libjava/classpath/java/io/DataInputStream.java

   1 /* DataInputStream.java -- FilteredInputStream that implements DataInput
   2    Copyright (C) 1998, 1999, 2000, 2001, 2003, 2005, 2008
   3    Free Software Foundation
   4
   5 This file is part of GNU Classpath.
   6
   7 GNU Classpath 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, or (at your option)
  10 any later version.
  11
  12 GNU Classpath is distributed in the hope that it will be useful, but
  13 WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Classpath; see the file COPYING.  If not, write to the
  19 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301 USA.
  21
  22 Linking this library statically or dynamically with other modules is
  23 making a combined work based on this library.  Thus, the terms and
  24 conditions of the GNU General Public License cover the whole
  25 combination.
  26
  27 As a special exception, the copyright holders of this library give you
  28 permission to link this library with independent modules to produce an
  29 executable, regardless of the license terms of these independent
  30 modules, and to copy and distribute the resulting executable under
  31 terms of your choice, provided that you also meet, for each linked
  32 independent module, the terms and conditions of the license of that
  33 module.  An independent module is a module which is not derived from
  34 or based on this library.  If you modify this library, you may extend
  35 this exception to your version of the library, but you are not
  36 obligated to do so.  If you do not wish to do so, delete this
  37 exception statement from your version. */
  38
  39 package java.io;
  40
  41 import gnu.java.lang.CPStringBuilder;
  42
  43 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
  44  * "The Java Language Specification", ISBN 0-201-63451-1
  45  * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
  46  * Status:  Believed complete and correct.
  47  */
  48
  49 /**
  50  * This subclass of <code>FilteredInputStream</code> implements the
  51  * <code>DataInput</code> interface that provides method for reading primitive
  52  * Java data types from a stream.
  53  *
  54  * @see DataInput
  55  *
  56  * @author Warren Levy (warrenl@cygnus.com)
  57  * @author Aaron M. Renn (arenn@urbanophile.com)
  58  * @date October 20, 1998.
  59  */
  60 public class DataInputStream extends FilterInputStream implements DataInput
  61 {
  62   // Byte buffer, used to make primitive read calls more efficient.
  63   byte[] buf = new byte [8];
  64
  65   /**
  66    * This constructor initializes a new <code>DataInputStream</code>
  67    * to read from the specified subordinate stream.
  68    *
  69    * @param in The subordinate <code>InputStream</code> to read from
  70    */
  71   public DataInputStream (InputStream in)
  72   {
  73     super (in);
  74   }
  75
  76   /**
  77    * This method reads bytes from the underlying stream into the specified
  78    * byte array buffer.  It will attempt to fill the buffer completely, but
  79    * may return a short count if there is insufficient data remaining to be
  80    * read to fill the buffer.
  81    *
  82    * @param b The buffer into which bytes will be read.
  83    *
  84    * @return The actual number of bytes read, or -1 if end of stream reached
  85    * before reading any bytes.
  86    *
  87    * @exception IOException If an error occurs.
  88    */
  89   public final int read (byte[] b) throws IOException
  90   {
  91     return in.read (b, 0, b.length);
  92   }
  93
  94   /**
  95    * This method reads bytes from the underlying stream into the specified
  96    * byte array buffer.  It will attempt to read <code>len</code> bytes and
  97    * will start storing them at position <code>off</code> into the buffer.
  98    * This method can return a short count if there is insufficient data
  99    * remaining to be read to complete the desired read length.
 100    *
 101    * @param b The buffer into which bytes will be read.
 102    * @param off The offset into the buffer to start storing bytes.
 103    * @param len The requested number of bytes to read.
 104    *
 105    * @return The actual number of bytes read, or -1 if end of stream reached
 106    * before reading any bytes.
 107    *
 108    * @exception IOException If an error occurs.
 109    */
 110   public final int read (byte[] b, int off, int len) throws IOException
 111   {
 112     return in.read (b, off, len);
 113   }
 114
 115   /**
 116    * This method reads a Java boolean value from an input stream.  It does
 117    * so by reading a single byte of data.  If that byte is zero, then the
 118    * value returned is <code>false</code>.  If the byte is non-zero, then
 119    * the value returned is <code>true</code>.
 120    * <p>
 121    * This method can read a <code>boolean</code> written by an object
 122    * implementing the <code>writeBoolean()</code> method in the
 123    * <code>DataOutput</code> interface.
