java.lang.Object
- com.mckoi.store.AbstractStore

All Implemented Interfaces:

Store

Direct Known Subclasses:

JournalledFileStore
```
public abstract class AbstractStore
extends java.lang.Object
implements Store
```
Provides an abstract implementation of Store. This implements a bin based best-fit recycling algorithm. The store manages a structure that points to bins of freed space of specific sizes. When an allocation is requested the structure is searched for the first bin that contains an area that best fits the size requested.
Provided the derived class supports safe atomic IO operations, this store is designed for robustness to the level that at no point is the store left in a unworkable (corrupt) state.

Author:

Tobias Downer

Field Summary

Fields
Modifier and Type	Field	Description
`protected static long`	`BIN_AREA_OFFSET`	The offset into the file that the bin area starts.
`protected static int`	`BIN_ENTRIES`
`protected static long`	`DATA_AREA_OFFSET`	The offset into the file that the data areas start.
`protected static long`	`FIXED_AREA_OFFSET`	The offset into the file of the 64 byte fixed area.
`protected long[]`	`free_bin_list`	The free bin list contains 128 entries pointing to the first available block in the bin.
`protected byte[]`	`header_buf`
`protected static int`	`MAGIC`	The magic value.
`protected boolean`	`read_only`	True if this is read-only.
`protected long`	`total_allocated_space`	The total amount of allocated space within this store since the store was openned.
`protected long`	`wilderness_pointer`	A pointer to the wilderness area (the last deleted area in the store), or -1 if there is no wilderness area.

Constructor Summary

Constructors
Modifier Constructor Description

protected AbstractStore(boolean read_only)
Constructs the store.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`checkPointer(long pointer)`	Checks the pointer is valid.
`void`	`close()`	Closes the store.
`protected void`	`coalescArea(long pointer, long size)`	Coalesc one or more areas into a larger area.
`AreaWriter`	`createArea(long size)`	Allocates a block of memory in the store of the specified size and returns an AreaWriter object that can be used to initialize the contents of the area.
`void`	`deleteArea(long id)`	Deletes an area that was previously allocated by the 'createArea' method by the area id.
`protected abstract long`	`endOfDataAreaPointer()`	Returns a pointer to the end of the current data area.
`protected long`	`expandDataArea(long minimum_size)`	Expands the data area by at least the minimum size given.
`java.util.ArrayList`	`findAllocatedAreasNotIn(java.util.ArrayList list)`	Scans the area list, and any areas that aren't deleted and aren't found in the given ArrayList are returned as leaked areas.
`java.util.List`	`getAllAreas()`	Returns a List of Long objects that contain a complete list of all areas in the store.
`Area`	`getArea(long id)`	Returns an object that allows for the contents of an area (represented by the 'id' parameter) to be read.
`protected void`	`getAreaHeader(long pointer, long[] header)`	Sets the 'header' array with information from the header of the given pointer.
`java.io.InputStream`	`getAreaInputStream(long id)`	Returns an InputStream implementation that allows for the area with the given identifier to be read sequentially.
`MutableArea`	`getMutableArea(long id)`	Returns an object that allows for the contents of an area (represented by the 'id' parameter) to be read and written.
`protected long`	`getNextAreaHeader(long pointer, long[] header)`	Sets the 'header' array with information from the next header to the given pointer, and returns a pointer to the next area.
`protected long`	`getPreviousAreaHeader(long pointer, long[] header)`	Sets the 'header' array with information from the previous header to the given pointer, and returns a pointer to the previous area.
`protected abstract void`	`internalClose()`	Internally closes the backing area.
`protected abstract void`	`internalOpen(boolean read_only)`	Internally opens the backing area.
`protected static boolean`	`isValidBoundarySize(long size)`	Returns true if the given area size is valid.
`boolean`	`lastCloseClean()`	Returns true if the store was closed cleanly.
`boolean`	`open()`	Opens the data store.
`void`	`openScanAndFix(UserTerminal terminal)`	Opens/scans the store looking for any errors with the layout.
`protected void`	`readBins()`	Reads the bins from the header information in the file.
`protected abstract int`	`readByteArrayFrom(long position, byte[] buf, int off, int len)`	Reads a byte array from the given position in the file.
`protected abstract int`	`readByteFrom(long position)`	Reads a byte from the given position in the file.
`protected void`	`reboundArea(long pointer, long[] header, boolean write_headers)`	Rebounds the given area with the given header information.
`protected abstract void`	`setDataAreaSize(long length)`	Sets the size of the data area.
`protected void`	`splitArea(long pointer, long new_boundary)`	Splits an area pointed to by 'pointer' at a new boundary point.
`void`	`statsScan(java.util.HashMap properties)`	Performs an extensive lookup on all the tables in this store and sets a number of properties in the given HashMap (property name(String) -> property description(Object)).
`long`	`totalAllocatedSinceStart()`	Returns the total allocated space since the file was openned.
`protected void`	`writeAllBins()`	Updates all bins to the data area header area.
`protected void`	`writeBinIndex(int index)`	Updates the given bin index to the data area header area.
`protected abstract void`	`writeByteArrayTo(long position, byte[] buf, int off, int len)`	Writes a byte array to the given position in the file.
`protected abstract void`	`writeByteTo(long position, int b)`	Writes a byte to the given position in the file.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.mckoi.store.Store
lockForWrite, unlockForWrite

