769 lines
27 KiB
Java
769 lines
27 KiB
Java
/* DataInputStream.java -- FilteredInputStream that implements DataInput
|
|
Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation
|
|
|
|
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 subclass of <code>FilteredInputStream</code> implements the
|
|
* <code>DataInput</code> interface that provides method for reading primitive
|
|
* Java data types from a stream.
|
|
*
|
|
* @see DataInput
|
|
*
|
|
* @version 0.0
|
|
*
|
|
* @author Warren Levy <warrenl@cygnus.com>
|
|
* @author Aaron M. Renn (arenn@urbanophile.com)
|
|
* @date October 20, 1998.
|
|
*/
|
|
public class DataInputStream extends FilterInputStream implements DataInput
|
|
{
|
|
// readLine() hack to ensure that an '\r' not followed by an '\n' is
|
|
// handled correctly. If set, readLine() will ignore the first char it sees
|
|
// if that char is a '\n'
|
|
boolean ignoreInitialNewline = false;
|
|
|
|
// Byte buffer, used to make primitive read calls more efficient.
|
|
byte[] buf = new byte[8];
|
|
|
|
/**
|
|
* This constructor initializes a new <code>DataInputStream</code>
|
|
* to read from the specified subordinate stream.
|
|
*
|
|
* @param in The subordinate <code>InputStream</code> to read from
|
|
*/
|
|
public DataInputStream(InputStream in)
|
|
{
|
|
super(in);
|
|
}
|
|
|
|
/**
|
|
* This method reads bytes from the underlying stream into the specified
|
|
* byte array buffer. It will attempt to fill the buffer completely, but
|
|
* may return a short count if there is insufficient data remaining to be
|
|
* read to fill the buffer.
|
|
*
|
|
* @param b The buffer into which bytes will be read.
|
|
*
|
|
* @return The actual number of bytes read, or -1 if end of stream reached
|
|
* before reading any bytes.
|
|
*
|
|
* @exception IOException If an error occurs.
|
|
*/
|
|
public final int read(byte[] b) throws IOException
|
|
{
|
|
return in.read(b, 0, b.length);
|
|
}
|
|
|
|
/**
|
|
* This method reads bytes from the underlying stream into the specified
|
|
* byte array buffer. It will attempt to read <code>len</code> bytes and
|
|
* will start storing them at position <code>off</code> into the buffer.
|
|
* This method can return a short count if there is insufficient data
|
|
* remaining to be read to complete the desired read length.
|
|
*
|
|
* @param b The buffer into which bytes will be read.
|
|
* @param off The offset into the buffer to start storing bytes.
|
|
* @param len The requested number of bytes to read.
|
|
*
|
|
* @return The actual number of bytes read, or -1 if end of stream reached
|
|
* before reading any bytes.
|
|
*
|
|
* @exception IOException If an error occurs.
|
|
*/
|
|
public final int read(byte[] b, int off, int len) throws IOException
|
|
{
|
|
return in.read(b, off, len);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
public final boolean readBoolean() throws IOException
|
|
{
|
|
return convertToBoolean(in.read());
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* @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
|
|
*/
|
|
public final byte readByte() throws IOException
|
|
{
|
|
return convertToByte(in.read());
|
|
}
|
|
|
|
/**
|
|
* 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 & 0xFF) << 8) | (byte2 & 0xFF)</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
|
|
*/
|
|
public final char readChar() throws IOException
|
|
{
|
|
readFully (buf, 0, 2);
|
|
return convertToChar(buf);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
public final double readDouble() throws IOException
|
|
{
|
|
return Double.longBitsToDouble(readLong());
|
|
}
|
|
|
|
/**
|
|
* 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 */
|
|
public final float readFloat() throws IOException
|
|
{
|
|
return Float.intBitsToFloat(readInt());
|
|
}
|
|
|
|
/**
|
|
* 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 b 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 */
|
|
public final void readFully(byte[] b) throws IOException
|
|
{
|
|
readFully(b, 0, b.length);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
public final void readFully(byte[] b, int off, int len) throws IOException
|
|
{
|
|
while (len > 0)
|
|
{
|
|
// in.read will block until some data is available.
