content: /*
   * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.io;
  
  /**
   * The {@code DataInput} interface provides
   * for reading bytes from a binary stream and
   * reconstructing from them data in any of
   * the Java primitive types. There is also
   * a
   * facility for reconstructing a {@code String}
   * from data in
   * <a href="#modified-utf-8">modified UTF-8</a>
   * format.
   * <p>
   * It is generally true of all the reading
   * routines in this interface that if end of
   * file is reached before the desired number
   * of bytes has been read, an {@code EOFException}
   * (which is a kind of {@code IOException})
   * is thrown. If any byte cannot be read for
   * any reason other than end of file, an {@code IOException}
   * other than {@code EOFException} is
   * thrown. In particular, an {@code IOException}
   * may be thrown if the input stream has been
   * closed.
   *
   * <h3><a name="modified-utf-8">Modified UTF-8</a></h3>
   * <p>
   * Implementations of the DataInput and DataOutput interfaces represent
   * Unicode strings in a format that is a slight modification of UTF-8.
   * (For information regarding the standard UTF-8 format, see section
   * <i>3.9 Unicode Encoding Forms</i> of <i>The Unicode Standard, Version
   * 4.0</i>).
   * Note that in the following table, the most significant bit appears in the
   * far left-hand column.
   *
   * <blockquote>
   *   <table border="1" cellspacing="0" cellpadding="8"
   *          summary="Bit values and bytes">
   *     <tr>
   *       <th colspan="9"><span style="font-weight:normal">
   *         All characters in the range {@code '\u005Cu0001'} to
   *         {@code '\u005Cu007F'} are represented by a single byte:</span></th>
   *     </tr>
   *     <tr>
   *       <td></td>
   *       <th colspan="8" id="bit_a">Bit Values</th>
   *     </tr>
   *     <tr>
   *       <th id="byte1_a">Byte 1</th>
   *       <td><center>0</center>
   *       <td colspan="7"><center>bits 6-0</center>
   *     </tr>
   *     <tr>
   *       <th colspan="9"><span style="font-weight:normal">
   *         The null character {@code '\u005Cu0000'} and characters
   *         in the range {@code '\u005Cu0080'} to {@code '\u005Cu07FF'} are
   *         represented by a pair of bytes:</span></th>
   *     </tr>
   *     <tr>
   *       <td></td>
   *       <th colspan="8" id="bit_b">Bit Values</th>
   *     </tr>
   *     <tr>
   *       <th id="byte1_b">Byte 1</th>
   *       <td><center>1</center>
   *       <td><center>1</center>
   *       <td><center>0</center>
   *       <td colspan="5"><center>bits 10-6</center>
   *     </tr>
   *     <tr>
   *       <th id="byte2_a">Byte 2</th>
   *       <td><center>1</center>
   *       <td><center>0</center>
   *       <td colspan="6"><center>bits 5-0</center>
   *     </tr>
   *     <tr>
   *       <th colspan="9"><span style="font-weight:normal">
   *         {@code char} values in the range {@code '\u005Cu0800'}
   *         to {@code '\u005CuFFFF'} are represented by three bytes:</span></th>
   *     </tr>
   *     <tr>
   *       <td></td>
   *       <th colspan="8"id="bit_c">Bit Values</th>
   *     </tr>
   *     <tr>
   *       <th id="byte1_c">Byte 1</th>
   *       <td><center>1</center>
   *       <td><center>1</center>
   *       <td><center>1</center>
   *       <td><center>0</center>
   *       <td colspan="4"><center>bits 15-12</center>
   *     </tr>
   *     <tr>
   *       <th id="byte2_b">Byte 2</th>
   *       <td><center>1</center>
   *       <td><center>0</center>
   *       <td colspan="6"><center>bits 11-6</center>
   *     </tr>
   *     <tr>
   *       <th id="byte3">Byte 3</th>
   *       <td><center>1</center>
   *       <td><center>0</center>
   *       <td colspan="6"><center>bits 5-0</center>
   *     </tr>
   *   </table>
   * </blockquote>
   * <p>
   * The differences between this format and the
   * standard UTF-8 format are the following:
   * <ul>
   * <li>The null byte {@code '\u005Cu0000'} is encoded in 2-byte format
   *     rather than 1-byte, so that the encoded strings never have
   *     embedded nulls.
   * <li>Only the 1-byte, 2-byte, and 3-byte formats are used.
   * <li><a href="../lang/Character.html#unicode">Supplementary characters</a>
   *     are represented in the form of surrogate pairs.
   * </ul>
   * @author  Frank Yellin
   * @see     DataInputStream
   * @see     DataOutput
   * @since   JDK1.0
   */
  public
  interface DataInput {
      /**
       * Reads some bytes from an input
       * stream and stores them into the buffer
       * array {@code b}. The number of bytes
       * read is equal
       * to the length of {@code b}.
       * <p>
       * This method blocks until one of the
       * following conditions occurs:
       * <ul>
       * <li>{@code b.length}
       * bytes of input data are available, in which
       * case a normal return is made.
       *
       * <li>End of
       * file is detected, in which case an {@code EOFException}
       * is thrown.
       *
       * <li>An I/O error occurs, in
       * which case an {@code IOException} other
       * than {@code EOFException} is thrown.
       * </ul>
       * <p>
       * If {@code b} is {@code null},
       * a {@code NullPointerException} is thrown.
       * If {@code b.length} is zero, then
       * no bytes are read. Otherwise, the first
       * byte read is stored into element {@code b[0]},
       * the next one into {@code b[1]}, and
       * so on.
       * If an exception is thrown from
       * this method, then it may be that some but
       * not all bytes of {@code b} have been
       * updated with data from the input stream.
       *
       * @param     b   the buffer into which the data is read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      void readFully(byte b[]) throws IOException;
  