- Field Detail
  - free_bin_list
```
protected long[] free_bin_list
```
    The free bin list contains 128 entries pointing to the first available block in the bin. If the list item contains -1 then there are no free blocks in the bin.
  - wilderness_pointer
```
protected long wilderness_pointer
```
    A pointer to the wilderness area (the last deleted area in the store), or -1 if there is no wilderness area.
  - read_only
```
protected boolean read_only
```
    True if this is read-only.
  - total_allocated_space
```
protected long total_allocated_space
```
    The total amount of allocated space within this store since the store was openned. Note that this could be a negative amount if more space was freed than allocated.
  - DATA_AREA_OFFSET
```
protected static final long DATA_AREA_OFFSET
```
    The offset into the file that the data areas start.
    
    See Also:
    
    Constant Field Values
  - FIXED_AREA_OFFSET
```
protected static final long FIXED_AREA_OFFSET
```
    The offset into the file of the 64 byte fixed area.
    
    See Also:
    
    Constant Field Values
  - BIN_AREA_OFFSET
```
protected static final long BIN_AREA_OFFSET
```
    The offset into the file that the bin area starts.
    
    See Also:
    
    Constant Field Values
  - MAGIC
```
protected static final int MAGIC
```
    The magic value.
    
    See Also:
    
    Constant Field Values
  - header_buf
```
protected final byte[] header_buf
```
  - BIN_ENTRIES
```
protected static final int BIN_ENTRIES
```
- Constructor Detail
  - AbstractStore
```
protected AbstractStore(boolean read_only)
```
    Constructs the store.
- Method Detail
  - open
```
public boolean open()
             throws java.io.IOException
```
    Opens the data store. Returns true if the store did not close cleanly.
    
    Throws:
    
    java.io.IOException
  - close
```
public void close()
           throws java.io.IOException
```
    Closes the store.
    
    Throws:
    
    java.io.IOException
  - isValidBoundarySize
```
protected static boolean isValidBoundarySize(long size)
```
    Returns true if the given area size is valid. Currently the criteria for a valid boundary size is (size >= 24) and (size % 8 == 0) and (size < 200 gigabytes)
  - openScanAndFix
```
public void openScanAndFix(UserTerminal terminal)
                    throws java.io.IOException
```
    Opens/scans the store looking for any errors with the layout. If a problem with the store is detected, it attempts to fix it.
    
    Throws:
    
    java.io.IOException
  - statsScan
```
public void statsScan(java.util.HashMap properties)
               throws java.io.IOException
```
    Performs an extensive lookup on all the tables in this store and sets a number of properties in the given HashMap (property name(String) -> property description(Object)). This should be used for store diagnostics.
    Assume the store is open.
    
    Throws:
    
    java.io.IOException
  - getAllAreas
```
public java.util.List getAllAreas()
                           throws java.io.IOException
```
    Returns a List of Long objects that contain a complete list of all areas in the store. This is useful for checking if a given pointer is valid or not. The returned list is sorted from start area to end area.
    
    Specified by:
    
    getAllAreas in interface Store
    
    Throws:
    
    java.io.IOException
  - findAllocatedAreasNotIn
```
public java.util.ArrayList findAllocatedAreasNotIn(java.util.ArrayList list)
                                            throws java.io.IOException
```
    Scans the area list, and any areas that aren't deleted and aren't found in the given ArrayList are returned as leaked areas. This is a useful method for finding any leaks in the store.
    
    Throws:
    
    java.io.IOException
  - totalAllocatedSinceStart
```
public long totalAllocatedSinceStart()
```
    Returns the total allocated space since the file was openned.
  - internalOpen
```
protected abstract void internalOpen(boolean read_only)
                              throws java.io.IOException
```
    Internally opens the backing area. If 'read_only' is true then the store is openned in read only mode.
    
