com.sun.xfile

Class XRandomAccessFile

Implemented Interfaces:
DataInput, DataOutput

public class XRandomAccessFile
extends java.lang.Object
implements DataOutput, 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(String name, String mode)
Creates a random access file to read from, and optionally to write to, a file with the specified name.
XRandomAccessFile(XFile xf, 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(b[] )
Reads up to b.length bytes of data from this file into an array of bytes.
int
read(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(b[] )
Reads b.length bytes from this file into the byte array.
void
readFully(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.
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.
String
readUTF()
Reads in a string 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.
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(b[] )
Writes b.length bytes from the specified byte array starting at offset off to this file.
void
write(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(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(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(String str)
Writes a string to the file using UTF-8 encoding in a machine-independent manner.

Constructor Details

XRandomAccessFile

public XRandomAccessFile(String name,
                         String mode)
            throws 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.

XRandomAccessFile

public XRandomAccessFile(XFile xf,
                         String mode)
            throws 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.

Method Details

close

public void close()
            throws 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.

flush

public void flush()
            throws IOException
Forces any buffered output bytes to be written out.

getFilePointer

public long getFilePointer()
            throws 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.

length

public long length()
            throws IOException
Returns the length of this file.
Returns:
the length of this file.

read

public int read()
            throws 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.

read

public int read(b[] )
            throws IOException
Reads up to b.length bytes of data from this file into an array of bytes.
Parameters:
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.

read

public int read(b[] ,
                int off,
                int len)
            throws IOException
Reads up to len bytes of data from this file into an array of bytes.
Parameters:
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.

readBoolean

public final boolean readBoolean()
            throws 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.
Returns:
the boolean value read.

readByte

public final byte readByte()
            throws 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.

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

readChar

public final char readChar()
            throws 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.

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

readDouble

public final double readDouble()
            throws 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.

Returns:
the next eight bytes of this file, interpreted as a double.
See Also:
readLong(), java.lang.Double.longBitsToDouble(long)

readFloat

public final float readFloat()
            throws 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.

Returns:
the next four bytes of this file, interpreted as a float.
See Also:
readInt(), java.lang.Float.intBitsToFloat(int)

readFully

public final void readFully(b[] )
            throws IOException
Reads b.length bytes from this file into the byte array.
Parameters:

readFully

public final void readFully(b[] ,
                            int off,
                            int len)
            throws IOException
Reads exactly len bytes from this file into the byte array.
Parameters:
off - the start offset of the data.
len - the number of bytes to read.

readInt

public final int readInt()
            throws 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.

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

readLine

public final String readLine()
            throws 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.

Returns:
the next line of text from this file.

readLong

public final long readLong()
            throws 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.

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

readShort

public final short readShort()
            throws 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.

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

readUTF

public final String readUTF()
            throws 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.

Returns:
a Unicode string.

readUnsignedByte

public final int readUnsignedByte()
            throws 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.

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

readUnsignedShort

public final int readUnsignedShort()
            throws 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.

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

seek

public void seek(long pos)
            throws IOException
Sets the offset from the beginning of this file at which the next read or write occurs.
Parameters:
pos - the absolute position.

skipBytes

public int skipBytes(int n)
            throws IOException
Skips exactly n bytes of input.

Parameters:
n - the number of bytes to be skipped.
Returns:
the number of bytes skipped, which is always n.

write

public void write(b[] )
            throws IOException
Writes b.length bytes from the specified byte array starting at offset off to this file.
Parameters:

write

public void write(b[] ,
                  int off,
                  int len)
            throws IOException
Writes len bytes from the specified byte array starting at offset off to this file.
Parameters:
off - the start offset in the data.
len - the number of bytes to write.

write

public void write(int b)
            throws IOException
Writes the specified byte to this file.
Parameters:
b - the byte to be written.

writeBoolean

public final void writeBoolean(boolean v)
            throws 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.
Parameters:
v - a boolean value to be written.

writeByte

public final void writeByte(int v)
            throws IOException
Writes a byte to the file as a 1-byte value.
Parameters:
v - a byte value to be written.

writeBytes

public final void writeBytes(String s)
            throws 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.
Parameters:
s - a string of bytes to be written.

writeChar

public final void writeChar(int v)
            throws IOException
Writes a char to the file as a 2-byte value, high byte first.
Parameters:
v - a char value to be written.

writeChars

public final void writeChars(String s)
            throws 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.
Parameters:
s - a String value to be written.

writeDouble

public final void writeDouble(double v)
            throws 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.
Parameters:
v - a double value to be written.
See Also:
java.lang.Double.doubleToLongBits(double)

writeFloat

public final void writeFloat(float v)
            throws 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.
Parameters:
v - a float value to be written.
See Also:
java.lang.Float.floatToIntBits(float)

writeInt

public final void writeInt(int v)
            throws IOException
Writes an int to the file as four bytes, high byte first.
Parameters:
v - an int to be written.

writeLong

public final void writeLong(long v)
            throws IOException
Writes a long to the file as eight bytes, high byte first.
Parameters:
v - a long to be written.

writeShort

public final void writeShort(int v)
            throws IOException
Writes a short to the file as two bytes, high byte first.
Parameters:
v - a short to be written.

writeUTF

public final void writeUTF(String str)
            throws 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.

Parameters:
str - a string to be written.