com.sun.xfile
Class XRandomAccessFile

java.lang.Object
  com.sun.xfile.XRandomAccessFile

All Implemented Interfaces:

java.io.DataInput, java.io.DataOutput

public class XRandomAccessFile
extends java.lang.Object
implements java.io.DataOutput, java.io.DataInput

Instances of this class support both reading and writing to a random access file. An application can modify the position in the file at which the next read or write occurs. This class provides a sense of security by offering methods that allow specified mode accesses of read-only or read-write to files.

Constructor Summary

XRandomAccessFile(java.lang.String name, java.lang.String mode)
Creates a random access file to read from, and optionally to write to, a file with the specified name.

XRandomAccessFile(XFile xf, java.lang.String mode)
Creates a random access file stream to read from, and optionally to write to, the file specified by the XFile argument.

Method Summary

void	close() Closes this random access file and flushes any unwritten data to the file.
void	flush() Forces any buffered output bytes to be written out.
long	getFilePointer() Returns the current offset in this file.
long	length() Returns the length of this file.
int	read() Reads a byte of data from this file.
int	read(byte[] b) Reads up to b.length bytes of data from this file into an array of bytes.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from this file into an array of bytes.
boolean	readBoolean() Reads a boolean from this file.
byte	readByte() Reads a signed 8-bit value from this file.
char	readChar() Reads a Unicode character from this file.
double	readDouble() Reads a double from this file.
float	readFloat() Reads a float from this file.
void	readFully(byte[] b) Reads b.length bytes from this file into the byte array.
void	readFully(byte[] b, int off, int len) Reads exactly len bytes from this file into the byte array.
int	readInt() Reads a signed 32-bit integer from this file.
java.lang.String	readLine() Reads the next line of text from this file.
long	readLong() Reads a signed 64-bit integer from this file.
short	readShort() Reads a signed 16-bit number from this file.
int	readUnsignedByte() Reads an unsigned 8-bit number from this file.
int	readUnsignedShort() Reads an unsigned 16-bit number from this file.
java.lang.String	readUTF() Reads in a string from this file.
void	seek(long pos) Sets the offset from the beginning of this file at which the next read or write occurs.
int	skipBytes(int n) Skips exactly n bytes of input.
void	write(byte[] b) Writes b.length bytes from the specified byte array starting at offset off to this file.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this file.
void	write(int b) Writes the specified byte to this file.
void	writeBoolean(boolean v) Writes a boolean to the file as a 1-byte value.
void	writeByte(int v) Writes a byte to the file as a 1-byte value.
void	writeBytes(java.lang.String s) Writes the string to the file as a sequence of bytes.
void	writeChar(int v) Writes a char to the file as a 2-byte value, high byte first.
void	writeChars(java.lang.String s) Writes a string to the file as a sequence of characters.
void	writeDouble(double v) Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.
void	writeFloat(float v) Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.
void	writeInt(int v) Writes an int to the file as four bytes, high byte first.
void	writeLong(long v) Writes a long to the file as eight bytes, high byte first.
void	writeShort(int v) Writes a short to the file as two bytes, high byte first.
void	writeUTF(java.lang.String str) Writes a string to the file using UTF-8 encoding in a machine-independent manner.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

XRandomAccessFile

public XRandomAccessFile(XFile xf,
                         java.lang.String mode)
                  throws java.io.IOException

Creates a random access file stream to read from, and optionally to write to, the file specified by the XFile argument. The mode argument must either be equal to "r" or to "rw", indicating either to open the file for input, or for both input and output, respectively.

Parameters:

xf - the XFile object.

mode - the access mode.

Throws:

java.lang.IllegalArgumentException - if the mode argument is not equal to "r" or to "rw".

java.io.IOException - if an I/O error occurs.

XRandomAccessFile

public XRandomAccessFile(java.lang.String name,
                         java.lang.String mode)
                  throws java.io.IOException

Creates a random access file to read from, and optionally to write to, a file with the specified name.

The mode argument must either be equal to "r" or "rw", indicating either to open the file for input or for both input and output.

Parameters:

name - the native or URL file name.

mode - the access mode.

Throws:

java.lang.IllegalArgumentException - if the mode argument is not equal to "r" or to "rw".

java.io.IOException - if an I/O error occurs.