 124    *
 125    * @return The <code>boolean</code> value read
 126    *
 127    * @exception EOFException If end of file is reached before reading
 128    * the boolean
 129    * @exception IOException If any other error occurs
 130    *
 131    * @see DataOutput#writeBoolean
 132    */
 133   public final boolean readBoolean () throws IOException
 134   {
 135     return convertToBoolean (in.read ());
 136   }
 137
 138   /**
 139    * This method reads a Java byte value from an input stream.  The value
 140    * is in the range of -128 to 127.
 141    * <p>
 142    * This method can read a <code>byte</code> written by an object
 143    * implementing the <code>writeByte()</code> method in the
 144    * <code>DataOutput</code> interface.
 145    *
 146    * @return The <code>byte</code> value read
 147    *
 148    * @exception EOFException If end of file is reached before reading the byte
 149    * @exception IOException If any other error occurs
 150    *
 151    * @see DataOutput#writeByte
 152    */
 153   public final byte readByte () throws IOException
 154   {
 155     return convertToByte (in.read ());
 156   }
 157
 158   /**
 159    * This method reads a Java <code>char</code> value from an input stream.
 160    * It operates by reading two bytes from the stream and converting them to
 161    * a single 16-bit Java <code>char</code>.  The two bytes are stored most
 162    * significant byte first (i.e., "big endian") regardless of the native
 163    * host byte ordering.
 164    * <p>
 165    * As an example, if <code>byte1</code> and <code>byte2</code>
 166    * represent the first and second byte read from the stream
 167    * respectively, they will be transformed to a <code>char</code> in
 168    * the following manner:
 169    * <p>
 170    * <code>(char)(((byte1 &amp; 0xFF) &lt;&lt; 8) | (byte2 &amp; 0xFF)</code>
 171    * <p>
 172    * This method can read a <code>char</code> written by an object
 173    * implementing the <code>writeChar()</code> method in the
 174    * <code>DataOutput</code> interface.
 175    *
 176    * @return The <code>char</code> value read
 177    *
 178    * @exception EOFException If end of file is reached before reading the char
 179    * @exception IOException If any other error occurs
 180    *
 181    * @see DataOutput#writeChar
 182    */
 183   public final char readChar () throws IOException
 184   {
 185     readFully (buf, 0, 2);
 186     return convertToChar (buf);
 187   }
 188
 189   /**
 190    * This method reads a Java double value from an input stream.  It operates
 191    * by first reading a <code>long</code> value from the stream by calling the
 192    * <code>readLong()</code> method in this interface, then converts
 193    * that <code>long</code> to a <code>double</code> using the
 194    * <code>longBitsToDouble</code> method in the class
 195    * <code>java.lang.Double</code>
 196    * <p>
 197    * This method can read a <code>double</code> written by an object
 198    * implementing the <code>writeDouble()</code> method in the
 199    * <code>DataOutput</code> interface.
 200    *
 201    * @return The <code>double</code> value read
 202    *
 203    * @exception EOFException If end of file is reached before reading
 204    * the double
 205    * @exception IOException If any other error occurs
 206    *
 207    * @see DataOutput#writeDouble
 208    * @see java.lang.Double#longBitsToDouble
 209    */
 210   public final double readDouble () throws IOException
 211   {
 212     return Double.longBitsToDouble (readLong ());
 213   }
 214
 215   /**
 216    * This method reads a Java float value from an input stream.  It
 217    * operates by first reading an <code>int</code> value from the
 218    * stream by calling the <code>readInt()</code> method in this
 219    * interface, then converts that <code>int</code> to a
 220    * <code>float</code> using the <code>intBitsToFloat</code> method
 221    * in the class <code>java.lang.Float</code>
 222    * <p>
 223    * This method can read a <code>float</code> written by an object
 224    * implementing the <code>writeFloat()</code> method in the
 225    * <code>DataOutput</code> interface.
 226    *
 227    * @return The <code>float</code> value read
 228    *
 229    * @exception EOFException If end of file is reached before reading the float
 230    * @exception IOException If any other error occurs
 231    *
 232    * @see DataOutput#writeFloat
 233    * @see java.lang.Float#intBitsToFloat
 234    */
 235   public final float readFloat () throws IOException
 236   {
 237     return Float.intBitsToFloat (readInt ());
 238   }
 239
 240   /**
 241    * This method reads raw bytes into the passed array until the array is
 242    * full.  Note that this method blocks until the data is available and
 243    * throws an exception if there is not enough data left in the stream to
 244    * fill the buffer.  Note also that zero length buffers are permitted.
