Class VirtualRandomAccessFile

java.lang.Object

org.apache.derby.impl.io.vfmem.VirtualRandomAccessFile

All Implemented Interfaces:

DataInput, DataOutput, StorageRandomAccessFile

public class VirtualRandomAccessFile
extends Object
implements StorageRandomAccessFile

A random access file capable of reading and writing from/into a virtual file whose data is represented by a BlockedByteArray.

If the file is opened in read-only mode and the caller invokes one of the write methods, it will fail with a NullPointerException.

Field Summary

Fields

Modifier and Type	Field	Description
private final boolean	_readOnly	whether the file is read-only
private final BlockedByteArrayInputStream	bIn	Stream used to read from the source entry.
private final BlockedByteArrayOutputStream	bOut	Stream used to write into the source entry.
private final DataInputStream	dIs	Data input stream on top of the source input stream.
private final DataOutputStream	dOs	Data output stream on top of the source output stream.
private final DataStoreEntry	entry	The source entry.
private long	fp	Current position / file pointer.

Constructor Summary

Constructors

Constructor	Description
VirtualRandomAccessFile(DataStoreEntry entry, boolean readOnly)	Creates a new virtual random access file.

Method Summary

Modifier and Type	Method	Description
VirtualRandomAccessFile	clone()	Clone this file abstraction
void	close()	Closes this file.
long	getFilePointer()	Get the current offset in this file.
long	length()	Gets the length of this file.
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()
byte	readByte()
char	readChar()
double	readDouble()
float	readFloat()
void	readFully(byte[] b)
void	readFully(byte[] b, int off, int len)
int	readInt()
String	readLine()
long	readLong()
short	readShort()
int	readUnsignedByte()
int	readUnsignedShort()
String	readUTF()
void	seek(long newFilePointer)	Set the file pointer.
void	setLength(long newLength)	Sets the length of this file, either extending or truncating it.
int	skipBytes(int n)
void	sync()	Force any changes out to the persistent store.
void	write(byte[] b)
void	write(byte[] b, int off, int len)
void	write(int b)
void	writeBoolean(boolean v)
void	writeByte(int v)
void	writeBytes(String s)
void	writeChar(int v)
void	writeChars(String s)
void	writeDouble(double v)
void	writeFloat(float v)
void	writeInt(int v)
void	writeLong(long v)
void	writeShort(int v)
void	writeUTF(String s)

Methods inherited from class Object

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

Field Details

entry

private final DataStoreEntry entry

The source entry.

_readOnly

private final boolean _readOnly

whether the file is read-only

fp

private long fp

Current position / file pointer.

bIn

private final BlockedByteArrayInputStream bIn

Stream used to read from the source entry.

dIs

private final DataInputStream dIs

Data input stream on top of the source input stream.

bOut

private final BlockedByteArrayOutputStream bOut

Stream used to write into the source entry. Will be null if the file is opened in read-only mode.

dOs

private final DataOutputStream dOs

Data output stream on top of the source output stream. Will be null if the file is opened in read-only mode.

Constructor Details

VirtualRandomAccessFile

public VirtualRandomAccessFile(DataStoreEntry entry,
 boolean readOnly)
                        throws FileNotFoundException

Creates a new virtual random access file.

Parameters:

entry - the source entry

readOnly - if the file should be opened read-only or not

Throws:

FileNotFoundException - if the denoted path is a directory, or the denoted file has been marked read-only and the file is opened for writing

Method Details

clone

public VirtualRandomAccessFile clone()

Description copied from interface: StorageRandomAccessFile

Clone this file abstraction

Specified by:

clone in interface StorageRandomAccessFile

Overrides:

clone in class Object

close

public void close()
           throws IOException

Description copied from interface: StorageRandomAccessFile

Closes this file.

Specified by:

close in interface StorageRandomAccessFile

Throws:

IOException - - if an I/O error occurs.

getFilePointer

public long getFilePointer()

Description copied from interface: StorageRandomAccessFile

Get the current offset in this file.

Specified by:

getFilePointer in interface StorageRandomAccessFile

Returns:

the current file pointer.

length

public long length()

Description copied from interface: StorageRandomAccessFile

Gets the length of this file.

Specified by:

length in interface StorageRandomAccessFile

Returns:

the number of bytes this file.

seek

public void seek(long newFilePointer)
          throws IOException

Description copied from interface: StorageRandomAccessFile

Set the file pointer. It may be moved beyond the end of the file, but this does not change the length of the file. The length of the file is not changed until data is actually written..

Specified by:

seek in interface StorageRandomAccessFile

Parameters:

newFilePointer - the new file pointer, measured in bytes from the beginning of the file.