Method Detail

read

public int read()
         throws java.io.IOException

Reads a byte of data from this file.

Returns:

the next byte of data, or -1 if the end of the file is reached.

Throws:

java.io.IOException - if an I/O error occurs.

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException

Reads up to len bytes of data from this file into an array of bytes.

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the maximum number of bytes read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.

Throws:

java.io.IOException - if an I/O error occurs.

read

public int read(byte[] b)
         throws java.io.IOException

Reads up to b.length bytes of data from this file into an array of bytes.

Parameters:

b - the buffer into which the data is read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of this file has been reached.

Throws:

java.io.IOException - if an I/O error occurs.

readFully

public final void readFully(byte[] b)
                     throws java.io.IOException

Reads b.length bytes from this file into the byte array.

Specified by:

readFully in interface java.io.DataInput

Parameters:

b - the buffer into which the data is read.

Throws:

java.io.EOFException - if this file reaches the end before reading all the bytes.

java.io.IOException - if an I/O error occurs.

readFully

public final void readFully(byte[] b,
                            int off,
                            int len)
                     throws java.io.IOException

Reads exactly len bytes from this file into the byte array.

Specified by:

readFully in interface java.io.DataInput

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the number of bytes to read.

Throws:

java.io.EOFException - if this file reaches the end before reading all the bytes.

java.io.IOException - if an I/O error occurs.

skipBytes

public int skipBytes(int n)
              throws java.io.IOException

Skips exactly n bytes of input.

Specified by:

skipBytes in interface java.io.DataInput

Parameters:

n - the number of bytes to be skipped.

Returns:

the number of bytes skipped, which is always n.

Throws:

java.io.EOFException - if this file reaches the end before skipping all the bytes.

java.io.IOException - if an I/O error occurs.

write

public void write(int b)
           throws java.io.IOException

Writes the specified byte to this file.

Specified by:

write in interface java.io.DataOutput

Parameters:

b - the byte to be written.

Throws:

java.io.IOException - if an I/O error occurs.

write

public void write(byte[] b)
           throws java.io.IOException

Writes b.length bytes from the specified byte array starting at offset off to this file.

Specified by:

write in interface java.io.DataOutput

Parameters:

b - the data.

Throws:

java.io.IOException - if an I/O error occurs.

write

public void write(byte[] b,
                  int off,
                  int len)
           throws java.io.IOException

Writes len bytes from the specified byte array starting at offset off to this file.

Specified by:

write in interface java.io.DataOutput

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

java.io.IOException - if an I/O error occurs.

getFilePointer

public long getFilePointer()
                    throws java.io.IOException

Returns the current offset in this file.

Returns:

the offset from the beginning of the file, in bytes, at which the next read or write occurs.

Throws:

java.io.IOException - if an I/O error occurs.

seek

public void seek(long pos)
          throws java.io.IOException

Sets the offset from the beginning of this file at which the next read or write occurs.

Parameters:

pos - the absolute position.

Throws:

java.io.IOException - if an I/O error occurs.

length

public long length()
            throws java.io.IOException

Returns the length of this file.

Returns:

the length of this file.

Throws:

java.io.IOException - if an I/O error occurs.

flush

public void flush()
           throws java.io.IOException

Forces any buffered output bytes to be written out.

Throws:

java.io.IOException - if an I/O error occurs.

close

public void close()
           throws java.io.IOException

Closes this random access file and flushes any unwritten data to the file. After the file is closed further I/O operations may throw IOException.

Throws:

java.io.IOException - if an I/O error occurs.

readBoolean

public final boolean readBoolean()
                          throws java.io.IOException

Reads a boolean from this file. This method reads a single byte from the file. A value of 0 represents false. Any other value represents true. This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:

readBoolean in interface java.io.DataInput

Returns:

the boolean value read.

Throws:

java.io.EOFException - if this file has reached the end.

java.io.IOException - if an I/O error occurs.

readByte

public final byte readByte()
                    throws java.io.IOException

Reads a signed 8-bit value from this file. This method reads a byte from the file. If the byte read is b, where 0 <= b <= 255, then the result is:

(byte)(b)

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:

readByte in interface java.io.DataInput

Returns:

the next byte of this file as a signed 8-bit byte.

