org.magnos.data.store
Class MappedStore

java.lang.Object
  org.magnos.data.store.AbstractStore
      org.magnos.data.store.MappedStore

All Implemented Interfaces:

Store

public class MappedStore
extends AbstractStore

A store which has a memory-mapped file as its persisted medium. All reads and writes are not done immediately, only when the disk is idle or when flush or load are called explicitly. If this store has exclusive or read-write access to the mapped file load does not need to be called before reads.

Author:

Philip Diffenderfer

Constructor Summary

MappedStore(java.io.File file)
Instantiantes a new MappedStore.

MappedStore(java.io.File file, StoreAccess access, int capacity)
Instantiates a new MappedStore while opening it with the given access and setting it the given capacity.

MappedStore(java.lang.String filename)
Instantiantes a new MappedStore.

MappedStore(java.lang.String filename, StoreAccess access, int capacity)
Instantiates a new MappedStore while opening it with the given access and setting it the given capacity.

Method Summary

java.nio.MappedByteBuffer	getBuffer() Returns the memory mapped buffer of the files data.
java.nio.channels.FileChannel	getChannel() Returns the channel used to perform operations on the file.
java.io.File	getFile() Returns the file the store is persisted to.
java.io.RandomAccessFile	getStream() The stream used to perform operations on the file.
protected void	storeClose() Should close the store.
protected void	storeDelete() Deletes the medium to which the store has been persisting to.
protected boolean	storeExists() Returns whether the store exists in its probable medium.
protected void	storeFlush() Should flush the contents of the store from memory to a persisted medium if the implementation supports it.
protected void	storeGet(int location, byte[] bytes, int offset, int length) Gets data at the given location and stores it in the given byte array.
protected void	storeGet(int location, java.nio.ByteBuffer b) Gets data at the given location and stores it in the given ByteBuffer.
protected void	storeLoad() Should load contents of the store into memory from a persisted medium if the implementation supports it.
protected int	storeOpen(StoreAccess access) Should open the store and return the capacity.
protected void	storePut(int location, byte[] bytes, int offset, int length) Puts data at the given location from the given byte array.
protected void	storePut(int location, java.nio.ByteBuffer b) Puts data at the given location from the given ByteBuffer.
protected int	storeResize(int capacity) Resizes the store to the given capacity.

Methods inherited from class org.magnos.data.store.AbstractStore

capacity, capacity, close, create, delete, equals, exists, flush, get, get, get, get, getAccess, getName, hashCode, isAutoFlush, isAutoLoad, isAutoOpen, isClosed, isOpen, load, open, put, put, put, setAccess, setAutoFlush, setAutoLoad, setAutoOpen, toString, validate

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

MappedStore

public MappedStore(java.io.File file,
                   StoreAccess access,
                   int capacity)

Instantiates a new MappedStore while opening it with the given access and setting it the given capacity.

Parameters:

file - The file to persist data to. If this file doesn't exist it will be created when the store is opened, sized, or written to.

access - The requested access to the store.

capacity - The requested capacity of the store.

MappedStore

public MappedStore(java.lang.String filename,
                   StoreAccess access,
                   int capacity)

Instantiates a new MappedStore while opening it with the given access and setting it the given capacity.

Parameters:

filename - The file to persist data to. If this file doesn't exist it will be created when the store is opened, sized, or written to.

access - The requested access to the store.

capacity - The requested capacity of the store.

MappedStore

public MappedStore(java.io.File file)

Instantiantes a new MappedStore.

Parameters:

file - The file to persist data to. If this file doesn't exist it will be created when the store is opened, sized, or written to.

MappedStore

public MappedStore(java.lang.String filename)

Instantiantes a new MappedStore.

Parameters:

filename - The file to persist data to. If this file doesn't exist it will be created when the store is opened, sized, or written to.

Method Detail

getChannel

public java.nio.channels.FileChannel getChannel()

Returns the channel used to perform operations on the file.

Returns:

The stores channel.

getFile

public java.io.File getFile()

Returns the file the store is persisted to.

Returns:

The stores file.

getStream

public java.io.RandomAccessFile getStream()

The stream used to perform operations on the file.