 245    * In this case, the method will return immediately without reading any
 246    * bytes from the stream.
 247    *
 248    * @param b The buffer into which to read the data
 249    *
 250    * @exception EOFException If end of file is reached before filling the
 251    * buffer
 252    * @exception IOException If any other error occurs
 253    */
 254   public final void readFully (byte[] b) throws IOException
 255   {
 256     readFully (b, 0, b.length);
 257   }
 258
 259   /**
 260    * This method reads raw bytes into the passed array <code>buf</code>
 261    * starting
 262    * <code>offset</code> bytes into the buffer.  The number of bytes read
 263    * will be
 264    * exactly <code>len</code>.  Note that this method blocks until the data is
 265    * available and throws an exception if there is not enough data left in
 266    * the stream to read <code>len</code> bytes.  Note also that zero length
 267    * buffers are permitted.  In this case, the method will return immediately
 268    * without reading any bytes from the stream.
 269    *
 270    * @param buf The buffer into which to read the data
 271    * @param offset The offset into the buffer to start storing data
 272    * @param len The number of bytes to read into the buffer
 273    *
 274    * @exception EOFException If end of file is reached before filling the
 275    * buffer
 276    * @exception IOException If any other error occurs
 277    */
 278   public final void readFully (byte[] buf, int offset, int len) throws IOException
 279   {
 280     if (len < 0)
 281       throw new IndexOutOfBoundsException("Negative length: " + len);
 282
 283     while (len > 0)
 284       {
 285         // in.read will block until some data is available.
 286         int numread = in.read (buf, offset, len);
 287         if (numread < 0)
 288           throw new EOFException ();
 289         len -= numread;
 290         offset += numread;
 291       }
 292   }
 293
 294   /**
 295    * This method reads a Java <code>int</code> value from an input stream
 296    * It operates by reading four bytes from the stream and converting them to
 297    * a single Java <code>int</code>.  The bytes are stored most
 298    * significant byte first (i.e., "big endian") regardless of the native
 299    * host byte ordering.
 300    * <p>
 301    * As an example, if <code>byte1</code> through <code>byte4</code> represent
 302    * the first four bytes read from the stream, they will be
 303    * transformed to an <code>int</code> in the following manner:
 304    * <p>
 305    * <code>(int)(((byte1 &amp; 0xFF) &lt;&lt; 24) + ((byte2 &amp; 0xFF) &lt;&lt; 16) +
 306    * ((byte3 &amp; 0xFF)&lt;&lt; 8) + (byte4 &amp; 0xFF)))</code>
 307    * <p>
 308    * The value returned is in the range of -2147483648 to 2147483647.
 309    * <p>
 310    * This method can read an <code>int</code> written by an object
 311    * implementing the <code>writeInt()</code> method in the
 312    * <code>DataOutput</code> interface.
 313    *
 314    * @return The <code>int</code> value read
 315    *
 316    * @exception EOFException If end of file is reached before reading the int
 317    * @exception IOException If any other error occurs
 318    *
 319    * @see DataOutput#writeInt
 320    */
 321   public final int readInt () throws IOException
 322   {
 323     readFully (buf, 0, 4);
 324     return convertToInt (buf);
 325   }
 326
 327   /**
 328    * This method reads the next line of text data from an input
 329    * stream.  It operates by reading bytes and converting those bytes
 330    * to <code>char</code> values by treating the byte read as the low
 331    * eight bits of the <code>char</code> and using 0 as the high eight
 332    * bits.  Because of this, it does not support the full 16-bit
 333    * Unicode character set.
 334    * <p>
 335    * The reading of bytes ends when either the end of file or a line
 336    * terminator is encountered.  The bytes read are then returned as a
 337    * <code>String</code> A line terminator is a byte sequence
 338    * consisting of either <code>\r</code>, <code>\n</code> or
 339    * <code>\r\n</code>.  These termination charaters are discarded and
 340    * are not returned as part of the string.
 341    * <p>
 342    * This method can read data that was written by an object implementing the
 343    * <code>writeLine()</code> method in <code>DataOutput</code>.
