/*
 
* 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
     
java.io.DataInputStream
 
* @see
     
java.io.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.
     
*
     
* @paramb
   
the buffer into which the data is read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @paramb
   
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
  
EOFExceptionif 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.
     
* @returnthe 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}.
     
*
     
* @returnthe {@code boolean} value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe 8-bit value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe unsigned 8-bit value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe 16-bit value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe unsigned 16-bit value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe {@code char} value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe {@code int} value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe {@code long} value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe {@code float} value read.
     
* @exception
  
EOFExceptionif 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}.
     
*
     
* @returnthe {@code double} value read.
     
* @exception
  
EOFExceptionif 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
  
IOExceptionif 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.
     
* @returna Unicode string.
     
* @exception
  
EOFException
            
if this stream reaches the end
     
*
               
before reading all the bytes.
     
* @exception
  
IOException
             
if an I/O error occurs.
     
* @exception
  
UTFDataFormatExceptionif the bytes do not represent a
     
*
               
valid modified UTF-8 encoding of a string.
     
*/

    
String readUTF() throws IOException;
}