jetbrains.exodus.io

Interface Block

public interface Block

Block represents single .xd file in Log on storage device - disk, memory, network file system. etc. Block is identified in the log by its address. Block has length in bytes, which is not greater than maximum log block size. Block implementation defines the way data is read from storage device. Log blocks can be mutable and immutable. All blocks having length equal to maximum log block size are immutable. In any moment, only one block can be mutable. This has maximum address.

Since:

1.3.0

See Also:

DataReader, DataWriter, DataReaderWriterProvider, EnvironmentConfig.getLogFileSize()

Method Summary

Modifier and Type	Method and Description
long	getAddress() Returns address of the block in the Log.
long	length() Returns length of the block in bytes.
int	read(byte[] output, long position, int offset, int count) Reads data from the underlying store device.
Block	refresh() For immutable Block implementations, this method returns fresh representation of the same .xd file.

Method Detail

getAddress

long getAddress()

Returns address of the block in the Log. This address is always constant for the block.

Returns:

address of the block in the Log

length

long length()

Returns length of the block in bytes. Block length is always not greater than maximum log file size.

Returns:

length of the block in bytes

See Also:

EnvironmentConfig.getLogFileSize()

read

int read(byte[] output,
         long position,
         int offset,
         int count)

Reads data from the underlying store device.

Parameters:

output - array to copy data

position - starting position in the .xd file

offset - starting offset in the array

count - number of bytes to read

Returns:

actual number of bytes read

refresh

Block refresh()

For immutable Block implementations, this method returns fresh representation of the same .xd file. For mutable Block implementations, this method just returns this Block instance.

Returns:

fresh representation of the same .xd file