473 lines
18 KiB
Java
473 lines
18 KiB
Java
/* DataInput.java -- Interface for reading data from a stream
|
|
Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath 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 for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA.
|
|
|
|
Linking this library statically or dynamically with other modules is
|
|
making a combined work based on this library. Thus, the terms and
|
|
conditions of the GNU General Public License cover the whole
|
|
combination.
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent
|
|
modules, and to copy and distribute the resulting executable under
|
|
terms of your choice, provided that you also meet, for each linked
|
|
independent module, the terms and conditions of the license of that
|
|
module. An independent module is a module which is not derived from
|
|
or based on this library. If you modify this library, you may extend
|
|
this exception to your version of the library, but you are not
|
|
obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version. */
|
|
|
|
|
|
package java.io;
|
|
|
|
/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
|
|
* "The Java Language Specification", ISBN 0-201-63451-1
|
|
* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
|
|
* Status: Believed complete and correct.
|
|
*/
|
|
|
|
/**
|
|
* This interface is implemented by classes that can data from streams
|
|
* into Java primitive types.
|
|
*
|
|
* @author Aaron M. Renn (arenn@urbanophile.com)
|
|
* @author Warren Levy <warrenl@cygnus.com>
|
|
*/
|
|
public interface DataInput
|
|
{
|
|
|
|
/**
|
|
* This method reads a Java boolean value from an input stream. It does
|
|
* so by reading a single byte of data. If that byte is zero, then the
|
|
* value returned is <code>false</code>. If the byte is non-zero, then
|
|
* the value returned is <code>true</code>.
|
|
* <p>
|
|
* This method can read a <code>boolean</code> written by an object
|
|
* implementing the <code>writeBoolean()</code> method in the
|
|
* <code>DataOutput</code> interface.
|
|
*
|
|
* @return The <code>boolean</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the boolean
|
|
* @exception IOException If any other error occurs
|
|
*/
|
|
boolean
|
|
readBoolean() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a Java byte value from an input stream. The value
|
|
* is in the range of -128 to 127.
|
|
* <p>
|
|
* This method can read a <code>byte</code> written by an object
|
|
* implementing the
|
|
* <code>writeByte()</code> method in the <code>DataOutput</code> interface.
|
|
* <p>
|
|
* @return The <code>byte</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the byte
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
byte
|
|
readByte() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads 8 unsigned bits into a Java <code>int</code> value from
|
|
* the stream. The value returned is in the range of 0 to 255.
|
|
* <p>
|
|
* This method can read an unsigned byte written by an object implementing the
|
|
* <code>writeUnsignedByte()</code> method in the <code>DataOutput</code>
|
|
* interface.
|
|
*
|
|
* @return The unsigned bytes value read as a Java <code>int</code>.
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the value
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
int
|
|
readUnsignedByte() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a Java <code>char</code> value from an input stream.
|
|
* It operates by reading two bytes from the stream and converting them to
|
|
* a single 16-bit Java <code>char</code>. The two bytes are stored most
|
|
* significant byte first (i.e., "big endian") regardless of the native
|
|
* host byte ordering.
|
|
* <p>
|
|
* As an example, if <code>byte1</code> and <code>byte2</code> represent the
|
|
* first and second byte read from the stream respectively, they will be
|
|
* transformed to a <code>char</code> in the following manner:
|
|
* <p>
|
|
* <code>(char)((byte1 << 8) + byte2)</code>
|
|
* <p>
|
|
* This method can read a <code>char</code> written by an object implementing
|
|
* the
|
|
* <code>writeChar()</code> method in the <code>DataOutput</code> interface.
|
|
*
|
|
* @return The <code>char</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the char
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
char
|
|
readChar() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a signed 16-bit value into a Java in from the stream.
|
|
* It operates by reading two bytes from the stream and converting them to
|
|
* a single 16-bit Java <code>short</code>. The two bytes are stored most
|
|
* significant byte first (i.e., "big endian") regardless of the native
|
|
* host byte ordering.