 344    *
 345    * @return The line read as a <code>String</code>
 346    *
 347    * @exception IOException If an error occurs
 348    *
 349    * @see DataOutput
 350    *
 351    * @deprecated
 352    */
 353   public final String readLine() throws IOException
 354   {
 355     CPStringBuilder strb = new CPStringBuilder();
 356
 357     while (true)
 358       {
 359         int c = in.read();
 360         if (c == -1)    // got an EOF
 361             return strb.length() > 0 ? strb.toString() : null;
 362         if (c == '\r')
 363           {
 364             int next_c = in.read();
 365             if (next_c != '\n' && next_c != -1)
 366               {
 367                 if (!(in instanceof PushbackInputStream))
 368                   in = new PushbackInputStream(in);
 369                 ((PushbackInputStream) in).unread(next_c);
 370               }
 371             break;
 372           }
 373         if (c == '\n')
 374             break;
 375         strb.append((char) c);
 376       }
 377
 378     return strb.length() > 0 ? strb.toString() : "";
 379   }
 380
 381   /**
 382    * This method reads a Java <code>long</code> value from an input stream
 383    * It operates by reading eight bytes from the stream and converting them to
 384    * a single Java <code>long</code>.  The bytes are stored most
 385    * significant byte first (i.e., "big endian") regardless of the native
 386    * host byte ordering.
 387    * <p>
 388    * As an example, if <code>byte1</code> through <code>byte8</code> represent
 389    * the first eight bytes read from the stream, they will be
 390    * transformed to an <code>long</code> in the following manner:
 391    * <p>
 392    * <code>(long)(((byte1 &amp; 0xFF) &lt;&lt; 56) + ((byte2 &amp; 0xFF) &lt;&lt; 48) +
 393    * ((byte3 &amp; 0xFF) &lt;&lt; 40) + ((byte4 &amp; 0xFF) &lt;&lt; 32) +
 394    * ((byte5 &amp; 0xFF) &lt;&lt; 24) + ((byte6 &amp; 0xFF) &lt;&lt; 16) +
 395    * ((byte7 &amp; 0xFF) &lt;&lt; 8) + (byte8 &amp; 0xFF)))
 396    * </code>
 397    * <p>
 398    * The value returned is in the range of -9223372036854775808 to
 399    * 9223372036854775807.
 400    * <p>
 401    * This method can read an <code>long</code> written by an object
 402    * implementing the <code>writeLong()</code> method in the
 403    * <code>DataOutput</code> interface.
 404    *
 405    * @return The <code>long</code> value read
 406    *
 407    * @exception EOFException If end of file is reached before reading the long
 408    * @exception IOException If any other error occurs
 409    *
 410    * @see DataOutput#writeLong
 411    */
 412   public final long readLong () throws IOException
 413   {
 414     readFully (buf, 0, 8);
 415     return convertToLong (buf);
 416   }
 417
 418   /**
 419    * This method reads a signed 16-bit value into a Java in from the
 420    * stream.  It operates by reading two bytes from the stream and
 421    * converting them to a single 16-bit Java <code>short</code>.  The
 422    * two bytes are stored most significant byte first (i.e., "big
 423    * endian") regardless of the native host byte ordering.
 424    * <p>
 425    * As an example, if <code>byte1</code> and <code>byte2</code>
 426    * represent the first and second byte read from the stream
 427    * respectively, they will be transformed to a <code>short</code>. in
 428    * the following manner:
 429    * <p>
 430    * <code>(short)(((byte1 &amp; 0xFF) &lt;&lt; 8) | (byte2 &amp; 0xFF))</code>
 431    * <p>
 432    * The value returned is in the range of -32768 to 32767.
 433    * <p>
 434    * This method can read a <code>short</code> written by an object
 435    * implementing the <code>writeShort()</code> method in the
 436    * <code>DataOutput</code> interface.
 437    *
 438    * @return The <code>short</code> value read
 439    *
 440    * @exception EOFException If end of file is reached before reading the value
 441    * @exception IOException If any other error occurs
 442    *
 443    * @see DataOutput#writeShort
 444    */
 445   public final short readShort () throws IOException
 446   {
 447     readFully (buf, 0, 2);
 448     return convertToShort (buf);
 449   }
 450
 451   /**
 452    * This method reads 8 unsigned bits into a Java <code>int</code>
 453    * value from the stream. The value returned is in the range of 0 to
 454    * 255.
