org.basex.io
Class DataAccess

java.lang.Object
  org.basex.io.DataAccess

public final class DataAccess
extends java.lang.Object

This class allows positional read access.

Author:

Workgroup DBIS, University of Konstanz 2005-07, ISC License, Christian Gruen

Constructor Summary

DataAccess(java.io.File f)
Constructor, initializing the file reader.

DataAccess(java.lang.String db, java.lang.String fn)
Constructor, initializing the file reader.

Method Summary

void	close() Closes the data access.
void	cursor(long p) Sets the disk cursor.
int	firstID(int p) Returns the first id of an index.
void	flush() Flushes the buffered data.
long	length() Returns file length.
boolean	more() Checks if more bytes can be read.
void	next(int b) Writes the next byte.
long	pos() Returns the input position.
int	read() Reads the next byte.
int	read4(long p) Reads an integer value from the specified position.
long	read5(long p) Reads a five-byte value from the specified position.
byte[]	readBytes(long p) Reads a text from disk.
byte[]	readBytes(long from, long to) Reads a number of bytes in range from -> to and returns them as array.
int	readInt(long p) Reads an integer value from the specified position.
int[]	readInts(long from, long to) Reads a number of int values in range from -> to and returns them as array.
int	readNum(long p) Reads a Num value from disk.
void	writeBytes(byte[] v) Append a value to the file and return it's offset.

Methods inherited from class java.lang.Object

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

Constructor Detail

DataAccess

public DataAccess(java.io.File f)
           throws java.io.IOException

Constructor, initializing the file reader.

Parameters:

f - the file to be read

Throws:

java.io.IOException - IO Exception

DataAccess

public DataAccess(java.lang.String db,
                  java.lang.String fn)
           throws java.io.IOException

Constructor, initializing the file reader.

Parameters:

db - name of the database

fn - the file to be read

Throws:

java.io.IOException - IO Exception

Method Detail

close

public void close()
           throws java.io.IOException

Closes the data access.

Throws:

java.io.IOException - in case of write errors

cursor

public void cursor(long p)

Sets the disk cursor.

Parameters:

p - read position

firstID

public int firstID(int p)

Returns the first id of an index.

Parameters:

p - position

Returns:

id

flush

public void flush()

Flushes the buffered data.

length

public long length()

Returns file length.

Returns:

file length

more

public boolean more()

Checks if more bytes can be read.

Returns:

result of check

next

public void next(int b)

Writes the next byte.

Parameters:

b - byte to be written

pos

public long pos()

Returns the input position.

Returns:

position

read

public int read()

Reads the next byte.

Returns:

next byte

read4

public int read4(long p)

Reads an integer value from the specified position.

Parameters:

p - position

Returns:

integer value

read5

public long read5(long p)

Reads a five-byte value from the specified position.

Parameters:

p - position

Returns:

integer value

readBytes

public byte[] readBytes(long p)

Reads a text from disk.

Parameters:

p - text position

Returns:

text as byte array

readBytes

public byte[] readBytes(long from,
                        long to)

Reads a number of bytes in range from -> to and returns them as array.

Parameters:

from - starting position for reading

to - ending position for reading

Returns:

byte array

readInt

public int readInt(long p)

Reads an integer value from the specified position.

Parameters:

p - position

Returns:

integer value

readInts

public int[] readInts(long from,
                      long to)

Reads a number of int values in range from -> to and returns them as array.

Parameters:

from - starting position for reading

to - ending position for reading

Returns:

int array

readNum

public int readNum(long p)

Reads a Num value from disk.

Parameters:

p - text position

Returns:

read num

writeBytes

public void writeBytes(byte[] v)

Append a value to the file and return it's offset. MAY but currently doesn't return an existing index, given the value is the same.

Parameters:

v - byte array to be appended