Throws:

IOException - - if newFilePointer is less than 0 or an I/O error occurs.

setLength

public void setLength(long newLength)

Description copied from interface: StorageRandomAccessFile

Sets the length of this file, either extending or truncating it.

If the file is extended then the contents of the extension are not defined.

If the file is truncated and the file pointer is greater than the new length then the file pointer is set to the new length.

Specified by:

setLength in interface StorageRandomAccessFile

Parameters:

newLength - The new file length.

sync

public void sync()

Description copied from interface: StorageRandomAccessFile

Force any changes out to the persistent store. If the database is to be transient, that is, if the database does not survive a restart, then the sync method implementation need not do anything.

Specified by:

sync in interface StorageRandomAccessFile

read

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

Description copied from interface: StorageRandomAccessFile

Reads up to len bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

Specified by:

read in interface StorageRandomAccessFile

Parameters:

b - the buffer into which the data is read.

off - the start offset in array b at which the data is written.

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:

IOException - If the first byte cannot be read for any reason other than end of file, or if the random access file has been closed, or if some other I/O error occurs.

readFully

public void readFully(byte[] b)
               throws IOException

Specified by:

readFully in interface DataInput

Throws:

IOException

readFully

public void readFully(byte[] b,
 int off,
 int len)
               throws IOException

Specified by:

readFully in interface DataInput

Throws:

IOException

skipBytes

public int skipBytes(int n)

Specified by:

skipBytes in interface DataInput

readBoolean

public boolean readBoolean()
                    throws IOException

Specified by:

readBoolean in interface DataInput

Throws:

IOException

readByte

public byte readByte()
              throws IOException

Specified by:

readByte in interface DataInput

Throws:

IOException

readUnsignedByte

public int readUnsignedByte()
                     throws IOException

Specified by:

readUnsignedByte in interface DataInput

Throws:

IOException

readShort

public short readShort()
                throws IOException

Specified by:

readShort in interface DataInput

Throws:

IOException

readUnsignedShort

public int readUnsignedShort()
                      throws IOException

Specified by:

readUnsignedShort in interface DataInput

Throws:

IOException

readChar

public char readChar()
              throws IOException

Specified by:

readChar in interface DataInput

Throws:

IOException

readInt

public int readInt()
            throws IOException

Specified by:

readInt in interface DataInput

Throws:

IOException

readLong

public long readLong()
              throws IOException

Specified by:

readLong in interface DataInput

Throws:

IOException

readFloat

public float readFloat()
                throws IOException

Specified by:

readFloat in interface DataInput

Throws:

IOException

readDouble

public double readDouble()
                  throws IOException

Specified by:

readDouble in interface DataInput

Throws:

IOException

readLine

public String readLine()
                throws IOException

Specified by:

readLine in interface DataInput

Throws:

IOException

readUTF

public String readUTF()
               throws IOException

Specified by:

readUTF in interface DataInput

Throws:

IOException

write

public void write(int b)
           throws IOException

Specified by:

write in interface DataOutput

Throws:

IOException

write

public void write(byte[] b)
           throws IOException

Specified by:

write in interface DataOutput

Throws:

IOException

write

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

Specified by:

write in interface DataOutput

Throws:

IOException

writeBoolean

public void writeBoolean(boolean v)
                  throws IOException

Specified by:

writeBoolean in interface DataOutput

Throws:

IOException

writeByte

public void writeByte(int v)
               throws IOException

Specified by:

writeByte in interface DataOutput

Throws:

IOException

writeShort

public void writeShort(int v)
                throws IOException

Specified by:

writeShort in interface DataOutput

Throws:

IOException

writeChar

public void writeChar(int v)
               throws IOException

Specified by:

writeChar in interface DataOutput

Throws:

IOException

writeInt

public void writeInt(int v)
              throws IOException

Specified by:

writeInt in interface DataOutput

Throws:

IOException

writeLong

public void writeLong(long v)
               throws IOException

Specified by:

writeLong in interface DataOutput

Throws:

IOException

writeFloat

public void writeFloat(float v)
                throws IOException

Specified by:

writeFloat in interface DataOutput

Throws:

IOException

writeDouble

public void writeDouble(double v)
                 throws IOException

Specified by:

writeDouble in interface DataOutput

Throws:

IOException

writeBytes

public void writeBytes(String s)
                throws IOException

Specified by:

writeBytes in interface DataOutput

Throws:

IOException

writeChars

public void writeChars(String s)
                throws IOException

Specified by:

writeChars in interface DataOutput

Throws:

IOException

writeUTF

public void writeUTF(String s)
              throws IOException

Specified by:

writeUTF in interface DataOutput

Throws:

IOException