/*
*
*
* Copyright 1990-2009 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program 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.
*
* This program 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 at /legal/license.txt).
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*/
package java.io;
/**
* The <code>DataInput</code> 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</code>
* from data in Java modified UTF-8 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</code>
* (which is a kind of <code>IOException</code>)
* is thrown. If any byte cannot be read for
* any reason other than end of file, an <code>IOException</code>
* other than <code>EOFException</code> is
* thrown. In particular, an <code>IOException</code>
* may be thrown if the input stream has been
* closed.
*
* @version 12/17/01 (CLDC 1.1)
* @see java.io.DataInputStream
* @see java.io.DataOutput
* @since JDK1.0, CLDC 1.0
*/
public
interface DataInput {
/**
* Reads some bytes from an input
* stream and stores them into the buffer
* array <code>b</code>. The number of bytes
* read is equal
* to the length of <code>b</code>.
* <p>
* This method blocks until one of the
* following conditions occurs:<p>
* <ul>
* <li><code>b.length</code>
* 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</code> is thrown.
*
* <li>An I/O error occurs, in which case an
* <code>IOException</code> other than
* <code>EOFException</code> is thrown.
* </ul>
* <p>
* If <code>b</code> is <code>null</code>,
* a <code>NullPointerException</code> is thrown.
* If <code>b.length</code> is zero, then
* no bytes are read. Otherwise, the first
* byte read is stored into element <code>b[0]</code>,
* the next one into <code>b[1]</code>, and
* so on.
* If an exception is thrown from
* this method, then it may be that some but
* not all bytes of <code>b</code> 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</code>
* bytes from
* an input stream.
* <p>
* This method
* blocks until one of the following conditions
* occurs:<p>
* <ul>
* <li><code>len</code> 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</code>
* is thrown.
*
* <li>An I/O error occurs, in
* which case an <code>IOException</code> other
* than <code>EOFException</code> is thrown.
* </ul>
* <p>
* If <code>b</code> is <code>null</code>,
* a <code>NullPointerException</code> is thrown.
* If <code>off</code> is negative, or <code>len</code>
* is negative, or <code>off+len</code> is
* greater than the length of the array <code>b</code>,
* then an <code>IndexOutOfBoundsException</code>
* is thrown.
* If <code>len</code> is zero,
* then no bytes are read. Otherwise, the first
* byte read is stored into element <code>b[off]</code>,
* the next one into <code>b[off+1]</code>,
* and so on. The number of bytes read is,
* at most, equal to <code>len</code>.
*
* @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</code> 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</code> bytes have been skipped is only one
* possibility.
* This method never throws an <code>EOFException</code>.
* The actual number of bytes skipped is returned.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
int skipBytes(int n) throws IOException;
/**
* Reads one input byte and returns
* <code>true</code> if that byte is nonzero,
* <code>false</code> if that byte is zero.
* This method is suitable for reading
* the byte written by the <code>writeBoolean</code>
* method of interface <code>DataOutput</code>.
*
* @return the <code>boolean</code> 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</code> through <code>127</code>,
* inclusive.
* This method is suitable for
* reading the byte written by the <code>writeByte</code>
* method of interface <code>DataOutput</code>.
*
* @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</code>, and returns
* the result, which is therefore in the range
* <code>0</code>
* through <code>255</code>.
* This method is suitable for reading
* the byte written by the <code>writeByte</code>
* method of interface <code>DataOutput</code>
* if the argument to <code>writeByte</code>
* was intended to be a value in the range
* <code>0</code> through <code>255</code>.
*
* @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</code> value. Let <code>a</code>
* be the first byte read and <code>b</code>
* be the second byte. The value
* returned is:
* <p><pre><code>(short)((a << 8) | (b & 0xff))
* </code></pre>
* This method is suitable for reading the bytes
* written by the <code>writeShort</code> method of
* interface <code>DataOutput</code>.
*
* @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, zero-extends
* it to type <code>int</code>, and returns
* an <code>int</code> value in the range <code>0</code>
* through <code>65535</code>. Let <code>a</code>
* be the first byte read and
* <code>b</code>
* be the second byte. The value returned is:
* <p><pre><code>(((a & 0xff) << 8) | (b & 0xff))
* </code></pre>
* This method is suitable for reading the bytes
* written by the <code>writeShort</code> method
* of interface <code>DataOutput</code> if
* the argument to <code>writeShort</code>
* was intended to be a value in the range
* <code>0</code> through <code>65535</code>.
*
* @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 an input <code>char</code> and returns the <code>char</code> value.
* A Unicode <code>char</code> is made up of two bytes.