 455    * <p>
 456    * This method can read an unsigned byte written by an object
 457    * implementing the <code>writeUnsignedByte()</code> method in the
 458    * <code>DataOutput</code> interface.
 459    *
 460    * @return The unsigned bytes value read as a Java <code>int</code>.
 461    *
 462    * @exception EOFException If end of file is reached before reading the value
 463    * @exception IOException If any other error occurs
 464    *
 465    * @see DataOutput#writeByte
 466    */
 467   public final int readUnsignedByte () throws IOException
 468   {
 469     return convertToUnsignedByte (in.read ());
 470   }
 471
 472   /**
 473    * This method reads 16 unsigned bits into a Java int value from the stream.
 474    * It operates by reading two bytes from the stream and converting them to
 475    * a single Java <code>int</code>  The two bytes are stored most
 476    * significant byte first (i.e., "big endian") regardless of the native
 477    * host byte ordering.
 478    * <p>
 479    * As an example, if <code>byte1</code> and <code>byte2</code>
 480    * represent the first and second byte read from the stream
 481    * respectively, they will be transformed to an <code>int</code> in
 482    * the following manner:
 483    * <p>
 484    * <code>(int)(((byte1 &amp; 0xFF) &lt;&lt; 8) + (byte2 &amp; 0xFF))</code>
 485    * <p>
 486    * The value returned is in the range of 0 to 65535.
 487    * <p>
 488    * This method can read an unsigned short written by an object
 489    * implementing the <code>writeUnsignedShort()</code> method in the
 490    * <code>DataOutput</code> interface.
 491    *
 492    * @return The unsigned short value read as a Java <code>int</code>
 493    *
 494    * @exception EOFException If end of file is reached before reading the value
 495    * @exception IOException If any other error occurs
 496    *
 497    * @see DataOutput#writeShort
 498    */
 499   public final int readUnsignedShort () throws IOException
 500   {
 501     readFully (buf, 0, 2);
 502     return convertToUnsignedShort (buf);
 503   }
 504
 505   /**
 506    * This method reads a <code>String</code> from an input stream that
 507    * is encoded in a modified UTF-8 format.  This format has a leading
 508    * two byte sequence that contains the remaining number of bytes to
 509    * read.  This two byte sequence is read using the
 510    * <code>readUnsignedShort()</code> method of this interface.
 511    * <p>
 512    * After the number of remaining bytes have been determined, these
 513    * bytes are read an transformed into <code>char</code> values.
 514    * These <code>char</code> values are encoded in the stream using
 515    * either a one, two, or three byte format.  The particular format
 516    * in use can be determined by examining the first byte read.
 517    * <p>
 518    * If the first byte has a high order bit of 0, then that character
 519    * consists on only one byte.  This character value consists of
 520    * seven bits that are at positions 0 through 6 of the byte.  As an
 521    * example, if <code>byte1</code> is the byte read from the stream,
 522    * it would be converted to a <code>char</code> like so:
 523    * <p>
 524    * <code>(char)byte1</code>
 525    * <p>
 526    * If the first byte has 110 as its high order bits, then the
 527    * character consists of two bytes.  The bits that make up the character
 528    * value are in positions 0 through 4 of the first byte and bit positions
 529    * 0 through 5 of the second byte.  (The second byte should have
 530    * 10 as its high order bits).  These values are in most significant
 531    * byte first (i.e., "big endian") order.
 532    * <p>
 533    * As an example, if <code>byte1</code> and <code>byte2</code> are
 534    * the first two bytes read respectively, and the high order bits of
 535    * them match the patterns which indicate a two byte character
 536    * encoding, then they would be converted to a Java
 537    * <code>char</code> like so:
 538    * <p>
 539    * <code>(char)(((byte1 & 0x1F) << 6) | (byte2 & 0x3F))</code>
 540    * <p>
 541    * If the first byte has a 1110 as its high order bits, then the
 542    * character consists of three bytes.  The bits that make up the character
 543    * value are in positions 0 through 3 of the first byte and bit positions
 544    * 0 through 5 of the other two bytes.  (The second and third bytes should
 545    * have 10 as their high order bits).  These values are in most
 546    * significant byte first (i.e., "big endian") order.
