Package com.mckoi.store

Interface StoreDataAccessor

All Known Implementing Classes:

IOStoreDataAccessor, ScatteringStoreDataAccessor

interface StoreDataAccessor

An interface for low level store data access methods. This is used to implement a variety of ways of accessing data from some resource, such as a file in a filesystem. For example, we might use this to access a file using the NIO API, or through the IO API. Alternatively we may use it to implement a scattering store that includes data across multiple files in the filesystem.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the underlying data area representation.
boolean	delete()	Deletes the data area resource.
boolean	exists()	Returns true if the resource exists.
long	getSize()	Returns the current size of the underlying data area.
void	open(boolean read_only)	Opens the underlying data area representation.
void	read(long position, byte[] buf, int off, int len)	Reads a block of data from the underlying data area at the given position into the byte array at the given offset.
void	setSize(long new_size)	Sets the size of the underlying data area to the given size.
void	synch()	Synchronizes the data area by forcing any data out of the OS buffers onto the disk.
void	write(long position, byte[] buf, int off, int len)	Writes a block of data to the underlying data area from the byte array at the given offset.

Method Detail

exists

boolean exists()

Returns true if the resource exists.

delete

boolean delete()

Deletes the data area resource. Returns true if the delete was successful.

open

void open(boolean read_only)
   throws java.io.IOException

Opens the underlying data area representation. If the resource doesn't exist then it is created and the size is set to 0.

Throws:

java.io.IOException

close

void close()
    throws java.io.IOException

Closes the underlying data area representation.

Throws:

java.io.IOException

read

void read(long position,
          byte[] buf,
          int off,
          int len)
   throws java.io.IOException

Reads a block of data from the underlying data area at the given position into the byte array at the given offset.

Throws:

java.io.IOException

write

void write(long position,
           byte[] buf,
           int off,
           int len)
    throws java.io.IOException

Writes a block of data to the underlying data area from the byte array at the given offset.

Throws:

java.io.IOException

setSize

void setSize(long new_size)
      throws java.io.IOException

Sets the size of the underlying data area to the given size. If the size of the data area is increased, the content between the old size and the new size is implementation defined.

Throws:

java.io.IOException

getSize

long getSize()
      throws java.io.IOException

Returns the current size of the underlying data area.

Throws:

java.io.IOException

synch

void synch()
    throws java.io.IOException

Synchronizes the data area by forcing any data out of the OS buffers onto the disk.

Throws:

java.io.IOException