org.jscsi.target.storage

Interface IStorageModule

All Known Implementing Classes:

RandomAccessStorageModule, SynchronizedRandomAccessStorageModule

public interface IStorageModule

This is an abstract super class offering methods for storage and retrieval of data, as well as emulating some properties of block storage devices.

All index and length parameters used by the read and write methods are referring to bytes, unlike the values sent in CommandDescriptorBlock s.

Author:

Andreas Ergenzinger

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	IStorageModule.STORAGEKIND Enum to denote the modules.

Field Summary

Fields

Modifier and Type	Field and Description
static int	VIRTUAL_BLOCK_SIZE A fictitious block size.

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, int bytesOffset, int length, long storageIndex) Copies bytes from storage to the passed byte array.
void	write(byte[] bytes, int bytesOffset, int length, long storageIndex) Saves part of the passed byte array's content.

Field Detail

VIRTUAL_BLOCK_SIZE

static final int VIRTUAL_BLOCK_SIZE

A fictitious block size.

See Also:

Constant Field Values

Method Detail

checkBounds

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, 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.

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

long getSizeInBlocks()

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

Returns:

the virtual amount of storage blocks available

read

void read(byte[] bytes,
        int bytesOffset,
        int length,
        long storageIndex)
          throws IOException

Copies bytes from storage to the passed byte array.

Parameters:

bytes - the array into which the data will be copied

bytesOffset - the position of the first byte in bytes, which will be filled with data from storage

length - the number of bytes to copy

storageIndex - the position of the first byte to be copied

Throws:

IOException

write

void write(byte[] bytes,
         int bytesOffset,
         int length,
         long storageIndex)
           throws IOException

Saves part of the passed byte array's content.

Parameters:

bytes - the source of the data to be stored

bytesOffset - offset of the first byte to be stored

length - the number of bytes to be copied

storageIndex - byte offset in the storage area

Throws:

IOException

close

void close()
           throws IOException

Closing the storage.

Throws:

IOException - to be closed