 547    * <p>
 548    * As an example, if <code>byte1</code> <code>byte2</code> and
 549    * <code>byte3</code> are the three bytes read, and the high order
 550    * bits of them match the patterns which indicate a three byte
 551    * character encoding, then they would be converted to a Java
 552    * <code>char</code> like so:
 553    * <p>
 554    * <code>(char)(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) |
 555    * (byte3 & 0x3F))</code>
 556    * <p>
 557    * Note that all characters are encoded in the method that requires
 558    * the fewest number of bytes with the exception of the character
 559    * with the value of <code>&#92;u0000</code> which is encoded as two
 560    * bytes.  This is a modification of the UTF standard used to
 561    * prevent C language style <code>NUL</code> values from appearing
 562    * in the byte stream.
 563    * <p>
 564    * This method can read data that was written by an object implementing the
 565    * <code>writeUTF()</code> method in <code>DataOutput</code>
 566    *
 567    * @return The <code>String</code> read
 568    *
 569    * @exception EOFException If end of file is reached before reading
 570    * the String
 571    * @exception UTFDataFormatException If the data is not in UTF-8 format
 572    * @exception IOException If any other error occurs
 573    *
 574    * @see DataOutput#writeUTF
 575    */
 576   public final String readUTF () throws IOException
 577   {
 578     return readUTF (this);
 579   }
 580
 581   /**
 582    * This method reads a String encoded in UTF-8 format from the
 583    * specified <code>DataInput</code> source.
 584    *
 585    * @param in The <code>DataInput</code> source to read from
 586    *
 587    * @return The String read from the source
 588    *
 589    * @exception IOException If an error occurs
 590    *
 591    * @see DataInput#readUTF
 592    */
 593   public static final String readUTF(DataInput in) throws IOException
 594   {
 595     final int UTFlen = in.readUnsignedShort ();
 596
 597     return readUTF(in, UTFlen);
 598   }
 599
 600   /**
 601    * This method is similar to <code>readUTF</code>, but the
 602    * UTF-8 byte length is in 64 bits.
 603    * This method is not public. It is used by <code>ObjectInputStream</code>.
 604    *
 605    * @return The <code>String</code> read
 606    *
 607    * @exception EOFException If end of file is reached before reading
 608    * the String
 609    * @exception UTFDataFormatException If the data is not in UTF-8 format
 610    * @exception IOException If any other error occurs
 611    *
 612    * @see DataOutput#writeUTFLong
 613    */
 614   final String readUTFLong () throws IOException
 615   {
 616     long l = readLong ();
 617     if (l > Integer.MAX_VALUE)
 618       throw new IOException("The string length > Integer.MAX_VALUE");
 619     final int UTFlen = (int)l;
 620     return readUTF (this, UTFlen);
 621   }
 622
 623   /**
 624    * This method performs the main task of <code>readUTF</code> and
 625    * <code>readUTFLong</code>.
 626    *
 627    * @param in The <code>DataInput</code> source to read from
 628    *
 629    * @param len The UTF-8 byte length of the String to be read
 630    *
 631    * @return The String read from the source
 632    *
 633    * @exception IOException If an error occurs
 634    *
 635    * @see DataInput#readUTF
 636    */
 637   private static final String readUTF(DataInput in, int len) throws IOException
 638   {
 639     byte[] buf = new byte [len];
 640
 641     // This blocks until the entire string is available rather than
 642     // doing partial processing on the bytes that are available and then
 643     // blocking.  An advantage of the latter is that Exceptions
 644     // could be thrown earlier.  The former is a bit cleaner.
 645     in.readFully (buf, 0, len);
 646
 647     return convertFromUTF (buf);
 648   }
 649
 650   /**
 651    * This method attempts to skip and discard the specified number of bytes
 652    * in the input stream.  It may actually skip fewer bytes than requested.
 653    * This method will not skip any bytes if passed a negative number of bytes
 654    * to skip.
 655    *
 656    * @param n The requested number of bytes to skip.
 657    *
 658    * @return The requested number of bytes to skip.
 659    *
 660    * @exception IOException If an error occurs.
 661    * @specnote The JDK docs claim that this returns the number of bytes
 662    *  actually skipped. The JCL claims that this method can throw an
 663    *  EOFException. Neither of these appear to be true in the JDK 1.3's
 664    *  implementation. This tries to implement the actual JDK behaviour.