|
|
* <p>
|
|
* As an example, if <code>byte1</code> and <code>byte2</code> represent the
|
|
* first and second byte read from the stream respectively, they will be
|
|
* transformed to a <code>short</code> in the following manner:
|
|
* <p>
|
|
* <code>(short)((byte1 << 8) + byte2)</code>
|
|
* <p>
|
|
* The value returned is in the range of -32768 to 32767.
|
|
* <p>
|
|
* This method can read a <code>short</code> written by an object implementing
|
|
* the <code>writeShort()</code> method in the <code>DataOutput</code>
|
|
* interface.
|
|
*
|
|
* @return The <code>short</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the value
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
short
|
|
readShort() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads 16 unsigned bits into a Java int value from the stream.
|
|
* It operates by reading two bytes from the stream and converting them to
|
|
* a single Java <code>int</code>. The two bytes are stored most
|
|
* significant byte first (i.e., "big endian") regardless of the native
|
|
* host byte ordering.
|
|
* <p>
|
|
* As an example, if <code>byte1</code> and <code>byte2</code> represent the
|
|
* first and second byte read from the stream respectively, they will be
|
|
* transformed to an <code>int</code> in the following manner:
|
|
* <p>
|
|
* <code>(int)((byte1 << 8) + byte2)</code>
|
|
* <p>
|
|
* The value returned is in the range of 0 to 65535.
|
|
* <p>
|
|
* This method can read an unsigned short written by an object implementing
|
|
* the <code>writeUnsignedShort()</code> method in the <code>DataOutput</code>
|
|
* interface.
|
|
*
|
|
* @return The unsigned short value read as a Java <code>int</code>.
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the value
|
|
* @exception IOException If any other error occurs
|
|
*/
|
|
int
|
|
readUnsignedShort() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a Java <code>int</code> value from an input stream
|
|
* It operates by reading four bytes from the stream and converting them to
|
|
* a single Java <code>int</code>. The bytes are stored most
|
|
* significant byte first (i.e., "big endian") regardless of the native
|
|
* host byte ordering.
|
|
* <p>
|
|
* As an example, if <code>byte1</code> through <code>byte4</code> represent
|
|
* the first four bytes read from the stream, they will be
|
|
* transformed to an <code>int</code> in the following manner:
|
|
* <p>
|
|
* <code>(int)((byte1 << 24) + (byte2 << 16) + (byte3 << 8) + byte4))</code>
|
|
* <p>
|
|
The value returned is in the range of -2147483648 to 2147483647.
|
|
* <p>
|
|
* This method can read an <code>int</code> written by an object implementing
|
|
* the <code>writeInt()</code> method in the <code>DataOutput</code> interface.
|
|
*
|
|
* @return The <code>int</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the int
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
int
|
|
readInt() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a Java <code>long</code> value from an input stream
|
|
* It operates by reading eight bytes from the stream and converting them to
|
|
* a single Java <code>long</code>. The bytes are stored most
|
|
* significant byte first (i.e., "big endian") regardless of the native
|
|
* host byte ordering.
|
|
* <p>
|
|
* As an example, if <code>byte1</code> through <code>byte8</code> represent
|
|
* the first eight bytes read from the stream, they will be
|
|
* transformed to an <code>long</code> in the following manner:
|
|
* <p>
|
|
* <code>(long)((byte1 << 56) + (byte2 << 48) + (byte3 << 40) +
|
|
* (byte4 << 32) + (byte5 << 24) + (byte6 << 16) + (byte7 << 8) + byte9))
|
|
* </code>
|
|
* <p>
|
|
* The value returned is in the range of -9223372036854775808 to
|
|
* 9223372036854775807.
|
|
* <p>
|
|
* This method can read an <code>long</code> written by an object implementing
|
|
* the <code>writeLong()</code> method in the <code>DataOutput</code>
|
|
* interface.
