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 * 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

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 * accompanied this code).

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 * You should have received a copy of the GNU General Public License version

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 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

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.

 *

 * <h2><a id="modified-utf-8">Modified UTF-8</a></h2>

 * <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>)

 *

 * <ul>

 * <li>Characters in the range {@code '\u005Cu0001'} to

 *         {@code '\u005Cu007F'} are represented by a single byte.

 * <li>The null character {@code '\u005Cu0000'} and characters

 *         in the range {@code '\u005Cu0080'} to {@code '\u005Cu07FF'} are

 *         represented by a pair of bytes.

 * <li>Characters in the range {@code '\u005Cu0800'}

 *         to {@code '\u005CuFFFF'} are represented by three bytes.

 * </ul>

 *

 *   <table class="plain" style="margin-left:2em;">

 *     <caption>Encoding of UTF-8 values</caption>

 *     <thead>

 *     <tr>

 *       <th scope="col" rowspan="2">Value</th>

 *       <th scope="col" rowspan="2">Byte</th>

 *       <th scope="col" colspan="8" id="bit_a">Bit Values</th>

 *     </tr>

 *     <tr>

 *       <!-- Value -->

 *       <!-- Byte -->

 *       <th scope="col" style="width:3em"> 7 </th>

 *       <th scope="col" style="width:3em"> 6 </th>

 *       <th scope="col" style="width:3em"> 5 </th>

 *       <th scope="col" style="width:3em"> 4 </th>

 *       <th scope="col" style="width:3em"> 3 </th>

 *       <th scope="col" style="width:3em"> 2 </th>

 *       <th scope="col" style="width:3em"> 1 </th>

 *       <th scope="col" style="width:3em"> 0 </th>

 *     </thead>

 *     <tbody>

 *     <tr>

 *       <th scope="row" style="text-align:left; font-weight:normal">

 *         {@code \u005Cu0001} to {@code \u005Cu007F} </th>

 *       <th scope="row" style="font-weight:normal; text-align:center"> 1 </th>

 *       <td style="text-align:center">0

 *       <td colspan="7" style="text-align:right; padding-right:6em">bits 6-0

 *     </tr>

 *     <tr>

 *       <th scope="row" rowspan="2" style="text-align:left; font-weight:normal">

 *           {@code \u005Cu0000},<br>

 *           {@code \u005Cu0080} to {@code \u005Cu07FF} </th>

 *       <th scope="row" style="font-weight:normal; text-align:center"> 1 </th>

 *       <td style="text-align:center">1

 *       <td style="text-align:center">1

 *       <td style="text-align:center">0

 *       <td colspan="5" style="text-align:right; padding-right:6em">bits 10-6

 *     </tr>

 *     <tr>

 *       <!-- (value) -->

 *       <th scope="row" style="font-weight:normal; text-align:center"> 2 </th>

 *       <td style="text-align:center">1

 *       <td style="text-align:center">0

 *       <td colspan="6" style="text-align:right; padding-right:6em">bits 5-0

 *     </tr>

 *     <tr>

 *       <th scope="row" rowspan="3" style="text-align:left; font-weight:normal">

 *         {@code \u005Cu0800} to {@code \u005CuFFFF} </th>

 *       <th scope="row" style="font-weight:normal; text-align:center"> 1 </th>

 *       <td style="text-align:center">1

 *       <td style="text-align:center">1

 *       <td style="text-align:center">1

 *       <td style="text-align:center">0

 *       <td colspan="4" style="text-align:right; padding-right:6em">bits 15-12

 *     </tr>

 *     <tr>

 *       <!-- (value) -->

 *       <th scope="row" style="font-weight:normal; text-align:center"> 2 </th>

 *       <td style="text-align:center">1

 *       <td style="text-align:center">0

 *       <td colspan="6" style="text-align:right; padding-right:6em">bits 11-6

 *     </tr>

 *     <tr>

 *       <!-- (value) -->

 *       <th scope="row" style="font-weight:normal; text-align:center"> 3 </th>

 *       <td style="text-align:center">1

 *       <td style="text-align:center">0

 *       <td colspan="6" style="text-align:right; padding-right:6em">bits 5-0

 *     </tr>

 *     </tbody>

 *   </table>

 *

 * <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     java.io.DataInputStream

 * @see     java.io.DataOutput

 * @since   1.0

 */

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.

     * @throws  NullPointerException if {@code b} is {@code null}.

     * @throws  EOFException  if this stream reaches the end before reading

     *          all the bytes.

     * @throws  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 in the data array {@code b}.

     * @param   len  an int specifying the number of bytes to read.

     * @throws  NullPointerException if {@code b} is {@code null}.

     * @throws  IndexOutOfBoundsException if {@code off} is negative,

     *          {@code len} is negative, or {@code len} is greater than

     *          {@code b.length - off}.

     * @throws  EOFException  if this stream reaches the end before reading

     *          all the bytes.

     * @throws  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  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