    Throws:
    
    java.io.IOException
  - internalClose
```
protected abstract void internalClose()
                               throws java.io.IOException
```
    Internally closes the backing area.
    
    Throws:
    
    java.io.IOException
  - readByteFrom
```
protected abstract int readByteFrom(long position)
                             throws java.io.IOException
```
    Reads a byte from the given position in the file.
    
    Throws:
    
    java.io.IOException
  - readByteArrayFrom
```
protected abstract int readByteArrayFrom(long position,
                                         byte[] buf,
                                         int off,
                                         int len)
                                  throws java.io.IOException
```
    Reads a byte array from the given position in the file. Returns the number of bytes read.
    
    Throws:
    
    java.io.IOException
  - writeByteTo
```
protected abstract void writeByteTo(long position,
                                    int b)
                             throws java.io.IOException
```
    Writes a byte to the given position in the file.
    
    Throws:
    
    java.io.IOException
  - writeByteArrayTo
```
protected abstract void writeByteArrayTo(long position,
                                         byte[] buf,
                                         int off,
                                         int len)
                                  throws java.io.IOException
```
    Writes a byte array to the given position in the file.
    
    Throws:
    
    java.io.IOException
  - endOfDataAreaPointer
```
protected abstract long endOfDataAreaPointer()
                                      throws java.io.IOException
```
    Returns a pointer to the end of the current data area.
    
    Throws:
    
    java.io.IOException
  - setDataAreaSize
```
protected abstract void setDataAreaSize(long length)
                                 throws java.io.IOException
```
    Sets the size of the data area.
    
    Throws:
    
    java.io.IOException
  - checkPointer
```
protected void checkPointer(long pointer)
                     throws java.io.IOException
```
    Checks the pointer is valid.
    
    Throws:
    
    java.io.IOException
  - readBins
```
protected void readBins()
                 throws java.io.IOException
```
    Reads the bins from the header information in the file.
    
    Throws:
    
    java.io.IOException
  - writeAllBins
```
protected void writeAllBins()
                     throws java.io.IOException
```
    Updates all bins to the data area header area.
    
    Throws:
    
    java.io.IOException
  - writeBinIndex
```
protected void writeBinIndex(int index)
                      throws java.io.IOException
```
    Updates the given bin index to the data area header area.
    
    Throws:
    
    java.io.IOException
  - getAreaHeader
```
protected void getAreaHeader(long pointer,
                             long[] header)
                      throws java.io.IOException
```
    Sets the 'header' array with information from the header of the given pointer.
    
    Throws:
    
    java.io.IOException
  - getPreviousAreaHeader
```
protected long getPreviousAreaHeader(long pointer,
                                     long[] header)
                              throws java.io.IOException
```
    Sets the 'header' array with information from the previous header to the given pointer, and returns a pointer to the previous area.
    
    Throws:
    
    java.io.IOException
  - getNextAreaHeader
```
protected long getNextAreaHeader(long pointer,
                                 long[] header)
                          throws java.io.IOException
```
    Sets the 'header' array with information from the next header to the given pointer, and returns a pointer to the next area.
    
    Throws:
    
    java.io.IOException
  - reboundArea
```
protected void reboundArea(long pointer,
                           long[] header,
                           boolean write_headers)
                    throws java.io.IOException
```
    Rebounds the given area with the given header information. If 'write_headers' is true, the header (header[0]) is changed. Note that this shouldn't be used to change the size of a chunk.
    
    Throws:
    
    java.io.IOException
  - coalescArea
```
protected void coalescArea(long pointer,
                           long size)
                    throws java.io.IOException
```
    Coalesc one or more areas into a larger area. This alters the boundary of the area to encompass the given size.
    
    Throws:
    
    java.io.IOException
  - expandDataArea
```
protected long expandDataArea(long minimum_size)
                       throws java.io.IOException
```
    Expands the data area by at least the minimum size given. Returns the actual size the data area was expanded by.
    
    Throws:
    
    java.io.IOException
  - splitArea
```
protected void splitArea(long pointer,
                         long new_boundary)
                  throws java.io.IOException
```
    Splits an area pointed to by 'pointer' at a new boundary point.
    
    Throws:
    
    java.io.IOException
  - createArea
```
public AreaWriter createArea(long size)
                      throws java.io.IOException
```
    Description copied from interface: Store
    
    Allocates a block of memory in the store of the specified size and returns an AreaWriter object that can be used to initialize the contents of the area. Note that an area in the store is undefined until the 'finish' method is called in AreaWriter.
    