Throws:

java.io.EOFException - if this file has reached the end.

java.io.IOException - if an I/O error occurs.

readUnsignedByte

public final int readUnsignedByte()
                           throws java.io.IOException

Reads an unsigned 8-bit number from this file. This method reads a byte from this file and returns that byte.

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:

readUnsignedByte in interface java.io.DataInput

Returns:

the next byte of this file, interpreted as an unsigned 8-bit number.

Throws:

java.io.EOFException - if this file has reached the end.

java.io.IOException - if an I/O error occurs.

readShort

public final short readShort()
                      throws java.io.IOException

Reads a signed 16-bit number from this file. The method reads 2 bytes from this file. If the two bytes read, in order, are b1 and b2, where each of the two values is between 0 and 255, inclusive, then the result is equal to:

(short)((b1 << 8) | b2)

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readShort in interface java.io.DataInput

Returns:

the next two bytes of this file, interpreted as a signed 16-bit number.

Throws:

java.io.EOFException - if this file reaches the end before reading two bytes.

java.io.IOException - if an I/O error occurs.

readUnsignedShort

public final int readUnsignedShort()
                            throws java.io.IOException

Reads an unsigned 16-bit number from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

(b1 << 8) | b2

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readUnsignedShort in interface java.io.DataInput

Returns:

the next two bytes of this file, interpreted as an unsigned 16-bit integer.

Throws:

java.io.EOFException - if this file reaches the end before reading two bytes.

java.io.IOException - if an I/O error occurs.

readChar

public final char readChar()
                    throws java.io.IOException

Reads a Unicode character from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

(char)((b1 << 8) | b2)

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readChar in interface java.io.DataInput

Returns:

the next two bytes of this file as a Unicode character.

Throws:

java.io.EOFException - if this file reaches the end before reading two bytes.

java.io.IOException - if an I/O error occurs.

readInt

public final int readInt()
                  throws java.io.IOException

Reads a signed 32-bit integer from this file. This method reads 4 bytes from the file. If the bytes read, in order, are b1, b2, b3, and b4, where 0 <= b1, b2, b3, b4 <= 255, then the result is equal to:

(b1 << 24) | (b2 << 16) + (b3 << 8) + b4

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readInt in interface java.io.DataInput

Returns:

the next four bytes of this file, interpreted as an int.

Throws:

java.io.EOFException - if this file reaches the end before reading four bytes.

java.io.IOException - if an I/O error occurs.

readLong

public final long readLong()
                    throws java.io.IOException

Reads a signed 64-bit integer from this file. This method reads eight bytes from the file. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, where:

0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,

then the result is equal to:

     ((long)b1 << 56) + ((long)b2 << 48)
     + ((long)b3 << 40) + ((long)b4 << 32)
     + ((long)b5 << 24) + ((long)b6 << 16)
     + ((long)b7 << 8) + b8
 

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readLong in interface java.io.DataInput

Returns:

the next eight bytes of this file, interpreted as a long.

Throws:

java.io.EOFException - if this file reaches the end before reading eight bytes.

java.io.IOException - if an I/O error occurs.

readFloat

public final float readFloat()
                      throws java.io.IOException

Reads a float from this file. This method reads an int value as if by the readInt method and then converts that int to a float using the intBitsToFloat method in class Float.

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readFloat in interface java.io.DataInput

Returns:

the next four bytes of this file, interpreted as a float.

Throws:

java.io.EOFException - if this file reaches the end before reading four bytes.

java.io.IOException - if an I/O error occurs.

See Also:

readInt(), Float.intBitsToFloat(int)

readDouble

public final double readDouble()
                        throws java.io.IOException

Reads a double from this file. This method reads a long value as if by the readLong method and then converts that long to a double using the longBitsToDouble method in class Double.

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readDouble in interface java.io.DataInput

Returns:

the next eight bytes of this file, interpreted as a double.

Throws:

java.io.EOFException - if this file reaches the end before reading eight bytes.

java.io.IOException - if an I/O error occurs.

See Also:

readLong(), Double.longBitsToDouble(long)

readLine

public final java.lang.String readLine()
                                throws java.io.IOException

Reads the next line of text from this file. This method successively reads bytes from the file until it reaches the end of a line of text.