 665    */
 666   public final int skipBytes (int n) throws IOException
 667   {
 668     if (n <= 0)
 669       return 0;
 670     try
 671       {
 672         return (int) in.skip (n);
 673       }
 674     catch (EOFException x)
 675       {
 676         // do nothing.
 677       }
 678     return n;
 679   }
 680
 681   static boolean convertToBoolean (int b) throws EOFException
 682   {
 683     if (b < 0)
 684       throw new EOFException ();
 685
 686     return (b != 0);
 687   }
 688
 689   static byte convertToByte (int i) throws EOFException
 690   {
 691     if (i < 0)
 692       throw new EOFException ();
 693
 694     return (byte) i;
 695   }
 696
 697   static int convertToUnsignedByte (int i) throws EOFException
 698   {
 699     if (i < 0)
 700       throw new EOFException ();
 701
 702     return (i & 0xFF);
 703   }
 704
 705   static char convertToChar (byte[] buf)
 706   {
 707     return (char) ((buf [0] << 8)
 708                     | (buf [1] & 0xff));
 709   }
 710
 711   static short convertToShort (byte[] buf)
 712   {
 713     return (short) ((buf [0] << 8)
 714                     | (buf [1] & 0xff));
 715   }
 716
 717   static int convertToUnsignedShort (byte[] buf)
 718   {
 719     return (((buf [0] & 0xff) << 8)
 720             | (buf [1] & 0xff));
 721   }
 722
 723   static int convertToInt (byte[] buf)
 724   {
 725     return (((buf [0] & 0xff) << 24)
 726             | ((buf [1] & 0xff) << 16)
 727             | ((buf [2] & 0xff) << 8)
 728             | (buf [3] & 0xff));
 729   }
 730
 731   static long convertToLong (byte[] buf)
 732   {
 733     return (((long)(buf [0] & 0xff) << 56) |
 734             ((long)(buf [1] & 0xff) << 48) |
 735             ((long)(buf [2] & 0xff) << 40) |
 736             ((long)(buf [3] & 0xff) << 32) |
 737             ((long)(buf [4] & 0xff) << 24) |
 738             ((long)(buf [5] & 0xff) << 16) |
 739             ((long)(buf [6] & 0xff) <<  8) |
 740             ((long)(buf [7] & 0xff)));
 741   }
 742
 743   // FIXME: This method should be re-thought.  I suspect we have multiple
 744   // UTF-8 decoders floating around.  We should use the standard charset
 745   // converters, maybe and adding a direct call into one of the new
 746   // NIO converters for a super-fast UTF8 decode.
 747   static String convertFromUTF (byte[] buf)
 748     throws EOFException, UTFDataFormatException
 749   {
 750     // Give StringBuffer an initial estimated size to avoid
 751     // enlarge buffer frequently
 752     CPStringBuilder strbuf = new CPStringBuilder (buf.length / 2 + 2);
 753
 754     for (int i = 0; i < buf.length; )
 755       {
 756         if ((buf [i] & 0x80) == 0)              // bit pattern 0xxxxxxx
 757           strbuf.append ((char) (buf [i++] & 0xFF));
 758         else if ((buf [i] & 0xE0) == 0xC0)      // bit pattern 110xxxxx
 759           {
 760             if (i + 1 >= buf.length
 761                 || (buf [i + 1] & 0xC0) != 0x80)
 762               throw new UTFDataFormatException ();
 763
 764             strbuf.append((char) (((buf [i++] & 0x1F) << 6)
 765                                   | (buf [i++] & 0x3F)));
 766           }
 767         else if ((buf [i] & 0xF0) == 0xE0)      // bit pattern 1110xxxx
 768           {
 769             if (i + 2 >= buf.length
 770                 || (buf [i + 1] & 0xC0) != 0x80
 771                 || (buf [i + 2] & 0xC0) != 0x80)
 772               throw new UTFDataFormatException ();
 773
 774             strbuf.append ((char) (((buf [i++] & 0x0F) << 12)
 775                                    | ((buf [i++] & 0x3F) << 6)
 776                                    | (buf [i++] & 0x3F)));
 777           }
 778         else // must be ((buf [i] & 0xF0) == 0xF0 || (buf [i] & 0xC0) == 0x80)
 779           throw new UTFDataFormatException ();  // bit patterns 1111xxxx or
 780                                                 //              10xxxxxx
 781       }
 782
 783     return strbuf.toString ();
 784   }
 785 }