org.jscsi.target.storage

Class JCloudsStorageModule

java.lang.Object

org.jscsi.target.storage.JCloudsStorageModule

All Implemented Interfaces:

IStorageModule

@Beta
public class JCloudsStorageModule
extends Object
implements IStorageModule

JClouds-Binding to store blocks as buckets in clouds-backends. This class utilizes caching as well as multithreaded writing to improve performance.

Author:

Sebastian Graf, University of Konstanz

Field Summary

Fields

Modifier and Type	Field and Description
static int	BLOCK_IN_CLUSTER Number of Blocks in one Cluster.
static String	CONTAINERNAME
static int	SIZE_PER_BUCKET Number of Bytes in Bucket.

Fields inherited from interface org.jscsi.target.storage.IStorageModule

VIRTUAL_BLOCK_SIZE

Constructor Summary

Constructors

Constructor and Description
JCloudsStorageModule(long pSizeInBlocks, File pFile) Creates a new JCloudsStorageModule backed by the specified file.

Method Summary

Methods

Modifier and Type	Method and Description
int	checkBounds(long logicalBlockAddress, int transferLengthInBlocks) This method can be used for checking if a (series of) I/O operations will result in an IOException due to trying to access blocks outside the medium's boundaries.
void	close() Closing the storage.
long	getSizeInBlocks() Returns the storage space size in bytes divided by the block size in bytes (rounded down).
void	read(byte[] bytes, long storageIndex) Copies bytes from storage to the passed byte array.
void	write(byte[] bytes, long storageIndex) Saves part of the passed byte array's content.

Methods inherited from class java.lang.Object

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

Field Detail

BLOCK_IN_CLUSTER

public static final int BLOCK_IN_CLUSTER

Number of Blocks in one Cluster.

See Also:

Constant Field Values

SIZE_PER_BUCKET

public static final int SIZE_PER_BUCKET

Number of Bytes in Bucket.

See Also:

Constant Field Values

CONTAINERNAME

public static final String CONTAINERNAME

See Also:

Constant Field Values

Constructor Detail

JCloudsStorageModule

public JCloudsStorageModule(long pSizeInBlocks,
                    File pFile)

Creates a new JCloudsStorageModule backed by the specified file. If no such file exists, a FileNotFoundException will be thrown.

Parameters:

pSizeInBlocks - blocksize for this module

pFile - local storage, not used over here

Method Detail

checkBounds

public int checkBounds(long logicalBlockAddress,
              int transferLengthInBlocks)

This method can be used for checking if a (series of) I/O operations will result in an IOException due to trying to access blocks outside the medium's boundaries.

The SCSI standard requires checking for these boundary violations right after receiving a read or write command, so that an appropriate error message can be returned to the initiator. Therefore this method must be called prior to each read or write sequence.

The values returned by this method and their meaning with regard to the interval [0, IStorageModule.getSizeInBlocks() - 1] are shown in the following table:

Return Value	Meaning
0	no boundaries are violated
1	the logicalBlockAddress parameter lies outside of the interval
2	the interval [logicalBlockAddress, logicalBlockAddress + transferLengthInBlocks] lies outside of the interval, or transferLengthInBlocks is negative

Note that the parameters of this method are referring to blocks, not to byte indices.

Specified by:

checkBounds in interface IStorageModule

Parameters:

logicalBlockAddress - the index of the first block of data to be read or written

transferLengthInBlocks - the total number of consecutive blocks about to be read or written

Returns:

see table in description

getSizeInBlocks

public long getSizeInBlocks()

Returns the storage space size in bytes divided by the block size in bytes (rounded down).

Specified by:

getSizeInBlocks in interface IStorageModule

Returns:

the virtual amount of storage blocks available

read

public void read(byte[] bytes,
        long storageIndex)
          throws IOException

Copies bytes from storage to the passed byte array.

Specified by:

read in interface IStorageModule

Parameters:

bytes - the array into which the data will be copied will be filled with data from storage

storageIndex - the position of the first byte to be copied

Throws:

IOException

write

public void write(byte[] bytes,
         long storageIndex)
           throws IOException

Saves part of the passed byte array's content.

Specified by:

write in interface IStorageModule

Parameters:

bytes - the source of the data to be stored

storageIndex - byte offset in the storage area

Throws:

Exception

IOException

close

public void close()
           throws IOException

Closing the storage.

Specified by:

close in interface IStorageModule

Throws:

IOException - to be closed