      /**
       *
       * Reads {@code len}
       * bytes from
       * an input stream.
       * <p>
       * This method
       * blocks until one of the following conditions
       * occurs:
       * <ul>
       * <li>{@code len} bytes
       * of input data are available, in which case
       * a normal return is made.
       *
       * <li>End of file
       * is detected, in which case an {@code EOFException}
       * is thrown.
       *
       * <li>An I/O error occurs, in
       * which case an {@code IOException} other
       * than {@code EOFException} is thrown.
       * </ul>
       * <p>
       * If {@code b} is {@code null},
       * a {@code NullPointerException} is thrown.
       * If {@code off} is negative, or {@code len}
       * is negative, or {@code off+len} is
       * greater than the length of the array {@code b},
       * then an {@code IndexOutOfBoundsException}
       * is thrown.
       * If {@code len} is zero,
       * then no bytes are read. Otherwise, the first
       * byte read is stored into element {@code b[off]},
       * the next one into {@code b[off+1]},
       * and so on. The number of bytes read is,
       * at most, equal to {@code len}.
       *
       * @param     b   the buffer into which the data is read.
       * @param off  an int specifying the offset into the data.
       * @param len  an int specifying the number of bytes to read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      void readFully(byte b[], int off, int len) throws IOException;
  
      /**
       * Makes an attempt to skip over
       * {@code n} bytes
       * of data from the input
       * stream, discarding the skipped bytes. However,
       * it may skip
       * over some smaller number of
       * bytes, possibly zero. This may result from
       * any of a
       * number of conditions; reaching
       * end of file before {@code n} bytes
       * have been skipped is
       * only one possibility.
       * This method never throws an {@code EOFException}.
       * The actual
       * number of bytes skipped is returned.
       *
       * @param      n   the number of bytes to be skipped.
       * @return     the number of bytes actually skipped.
       * @exception  IOException   if an I/O error occurs.
       */
      int skipBytes(int n) throws IOException;
  
      /**
       * Reads one input byte and returns
       * {@code true} if that byte is nonzero,
       * {@code false} if that byte is zero.
       * This method is suitable for reading
       * the byte written by the {@code writeBoolean}
       * method of interface {@code DataOutput}.
       *
       * @return     the {@code boolean} value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      boolean readBoolean() throws IOException;
  
      /**
       * Reads and returns one input byte.
       * The byte is treated as a signed value in
       * the range {@code -128} through {@code 127},
       * inclusive.
       * This method is suitable for
       * reading the byte written by the {@code writeByte}
       * method of interface {@code DataOutput}.
       *
       * @return     the 8-bit value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      byte readByte() throws IOException;
  
      /**
       * Reads one input byte, zero-extends
       * it to type {@code int}, and returns
       * the result, which is therefore in the range
       * {@code 0}
       * through {@code 255}.
       * This method is suitable for reading
       * the byte written by the {@code writeByte}
       * method of interface {@code DataOutput}
       * if the argument to {@code writeByte}
       * was intended to be a value in the range
       * {@code 0} through {@code 255}.
       *
       * @return     the unsigned 8-bit value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      int readUnsignedByte() throws IOException;
  