|
|
int numread = in.read(b, off, len);
|
|
if (numread < 0)
|
|
throw new EOFException();
|
|
len -= numread;
|
|
off += numread;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* 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 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) +
|
|
* ((byte3 & 0xFF) << 8) + (byte4 & 0xFF)))</code>
|
|
* <p>
|
|
* The value returned is in the range of 0 to 65535.
|
|
* <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
|
|
*/
|
|
public final int readInt() throws IOException
|
|
{
|
|
readFully (buf, 0, 4);
|
|
return convertToInt(buf);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @deprecated
|
|
*/
|
|
public final String readLine() throws IOException
|
|
{
|
|
StringBuffer strb = new StringBuffer();
|
|
|
|
readloop: while (true)
|
|
{
|
|
int c = 0;
|
|
char ch = ' ';
|
|
boolean getnext = true;
|
|
while (getnext)
|
|
{
|
|
getnext = false;
|
|
c = in.read();
|
|
if (c < 0) // got an EOF
|
|
return strb.length() > 0 ? strb.toString() : null;
|
|
ch = (char) c;
|
|
if ((ch &= 0xFF) == '\n')
|
|
// hack to correctly handle '\r\n' sequences
|
|
if (ignoreInitialNewline)
|
|
{
|
|
ignoreInitialNewline = false;
|
|
getnext = true;
|
|
}
|
|
else
|
|
break readloop;
|
|
}
|
|
|
|
if (ch == '\r')
|
|
{
|
|
// FIXME: The following code tries to adjust the stream back one
|
|
// character if the next char read is '\n'. As a last resort,
|
|
// it tries to mark the position before reading but the bottom
|
|
// line is that it is possible that this method will not properly
|
|
// deal with a '\r' '\n' combination thus not fulfilling the
|
|
// DataInput contract for readLine. It's not a particularly
|
|
// safe approach threadwise since it is unsynchronized and
|
|
// since it might mark an input stream behind the users back.
|
|
// Along the same vein it could try the same thing for
|
|
// ByteArrayInputStream and PushbackInputStream, but that is
|
|
// probably overkill since this is deprecated & BufferedInputStream
|
|
// is the most likely type of input stream.
|
|
//
|
|
// The alternative is to somehow push back the next byte if it
|
|
// isn't a '\n' or to have the reading methods of this class
|
|
// keep track of whether the last byte read was '\r' by readLine
|
|
// and then skip the very next byte if it is '\n'. Either way,
|
|
// this would increase the complexity of the non-deprecated methods
|
|
// and since it is undesirable to make non-deprecated methods
|
|
// less efficient, the following seems like the most reasonable
|
|
// approach.
|
|
int next_c = 0;
|
|
char next_ch = ' ';
|
|
if (in instanceof BufferedInputStream)
|
|
{
|
|
next_c = in.read();
|
|
next_ch = (char) (next_c & 0xFF);
|
|
if ((next_ch != '\n') && (next_c >= 0))
|
|
{
|
|
BufferedInputStream bin = (BufferedInputStream) in;
|
|
if (bin.pos > 0)
|
|
bin.pos--;
|
|
}
|
|
}
|
|
else if (markSupported())
|
|
{
|
|
next_c = in.read();
|
|
next_ch = (char) (next_c & 0xFF);
|
|
if ((next_ch != '\n') && (next_c >= 0))
|
|
{
|
|
mark(1);
|
|
if ((in.read() & 0xFF) != '\n')
|
|
reset();
|
|
}
|
|
}
|
|
// In order to catch cases where 'in' isn't a BufferedInputStream
|
|
// and doesn't support mark() (such as reading from a Socket), set
|
|
// a flag that instructs readLine() to ignore the first character
|
|
// it sees _if_ that character is a '\n'.