A line of text is terminated by a carriage-return character ('\r'), a newline character ('\n'), a carriage-return character immediately followed by a newline character, or the end of the input stream. The line-terminating character(s), if any, are included as part of the string returned.

This method blocks until a newline character is read, a carriage return and the byte following it are read (to see if it is a newline), the end of the stream is detected, or an exception is thrown.

Specified by:

readLine in interface java.io.DataInput

Returns:

the next line of text from this file.

Throws:

java.io.IOException - if an I/O error occurs.

readUTF

public final java.lang.String readUTF()
                               throws java.io.IOException

Reads in a string from this file. The string has been encoded using a modified UTF-8 format.

The first two bytes are read as if by readUnsignedShort. This value gives the number of following bytes that are in the encoded string, not the length of the resulting string. The following bytes are then interpreted as bytes encoding characters in the UTF-8 format and are converted into characters.

This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:

readUTF in interface java.io.DataInput

Returns:

a Unicode string.

Throws:

java.io.EOFException - if this file reaches the end before reading all the bytes.

java.io.IOException - if an I/O error occurs.

java.io.UTFDataFormatException - if the bytes do not represent valid UTF-8 encoding of a Unicode string.

See Also:

readUnsignedShort()

writeBoolean

public final void writeBoolean(boolean v)
                        throws java.io.IOException

Writes a boolean to the file as a 1-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0.

Specified by:

writeBoolean in interface java.io.DataOutput

Parameters:

v - a boolean value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeByte

public final void writeByte(int v)
                     throws java.io.IOException

Writes a byte to the file as a 1-byte value.

Specified by:

writeByte in interface java.io.DataOutput

Parameters:

v - a byte value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeShort

public final void writeShort(int v)
                      throws java.io.IOException

Writes a short to the file as two bytes, high byte first.

Specified by:

writeShort in interface java.io.DataOutput

Parameters:

v - a short to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeChar

public final void writeChar(int v)
                     throws java.io.IOException

Writes a char to the file as a 2-byte value, high byte first.

Specified by:

writeChar in interface java.io.DataOutput

Parameters:

v - a char value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeInt

public final void writeInt(int v)
                    throws java.io.IOException

Writes an int to the file as four bytes, high byte first.

Specified by:

writeInt in interface java.io.DataOutput

Parameters:

v - an int to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeLong

public final void writeLong(long v)
                     throws java.io.IOException

Writes a long to the file as eight bytes, high byte first.

Specified by:

writeLong in interface java.io.DataOutput

Parameters:

v - a long to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeFloat

public final void writeFloat(float v)
                      throws java.io.IOException

Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.

Specified by:

writeFloat in interface java.io.DataOutput

Parameters:

v - a float value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

See Also:

Float.floatToIntBits(float)

writeDouble

public final void writeDouble(double v)
                       throws java.io.IOException

Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.

Specified by:

writeDouble in interface java.io.DataOutput

Parameters:

v - a double value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

See Also:

Double.doubleToLongBits(double)

writeBytes

public final void writeBytes(java.lang.String s)
                      throws java.io.IOException

Writes the string to the file as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits.

Specified by:

writeBytes in interface java.io.DataOutput

Parameters:

s - a string of bytes to be written.

Throws:

java.io.IOException - if an I/O error occurs.

writeChars

public final void writeChars(java.lang.String s)
                      throws java.io.IOException

Writes a string to the file as a sequence of characters. Each character is written to the data output stream as if by the writeChar method.

Specified by:

writeChars in interface java.io.DataOutput

Parameters:

s - a String value to be written.

Throws:

java.io.IOException - if an I/O error occurs.

See Also:

writeChar(int)

writeUTF

public final void writeUTF(java.lang.String str)
                    throws java.io.IOException

Writes a string to the file using UTF-8 encoding in a machine-independent manner.

First, two bytes are written to the file as if by the writeShort method giving the number of bytes to follow. This value is the number of bytes actually written out, not the length of the string. Following the length, each character of the string is output, in sequence, using the UTF-8 encoding for each character.

Specified by:

writeUTF in interface java.io.DataOutput

Parameters:

str - a string to be written.

Throws:

java.io.IOException - if an I/O error occurs.