 123:    * Read a line of input.
 124:    */
 125:   public String readLine()
 126:     throws IOException
 127:   {
 128:     if (eof)
 129:       {
 130:         return null;
 131:       }
 132:     do
 133:       {
 134:         if (blockReads)
 135:           {
 136:             // Use mark and reset to read chunks of bytes
 137:             final int MAX_LENGTH = 1024;
 138:             int len, pos;
 139: 
 140:             len = in.available();
 141:             if (len == 0 || len > MAX_LENGTH)
 142:               len = MAX_LENGTH;
 143:             byte[] b = new byte[len];
 144:             in.mark(len);
 145:             // Read into buffer b
 146:             len = in.read(b, 0, len);
 147:             // Handle EOF
 148:             if (len == -1)
 149:               {
 150:                 eof = true;
 151:                 if (buf.size() == 0)
 152:                   {
 153:                     return null;
 154:                   }
 155:                 else
 156:                   {
 157:                     // We don't care about resetting buf
 158:                     return buf.toString(encoding);
 159:                   }
 160:               }
 161:             // Get index of LF in b
 162:             pos = indexOf(b, len, (byte) 0x0a);
 163:             if (pos != -1)
 164:               {
 165:                 // Write pos bytes to buf
 166:                 buf.write(b, 0, pos);
 167:                 // Reset stream, and read pos + 1 bytes
 168:                 in.reset();
 169:                 pos += 1;
 170:                 while (pos > 0)
 171:                   {
 172:                     len = in.read(b, 0, pos);
 173:                     pos = (len == -1) ? -1 : pos - len;
 174:                   }
 175:                 // Return line
 176:                 String ret = buf.toString(encoding);
 177:                 buf.reset();
 178:                 return ret;
 179:               }
 180:             else
 181:               {
 182:                 // Append everything to buf and fall through to re-read.
 183:                 buf.write(b, 0, len);
 184:               }
 185:           }
 186:         else
 187:           {
 188:             // We must use character reads in order not to read too much
 189:             // from the underlying stream.
 190:             int c = in.read();
 191:             switch (c)
 192:               {
 193:               case -1:
 194:                 eof = true;
 195:                 if (buf.size() == 0)
 196:                   {
 197:                     return null;
 198:                   }
 199:                 // Fall through and return contents of buffer.
 200:               case 0x0a:                // LF
 201:                 String ret = buf.toString(encoding);
 202:                 buf.reset();
 203:                 return ret;
 204:               default:
 205:                 buf.write(c);
 206:               }
 207:           }
 208:       }
 209:     while (true);
 210:   }
 211: 
 212:   private int indexOf(byte[] b, int len, byte c)
 213:   {
 214:     for (int pos = 0; pos < len; pos++)
 215:       {
 216:         if (b[pos] == c)
 217:           {
 218:             return pos;
 219:           }
 220:       }
 221:     return -1;
 222:   }
 223: }