      /**
       * Reads two input bytes and returns
       * a {@code short} value. Let {@code a}
       * be the first byte read and {@code b}
       * be the second byte. The value
       * returned
       * is:
       * <pre>{@code (short)((a << 8) | (b & 0xff))
       * }</pre>
       * This method
       * is suitable for reading the bytes written
       * by the {@code writeShort} method of
       * interface {@code DataOutput}.
       *
       * @return     the 16-bit value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      short readShort() throws IOException;
  
      /**
       * Reads two input bytes and returns
       * an {@code int} value in the range {@code 0}
       * through {@code 65535}. Let {@code a}
       * be the first byte read and
       * {@code b}
       * be the second byte. The value returned is:
       * <pre>{@code (((a & 0xff) << 8) | (b & 0xff))
       * }</pre>
       * This method is suitable for reading the bytes
       * written by the {@code writeShort} method
       * of interface {@code DataOutput}  if
       * the argument to {@code writeShort}
       * was intended to be a value in the range
       * {@code 0} through {@code 65535}.
       *
       * @return     the unsigned 16-bit value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      int readUnsignedShort() throws IOException;
  
      /**
       * Reads two input bytes and returns a {@code char} value.
       * Let {@code a}
       * be the first byte read and {@code b}
       * be the second byte. The value
       * returned is:
       * <pre>{@code (char)((a << 8) | (b & 0xff))
       * }</pre>
       * This method
       * is suitable for reading bytes written by
       * the {@code writeChar} method of interface
       * {@code DataOutput}.
       *
       * @return     the {@code char} value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      char readChar() throws IOException;
  
      /**
       * Reads four input bytes and returns an
       * {@code int} value. Let {@code a-d}
       * be the first through fourth bytes read. The value returned is:
       * <pre>{@code
       * (((a & 0xff) << 24) | ((b & 0xff) << 16) |
       *  ((c & 0xff) <<  8) | (d & 0xff))
       * }</pre>
       * This method is suitable
       * for reading bytes written by the {@code writeInt}
       * method of interface {@code DataOutput}.
       *
       * @return     the {@code int} value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      int readInt() throws IOException;
  
      /**
       * Reads eight input bytes and returns
       * a {@code long} value. Let {@code a-h}
       * be the first through eighth bytes read.
       * The value returned is:
       * <pre>{@code
       * (((long)(a & 0xff) << 56) |
       *  ((long)(b & 0xff) << 48) |
       *  ((long)(c & 0xff) << 40) |
       *  ((long)(d & 0xff) << 32) |
       *  ((long)(e & 0xff) << 24) |
       *  ((long)(f & 0xff) << 16) |
       *  ((long)(g & 0xff) <<  8) |
       *  ((long)(h & 0xff)))
       * }</pre>
       * <p>
       * This method is suitable
       * for reading bytes written by the {@code writeLong}
       * method of interface {@code DataOutput}.
       *
       * @return     the {@code long} value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      long readLong() throws IOException;
  
      /**
       * Reads four input bytes and returns
       * a {@code float} value. It does this
       * by first constructing an {@code int}
       * value in exactly the manner
       * of the {@code readInt}
       * method, then converting this {@code int}
       * value to a {@code float} in
       * exactly the manner of the method {@code Float.intBitsToFloat}.
       * This method is suitable for reading
       * bytes written by the {@code writeFloat}
       * method of interface {@code DataOutput}.
       *
       * @return     the {@code float} value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      float readFloat() throws IOException;
  
      /**
       * Reads eight input bytes and returns
       * a {@code double} value. It does this
       * by first constructing a {@code long}
       * value in exactly the manner
       * of the {@code readLong}
       * method, then converting this {@code long}
       * value to a {@code double} in exactly
       * the manner of the method {@code Double.longBitsToDouble}.
       * This method is suitable for reading
       * bytes written by the {@code writeDouble}
       * method of interface {@code DataOutput}.
       *
       * @return     the {@code double} value read.
       * @exception  EOFException  if this stream reaches the end before reading
       *               all the bytes.
       * @exception  IOException   if an I/O error occurs.
       */
      double readDouble() throws IOException;
  