|
|
else ignoreInitialNewline = true;
|
|
break;
|
|
}
|
|
strb.append(ch);
|
|
}
|
|
|
|
return strb.length() > 0 ? strb.toString() : "";
|
|
}
|
|
|
|
/**
|
|
* This method reads a Java long 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)((((long)byte1 & 0xFF) << 56) + (((long)byte2 & 0xFF) << 48) +
|
|
* (((long)byte3 & 0xFF) << 40) + (((long)byte4 & 0xFF) << 32) +
|
|
* (((long)byte5 & 0xFF) << 24) + (((long)byte6 & 0xFF) << 16) +
|
|
* (((long)byte7 & 0xFF) << 8) + ((long)byte9 & 0xFF)))</code>
|
|
* <p>
|
|
* The value returned is in the range of 0 to 65535.
|
|
* <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
|
|
*/
|
|
public final long readLong() throws IOException
|
|
{
|
|
readFully (buf, 0, 8);
|
|
return convertToLong(buf);
|
|
}
|
|
|
|
/**
|
|
* 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 & 0xFF) << 8) | (byte2 & 0xFF)</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
|
|
*/
|
|
public final short readShort() throws IOException
|
|
{
|
|
readFully (buf, 0, 2);
|
|
return convertToShort(buf);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
public final int readUnsignedByte() throws IOException
|
|
{
|
|
return convertToUnsignedByte(in.read());
|
|
}
|
|
|
|
/**
|
|
* 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 & 0xFF) << 8) + (byte2 & 0xFF))</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
|
|
*/
|
|
public final int readUnsignedShort() throws IOException
|
|
{
|
|
readFully (buf, 0, 2);
|
|
return convertToUnsignedShort(buf);
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
* <p>
|
|
* 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:
|
|
* <p>
|
|
* <code>(char)(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) | (byte3 & 0x3F))</code>
|
|
* <p>
|
|
* 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>\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
|
|
*/
|
|
public final String readUTF() throws IOException
|
|
{
|
|
return readUTF(this);
|
|
}
|
|
|
|
/**
|
|
* This method reads a String encoded in UTF-8 format from the
|
|
* specified <code>DataInput</code> source.
|
|
*
|
|
* @param in The <code>DataInput</code> source to read from
|
|
*
|
|
* @return The String read from the source
|
|
*
|
|
* @exception IOException If an error occurs
|
|
*/
|
|
public final static String readUTF(DataInput in) throws IOException
|
|
{
|
|
final int UTFlen = in.readUnsignedShort();
|
|
byte[] buf = new byte[UTFlen];
|
|
|
|
// This blocks until the entire string is available rather than
|
|
// doing partial processing on the bytes that are available and then
|
|
// blocking. An advantage of the latter is that Exceptions
|
|
// could be thrown earlier. The former is a bit cleaner.
|
|
in.readFully(buf, 0, UTFlen);
|
|
|
|
return convertFromUTF(buf);
|
|
}
|
|
|
|
/**
|
|
* This method attempts to skip and discard the specified number of bytes
|
|
* in the input stream. It may actually skip fewer bytes than requested.
|
|
* This method will not skip any bytes if passed a negative number of bytes
|
|
* to skip.
|
|
*
|
|
* @param n The requested number of bytes to skip.
|
|
* @return The requested number of bytes to skip.
|
|
* @exception IOException If an error occurs.
|
|
* @specnote The JDK docs claim that this returns the number of bytes
|
|
* actually skipped. The JCL claims that this method can throw an
|
|
* EOFException. Neither of these appear to be true in the JDK 1.3's
|
|
* implementation. This tries to implement the actual JDK behaviour.
|
|
*/
|
|
public final int skipBytes(int n) throws IOException
|
|
{
|
|
if (n <= 0)
|
|
return 0;
|
|
try
|
|
{
|
|
return (int) in.skip(n);
|
|
}
|
|
catch (EOFException x)
|
|
{
|
|
// do nothing.