    Specified by:
    
    createArea in interface Store
    
    Parameters:
    
    size - the amount of memory to allocate.
    
    Returns:
    
    an AreaWriter object that allows the area to be setup.
    
    Throws:
    
    java.io.IOException - if not enough space available to create the area or the store is read-only.
  - deleteArea
```
public void deleteArea(long id)
                throws java.io.IOException
```
    Description copied from interface: Store
    
    Deletes an area that was previously allocated by the 'createArea' method by the area id. Once an area is deleted the resources may be reclaimed. The behaviour of this method is undefined if the id doesn't represent a valid area.
    
    Specified by:
    
    deleteArea in interface Store
    
    Parameters:
    
    id - the identifier of the area to delete.
    
    Throws:
    
    java.io.IOException - (optional) if the id is invalid or the area can not otherwise by deleted.
  - getAreaInputStream
```
public java.io.InputStream getAreaInputStream(long id)
                                       throws java.io.IOException
```
    Description copied from interface: Store
    
    Returns an InputStream implementation that allows for the area with the given identifier to be read sequentially. The behaviour of this method, and InputStream object, is undefined if the id doesn't represent a valid area.
    When 'id' is -1 then a fixed area (64 bytes in size) in the store is returned. The fixed area can be used to store important static static information.
    
    Specified by:
    
    getAreaInputStream in interface Store
    
    Parameters:
    
    id - the identifier of the area to read, or id = -1 is a 64 byte fixed area in the store.
    
    Returns:
    
    an InputStream that allows the area to be read from the start.
    
    Throws:
    
    java.io.IOException - (optional) if the id is invalid or the area can not otherwise be accessed.
  - getArea
```
public Area getArea(long id)
             throws java.io.IOException
```
    Description copied from interface: Store
    
    Returns an object that allows for the contents of an area (represented by the 'id' parameter) to be read. The behaviour of this method, and Area object, is undefined if the id doesn't represent a valid area.
    When 'id' is -1 then a fixed area (64 bytes in size) in the store is returned. The fixed area can be used to store important static static information.
    
    Specified by:
    
    getArea in interface Store
    
    Parameters:
    
    id - the identifier of the area to read, or id = -1 is a 64 byte fixed area in the store.
    
    Returns:
    
    an Area object that allows access to the part of the store.
    
    Throws:
    
    java.io.IOException - (optional) if the id is invalid or the area can not otherwise be accessed.
  - getMutableArea
```
public MutableArea getMutableArea(long id)
                           throws java.io.IOException
```
    Description copied from interface: Store
    
    Returns an object that allows for the contents of an area (represented by the 'id' parameter) to be read and written. The behaviour of this method, and MutableArea object, is undefined if the id doesn't represent a valid area.
    When 'id' is -1 then a fixed area (64 bytes in size) in the store is returned. The fixed area can be used to store important static static information.
    
    Specified by:
    
    getMutableArea in interface Store
    
    Parameters:
    
    id - the identifier of the area to access, or id = -1 is a 64 byte fixed area in the store.
    
    Returns:
    
    a MutableArea object that allows access to the part of the store.
    
    Throws:
    
    java.io.IOException - (optional) if the id is invalid or the area can not otherwise be accessed.
  - lastCloseClean
```
public boolean lastCloseClean()
```
    Description copied from interface: Store
    
    Returns true if the store was closed cleanly. This is important information that may need to be considered when reading information from the store. This is typically used to issue a scan on the data in the store when it is not closed cleanly.
    
    Specified by:
    
    lastCloseClean in interface Store

Class AbstractStore

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface com.mckoi.store.Store

Field Detail

free_bin_list

wilderness_pointer

read_only

total_allocated_space

DATA_AREA_OFFSET

FIXED_AREA_OFFSET

BIN_AREA_OFFSET

MAGIC

header_buf

BIN_ENTRIES

Constructor Detail

AbstractStore

Method Detail

open

close

isValidBoundarySize

openScanAndFix

statsScan

getAllAreas

findAllocatedAreasNotIn

totalAllocatedSinceStart

internalOpen

internalClose

readByteFrom

readByteArrayFrom

writeByteTo

writeByteArrayTo

endOfDataAreaPointer

setDataAreaSize

checkPointer

readBins

writeAllBins

writeBinIndex

getAreaHeader

getPreviousAreaHeader

getNextAreaHeader

reboundArea

coalescArea

expandDataArea

splitArea

createArea

deleteArea

getAreaInputStream

getArea

getMutableArea

lastCloseClean