|
|
*
|
|
* @return The <code>long</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the long
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
long
|
|
readLong() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a Java float value from an input stream. It operates
|
|
* by first reading an <code>int</code> value from the stream by calling the
|
|
* <code>readInt()</code> method in this interface, then converts that
|
|
* <code>int</code> to a <code>float</code> using the
|
|
* <code>intBitsToFloat</code> method in the class
|
|
* <code>java.lang.Float</code>.
|
|
* <p>
|
|
* This method can read a <code>float</code> written by an object implementing
|
|
* the <code>writeFloat()</code> method in the <code>DataOutput</code>
|
|
* interface.
|
|
*
|
|
* @return The <code>float</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the float
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see java.lang.Float
|
|
* @see DataOutput
|
|
*/
|
|
float
|
|
readFloat() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a Java double value from an input stream. It operates
|
|
* by first reading a <code>long</code> value from the stream by calling the
|
|
* <code>readLong()</code> method in this interface, then converts that
|
|
* <code>long</code> to a <code>double</code> using the
|
|
* <code>longBitsToDouble</code> method in the class
|
|
* <code>java.lang.Double</code>.
|
|
* <p>
|
|
* This method can read a <code>double</code> written by an object
|
|
* implementing the <code>writeDouble()</code> method in the
|
|
* <code>DataOutput</code> interface.
|
|
*
|
|
* @return The <code>double</code> value read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the double
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see java.lang.Double
|
|
* @see DataOutput
|
|
*/
|
|
double
|
|
readDouble() throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads the next line of text data from an input stream.
|
|
* It operates by reading bytes and converting those bytes to <code>char</code>
|
|
* values by treating the byte read as the low eight bits of the
|
|
* <code>char</code> and using 0 as the high eight bits. Because of this,
|
|
* it does not support the full 16-bit Unicode character set.
|
|
* <P>
|
|
* The reading of bytes ends when either the end of file or a line terminator
|
|
* is encountered. The bytes read are then returned as a <code>String</code>.
|
|
* A line terminator is a byte sequence consisting of either
|
|
* <code>\r</code>, <code>\n</code> or <code>\r\n</code>. These termination
|
|
* charaters are discarded and are not returned as part of the string.
|
|
* <p>
|
|
* This method can read data that was written by an object implementing the
|
|
* <code>writeLine()</code> method in <code>DataOutput</code>.
|
|
*
|
|
* @return The line read as a <code>String</code>
|
|
*
|
|
* @exception IOException If an error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
String
|
|
readLine() throws IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads a <code>String</code> from an input stream that is
|
|
* encoded in a modified UTF-8 format. This format has a leading two byte
|
|
* sequence that contains the remaining number of bytes to read. This two byte
|
|
* sequence is read using the <code>readUnsignedShort()</code> method of this
|
|
* interface.
|
|
*
|
|
* After the number of remaining bytes have been determined, these bytes
|
|
* are read an transformed into <code>char</code> values. These
|
|
* <code>char</code> values are encoded in the stream using either a one, two,
|
|
* or three byte format.
|
|
* The particular format in use can be determined by examining the first
|
|
* byte read.
|
|
* <p>
|
|
* If the first byte has a high order bit of 0, then
|
|
* that character consists on only one byte. This character value consists
|
|
* of seven bits that are at positions 0 through 6 of the byte. As an
|
|
* example, if <code>byte1</code> is the byte read from the stream, it would
|
|
* be converted to a <code>char</code> like so:
|
|
* <p>
|
|
* <code>(char)byte1</code>
|
|
* <p>
|
|
* If the first byte has 110 as its high order bits, then the
|
|
* character consists of two bytes. The bits that make up the character
|
|
* value are in positions 0 through 4 of the first byte and bit positions
|
|
* 0 through 5 of the second byte. (The second byte should have
|
|
* 10 as its high order bits). These values are in most significant
|
|
* byte first (i.e., "big endian") order.