Returns:

The stores data stream.

getBuffer

public java.nio.MappedByteBuffer getBuffer()

Returns the memory mapped buffer of the files data.

Returns:

The stores memory mapped buffer.

storeOpen

protected int storeOpen(StoreAccess access)
                 throws java.io.IOException

Should open the store and return the capacity. If the requested access could not be granted an exception should be thrown. This will only be invoked if the store has been closed previously or has not been opened yet. If the store doesn't exist this should forcefully create it before opening it with the requested access.

Specified by:

storeOpen in class AbstractStore

Returns:

The capacity of the store.

Throws:

java.io.IOException - An error occurred opening the store with the given access.

storeLoad

protected void storeLoad()
                  throws java.io.IOException

Should load contents of the store into memory from a persisted medium if the implementation supports it.

Specified by:

storeLoad in class AbstractStore

Throws:

java.io.IOException - An error occurred loading the store.

storeFlush

protected void storeFlush()
                   throws java.io.IOException

Should flush the contents of the store from memory to a persisted medium if the implementation supports it.

Specified by:

storeFlush in class AbstractStore

Throws:

java.io.IOException - An error occurred flushing the store.

storeClose

protected void storeClose()
                   throws java.io.IOException

Should close the store. This will only be invoked if the store has been successfully opened previously. If there is an error closing the store an exception should be thrown. This exception however may be ignored due to the likeliness that the store is still closed even after an exception is thrown.

Specified by:

storeClose in class AbstractStore

Throws:

java.io.IOException - An error occurred closing the store.

storeDelete

protected void storeDelete()

Deletes the medium to which the store has been persisting to.

Specified by:

storeDelete in class AbstractStore

storeExists

protected boolean storeExists()

Returns whether the store exists in its probable medium. This could be called before or after the store has been opened or created.

Specified by:

storeExists in class AbstractStore

Returns:

True if the store already exists.

storeResize

protected int storeResize(int capacity)
                   throws java.io.IOException

Resizes the store to the given capacity. If the store could not be resized to the requested capacity an exception should be thrown. This will only be called if the store was successfully opened previously. If the resize results in a larger store the end of the store should be padded with zeros (which the system will implicitly due most likely).

Specified by:

storeResize in class AbstractStore

Parameters:

capacity - The new capacity of the store.

Throws:

java.io.IOException - An error occured resizing the store.

storeGet

protected void storeGet(int location,
                        byte[] bytes,
                        int offset,
                        int length)
                 throws java.io.IOException

Gets data at the given location and stores it in the given byte array.

Specified by:

storeGet in class AbstractStore

Parameters:

location - The offset to get the data, in bytes, from the beginning of the store.

bytes - The array of bytes to place the data in.

offset - The offset in the byte array to place the data.

length - The number of bytes to copy from the store and place in the array.

Throws:

java.io.IOException - An error occurred reading from the store.

storePut

protected void storePut(int location,
                        byte[] bytes,
                        int offset,
                        int length)
                 throws java.io.IOException

Puts data at the given location from the given byte array.

Specified by:

storePut in class AbstractStore

Parameters:

location - The offset to put the data, in bytes, from the beginning of the store.

bytes - The array of bytes to take data from.

offset - The offset in the byte array to take the data.

length - The number of bytes to copy from the array and place in the store.

Throws:

java.io.IOException - An error occurred writing to the store.

storeGet

protected void storeGet(int location,
                        java.nio.ByteBuffer b)
                 throws java.io.IOException

Gets data at the given location and stores it in the given ByteBuffer.

Specified by:

storeGet in class AbstractStore

Parameters:

location - The offset to get the data, in bytes, from the beginning of the store.

b - The buffer to place the data in. The buffer will be filled with data to its limit (so it has no remaining bytes).

Throws:

java.io.IOException - An error occurred reading from the store.

storePut

protected void storePut(int location,
                        java.nio.ByteBuffer b)
                 throws java.io.IOException

Puts data at the given location from the given ByteBuffer.

Specified by:

storePut in class AbstractStore

Parameters:

location - The offset to put the data, in bytes, from the beginning of the store.

b - The buffer to take the data from. The buffer will be emptied of data to its limit (so it has no remaining bytes).

Throws:

java.io.IOException - An error occurred writing to the store.