|
|
}
|
|
return n;
|
|
}
|
|
|
|
static boolean convertToBoolean(int b) throws EOFException
|
|
{
|
|
if (b < 0)
|
|
throw new EOFException();
|
|
return (b != 0);
|
|
}
|
|
|
|
static byte convertToByte(int i) throws EOFException
|
|
{
|
|
if (i < 0)
|
|
throw new EOFException();
|
|
return (byte) i;
|
|
}
|
|
|
|
static int convertToUnsignedByte(int i) throws EOFException
|
|
{
|
|
if (i < 0)
|
|
throw new EOFException();
|
|
return (i & 0xFF);
|
|
}
|
|
|
|
static char convertToChar(byte[] buf)
|
|
{
|
|
return (char) ((buf[0] << 8) | (buf[1] & 0xff));
|
|
}
|
|
|
|
static short convertToShort(byte[] buf)
|
|
{
|
|
return (short) ((buf[0] << 8) | (buf[1] & 0xff));
|
|
}
|
|
|
|
static int convertToUnsignedShort(byte[] buf)
|
|
{
|
|
return (((buf[0] & 0xff) << 8) | (buf[1] & 0xff));
|
|
}
|
|
|
|
static int convertToInt(byte[] buf)
|
|
{
|
|
return (((buf[0] & 0xff) << 24) | ((buf[1] & 0xff) << 16) |
|
|
((buf[2] & 0xff) << 8) | (buf[3] & 0xff));
|
|
}
|
|
|
|
static long convertToLong(byte[] buf)
|
|
{
|
|
return (((long)(buf[0] & 0xff) << 56) |
|
|
((long)(buf[1] & 0xff) << 48) |
|
|
((long)(buf[2] & 0xff) << 40) |
|
|
((long)(buf[3] & 0xff) << 32) |
|
|
((long)(buf[4] & 0xff) << 24) |
|
|
((long)(buf[5] & 0xff) << 16) |
|
|
((long)(buf[6] & 0xff) << 8) |
|
|
((long)(buf[7] & 0xff)));
|
|
}
|
|
|
|
static String convertFromUTF(byte[] buf)
|
|
throws EOFException, UTFDataFormatException
|
|
{
|
|
StringBuffer strbuf = new StringBuffer();
|
|
|
|
for (int i = 0; i < buf.length; )
|
|
{
|
|
if ((buf[i] & 0x80) == 0) // bit pattern 0xxxxxxx
|
|
strbuf.append((char) (buf[i++] & 0xFF));
|
|
else if ((buf[i] & 0xE0) == 0xC0) // bit pattern 110xxxxx
|
|
{
|
|
if (i + 1 >= buf.length || (buf[i+1] & 0xC0) != 0x80)
|
|
throw new UTFDataFormatException();
|
|
|
|
strbuf.append((char) (((buf[i++] & 0x1F) << 6) |
|
|
(buf[i++] & 0x3F)));
|
|
}
|
|
else if ((buf[i] & 0xF0) == 0xE0) // bit pattern 1110xxxx
|
|
{
|
|
if (i + 2 >= buf.length ||
|
|
(buf[i+1] & 0xC0) != 0x80 || (buf[i+2] & 0xC0) != 0x80)
|
|
throw new UTFDataFormatException();
|
|
|
|
strbuf.append((char) (((buf[i++] & 0x0F) << 12) |
|
|
((buf[i++] & 0x3F) << 6) |
|
|
(buf[i++] & 0x3F)));
|
|
}
|
|
else // must be ((buf[i] & 0xF0) == 0xF0 || (buf[i] & 0xC0) == 0x80)
|
|
throw new UTFDataFormatException(); // bit patterns 1111xxxx or
|
|
// 10xxxxxx
|
|
}
|
|
|
|
return strbuf.toString();
|
|
}
|
|
}
|