      /**
       * Reads the next line of text from the input stream.
       * It reads successive bytes, converting
       * each byte separately into a character,
       * until it encounters a line terminator or
       * end of
       * file; the characters read are then
       * returned as a {@code String}. Note
       * that because this
       * method processes bytes,
       * it does not support input of the full Unicode
       * character set.
       * <p>
       * If end of file is encountered
       * before even one byte can be read, then {@code null}
       * is returned. Otherwise, each byte that is
       * read is converted to type {@code char}
       * by zero-extension. If the character {@code '\n'}
       * is encountered, it is discarded and reading
       * ceases. If the character {@code '\r'}
       * is encountered, it is discarded and, if
       * the following byte converts &#32;to the
       * character {@code '\n'}, then that is
       * discarded also; reading then ceases. If
       * end of file is encountered before either
       * of the characters {@code '\n'} and
       * {@code '\r'} is encountered, reading
       * ceases. Once reading has ceased, a {@code String}
       * is returned that contains all the characters
       * read and not discarded, taken in order.
       * Note that every character in this string
       * will have a value less than {@code \u005Cu0100},
       * that is, {@code (char)256}.
       *
       * @return the next line of text from the input stream,
       *         or {@code null} if the end of file is
       *         encountered before a byte can be read.
       * @exception  IOException  if an I/O error occurs.
       */
      String readLine() throws IOException;
  
      /**
       * Reads in a string that has been encoded using a
       * <a href="#modified-utf-8">modified UTF-8</a>
       * format.
       * The general contract of {@code readUTF}
       * is that it reads a representation of a Unicode
       * character string encoded in modified
       * UTF-8 format; this string of characters
       * is then returned as a {@code String}.
       * <p>
       * First, two bytes are read and used to
       * construct an unsigned 16-bit integer in
       * exactly the manner of the {@code readUnsignedShort}
       * method . This integer value is called the
       * <i>UTF length</i> and specifies the number
       * of additional bytes to be read. These bytes
       * are then converted to characters by considering
       * them in groups. The length of each group
       * is computed from the value of the first
       * byte of the group. The byte following a
       * group, if any, is the first byte of the
       * next group.
       * <p>
       * If the first byte of a group
       * matches the bit pattern {@code 0xxxxxxx}
       * (where {@code x} means "may be {@code 0}
       * or {@code 1}"), then the group consists
       * of just that byte. The byte is zero-extended
       * to form a character.
       * <p>
       * If the first byte
       * of a group matches the bit pattern {@code 110xxxxx},
       * then the group consists of that byte {@code a}
       * and a second byte {@code b}. If there
       * is no byte {@code b} (because byte
       * {@code a} was the last of the bytes
       * to be read), or if byte {@code b} does
       * not match the bit pattern {@code 10xxxxxx},
       * then a {@code UTFDataFormatException}
       * is thrown. Otherwise, the group is converted
       * to the character:
       * <pre>{@code (char)(((a & 0x1F) << 6) | (b & 0x3F))
       * }</pre>
       * If the first byte of a group
       * matches the bit pattern {@code 1110xxxx},
       * then the group consists of that byte {@code a}
       * and two more bytes {@code b} and {@code c}.
       * If there is no byte {@code c} (because
       * byte {@code a} was one of the last
       * two of the bytes to be read), or either
       * byte {@code b} or byte {@code c}
       * does not match the bit pattern {@code 10xxxxxx},
       * then a {@code UTFDataFormatException}
       * is thrown. Otherwise, the group is converted
       * to the character:
       * <pre>{@code
       * (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))
       * }</pre>
       * If the first byte of a group matches the
       * pattern {@code 1111xxxx} or the pattern
       * {@code 10xxxxxx}, then a {@code UTFDataFormatException}
       * is thrown.
       * <p>
       * If end of file is encountered
       * at any time during this entire process,
       * then an {@code EOFException} is thrown.
       * <p>
       * After every group has been converted to
       * a character by this process, the characters
       * are gathered, in the same order in which
       * their corresponding groups were read from
       * the input stream, to form a {@code String},
       * which is returned.
       * <p>
       * The {@code writeUTF}
       * method of interface {@code DataOutput}
       * may be used to write data that is suitable
       * for reading by this method.
       * @return     a Unicode string.
       * @exception  EOFException            if this stream reaches the end
       *               before reading all the bytes.
       * @exception  IOException             if an I/O error occurs.
       * @exception  UTFDataFormatException  if the bytes do not represent a
       *               valid modified UTF-8 encoding of a string.
       */
      String readUTF() throws IOException;
  }
  