|
|
* <p>
|
|
* As an example, if <code>byte1</code> and <code>byte2</code> are the first
|
|
* two bytes read respectively, and the high order bits of them match the
|
|
* patterns which indicate a two byte character encoding, then they would be
|
|
* converted to a Java <code>char</code> like so:
|
|
* <p>
|
|
* <code>(char)(((byte1 & 0x1F) << 6) + (byte2 & 0x3F))</code>
|
|
* <p>
|
|
* If the first byte has a 1110 as its high order bits, then the
|
|
* character consists of three bytes. The bits that make up the character
|
|
* value are in positions 0 through 3 of the first byte and bit positions
|
|
* 0 through 5 of the other two bytes. (The second and third bytes should
|
|
* have 10 as their high order bits). These values are in most
|
|
* significant byte first (i.e., "big endian") order.
|
|
* <p>
|
|
* As an example, if <code>byte1</code>, <code>byte2</code>, and
|
|
* <code>byte3</code> are the three bytes read, and the high order bits of
|
|
* them match the patterns which indicate a three byte character encoding,
|
|
* then they would be converted to a Java <code>char</code> like so:
|
|
*
|
|
* <code>
|
|
* (char)(((byte1 & 0x0F) << 12) + ((byte2 & 0x3F) + (byte3 & 0x3F))
|
|
* </code>
|
|
*
|
|
* Note that all characters are encoded in the method that requires the
|
|
* fewest number of bytes with the exception of the character with the
|
|
* value of <code>\<llll>u0000</code> which is encoded as two bytes. This is
|
|
* a modification of the UTF standard used to prevent C language style
|
|
* <code>NUL</code> values from appearing in the byte stream.
|
|
* <p>
|
|
* This method can read data that was written by an object implementing the
|
|
* <code>writeUTF()</code> method in <code>DataOutput</code>.
|
|
*
|
|
* @returns The <code>String</code> read
|
|
*
|
|
* @exception EOFException If end of file is reached before reading the String
|
|
* @exception UTFDataFormatException If the data is not in UTF-8 format
|
|
* @exception IOException If any other error occurs
|
|
*
|
|
* @see DataOutput
|
|
*/
|
|
String
|
|
readUTF() throws EOFException, UTFDataFormatException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads raw bytes into the passed array until the array is
|
|
* full. Note that this method blocks until the data is available and
|
|
* throws an exception if there is not enough data left in the stream to
|
|
* fill the buffer
|
|
*
|
|
* @param buf The buffer into which to read the data
|
|
*
|
|
* @exception EOFException If end of file is reached before filling the buffer
|
|
* @exception IOException If any other error occurs
|
|
*/
|
|
void
|
|
readFully(byte[] buf) throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method reads raw bytes into the passed array <code>buf</code> starting
|
|
* <code>offset</code> bytes into the buffer. The number of bytes read will be
|
|
* exactly <code>len</code>. Note that this method blocks until the data is
|
|
* available and * throws an exception if there is not enough data left in
|
|
* the stream to read <code>len</code> bytes.
|
|
*
|
|
* @param buf The buffer into which to read the data
|
|
* @param offset The offset into the buffer to start storing data
|
|
* @param len The number of bytes to read into the buffer
|
|
*
|
|
* @exception EOFException If end of file is reached before filling the buffer
|
|
* @exception IOException If any other error occurs
|
|
*/
|
|
void
|
|
readFully(byte[] buf, int offset, int len) throws EOFException, IOException;
|
|
|
|
/*************************************************************************/
|
|
|
|
/**
|
|
* This method skips and discards the specified number of bytes in an
|
|
* input stream
|
|
*
|
|
* @param num_bytes The number of bytes to skip
|
|
*
|
|
* @return The number of bytes actually skipped, which will always be
|
|
* <code>num_bytes</code>
|
|
*
|
|
* @exception EOFException If end of file is reached before all bytes can be
|
|
* skipped
|
|
* @exception IOException If any other error occurs
|
|
*/
|
|
int
|
|
skipBytes(int n) throws EOFException, IOException;
|
|
|
|
} // interface DataInput
|