* Let <code>a</code>
* be the first byte read and <code>b</code>
* be the second byte. The value
* returned is:
* <p><pre><code>(char)((a << 8) | (b & 0xff))
* </code></pre>
* This method is suitable for reading bytes written by
* the <code>writeChar</code> method of interface
* <code>DataOutput</code>.
*
* @return the Unicode <code>char</code> 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</code> value. Let <code>a</code>
* be the first byte read, <code>b</code> be
* the second byte, <code>c</code> be the third
* byte, and <code>d</code> be the fourth
* byte. The value returned is:
* <p><pre>
* <code>
* (((a & 0xff) << 24) | ((b & 0xff) << 16) |
* ((c & 0xff) << 8) | (d & 0xff))
* </code></pre>
* This method is suitable
* for reading bytes written by the <code>writeInt</code>
* method of interface <code>DataOutput</code>.
*
* @return the <code>int</code> 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</code> value. Let <code>a</code>
* be the first byte read, <code>b</code> be
* the second byte, <code>c</code> be the third
* byte, <code>d</code> be the fourth byte,
* <code>e</code> be the fifth byte, <code>f</code>
* be the sixth byte, <code>g</code> be the
* seventh byte, and <code>h</code> be the
* eighth byte. The value returned is:
* <p><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)))
* </code></pre>
* <p>
* This method is suitable
* for reading bytes written by the <code>writeLong</code>
* method of interface <code>DataOutput</code>.
*
* @return the <code>long</code> 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</code> value. It does this
* by first constructing an <code>int</code>
* value in exactly the manner
* of the <code>readInt</code>
* method, then converting this <code>int</code>
* value to a <code>float</code> in
* exactly the manner of the method <code>Float.intBitsToFloat</code>.
* This method is suitable for reading
* bytes written by the <code>writeFloat</code>
* method of interface <code>DataOutput</code>.
*
* @return the <code>float</code> value read.
* @exception EOFException if this stream reaches the end
* before reading all the bytes.
* @exception IOException if an I/O error occurs.
* @since CLDC 1.1
*/
float readFloat() throws IOException;
/**
* Reads eight input bytes and returns
* a <code>double</code> value. It does this
* by first constructing a <code>long</code>
* value in exactly the manner
* of the <code>readlong</code>
* method, then converting this <code>long</code>
* value to a <code>double</code> in exactly
* the manner of the method <code>Double.longBitsToDouble</code>.
* This method is suitable for reading
* bytes written by the <code>writeDouble</code>
* method of interface <code>DataOutput</code>.
*
* @return the <code>double</code> value read.
* @exception EOFException if this stream reaches the end
* before reading all the bytes.
* @exception IOException if an I/O error occurs.
* @since CLDC 1.1
*/
double readDouble() throws IOException;
/**
* Reads in a string that has been encoded using a modified UTF-8 format.
* The general contract of <code>readUTF</code>
* is that it reads a representation of a Unicode
* character string encoded in Java modified
* UTF-8 format; this string of characters
* is then returned as a <code>String</code>.
* <p>
* First, two bytes are read and used to
* construct an unsigned 16-bit integer in
* exactly the manner of the <code>readUnsignedShort</code>
* 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</code>
* (where <code>x</code> means "may be <code>0</code>
* or <code>1</code>"), 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</code>,
* then the group consists of that byte <code>a</code>
* and a second byte <code>b</code>. If there
* is no byte <code>b</code> (because byte
* <code>a</code> was the last of the bytes
* to be read), or if byte <code>b</code> does
* not match the bit pattern <code>10xxxxxx</code>,
* then a <code>UTFDataFormatException</code>
* is thrown. Otherwise, the group is converted
* to the character:<p>
* <pre><code>(char)(((a& 0x1F) << 6) | (b & 0x3F))
* </code></pre>
* If the first byte of a group
* matches the bit pattern <code>1110xxxx</code>,
* then the group consists of that byte <code>a</code>
* and two more bytes <code>b</code> and <code>c</code>.
* If there is no byte <code>c</code> (because
* byte <code>a</code> was one of the last
* two of the bytes to be read), or either
* byte <code>b</code> or byte <code>c</code>
* does not match the bit pattern <code>10xxxxxx</code>,
* then a <code>UTFDataFormatException</code>
* is thrown. Otherwise, the group is converted
* to the character:<p>
* <pre><code>
* (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))
* </code></pre>
* If the first byte of a group matches the
* pattern <code>1111xxxx</code> or the pattern
* <code>10xxxxxx</code>, then a <code>UTFDataFormatException</code>
* is thrown.
* <p>
* If end of file is encountered
* at any time during this entire process,
* then an <code>EOFException</code> 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</code>,
* which is returned.
* <p>
* The <code>writeUTF</code>
* method of interface <code>DataOutput</code>
* 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 UTF-8 encoding of a string.
*/
String readUTF() throws IOException;
}