| com.mckoi.store.Store
All known Subclasses: com.mckoi.store.HeapStore, com.mckoi.store.AbstractStore,
| Store | | public interface Store (Code) | | A store is a resource where areas can be allocated and freed to store
objects. A store can be backed by a file or main memory, or a combination of
the two.
Some characteristics of implementations of Store may be separately
specified. For example, a file based store that is intended to persistently
store objects may have robustness as a primary requirement. A main memory
based store, or other type of volatile store, may not require robustness.
author:
Tobias Downer |
| Method Summary | |
| 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. | | List | getAllAreas()
Returns a complete list of pointers to all areas in the Store as Long
objects sorted from lowest pointer to highest. | | Area | getArea(long id)
Returns an object that allows for the contents of an area (represented by
the 'id' parameter) to be read. | | 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. | | boolean | lastCloseClean()
Returns true if the store was closed cleanly. | | void | lockForWrite()
It is often useful to guarentee that a certain sequence of updates to a
store is completed and not broken in the middle. | | void | unlockForWrite()
See the 'lockForWrite' method description. |
| createArea | | AreaWriter createArea(long size) throws IOException(Code) | | 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.
Parameters:
size - the amount of memory to allocate. an AreaWriter object that allows the area to be setup.
throws:
IOException - if not enough space available to create the area orthe store is read-only. |
| deleteArea | | void deleteArea(long id) throws IOException(Code) | | 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.
Parameters:
id - the identifier of the area to delete.
throws:
IOException - (optional) if the id is invalid or the area can nototherwise by deleted. |
| getAllAreas | | List getAllAreas() throws IOException(Code) | | Returns a complete list of pointers to all areas in the Store as Long
objects sorted from lowest pointer to highest. This should be used for
diagnostics only because it may be difficult for this to be generated
with some implementations. It is useful in a repair tool to determine if
a pointer is valid or not.
|
| getArea | | Area getArea(long id) throws IOException(Code) | | 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.
Parameters:
id - the identifier of the area to read, or id = -1 is a 64 bytefixed area in the store. an Area object that allows access to the part of the store.
throws:
IOException - (optional) if the id is invalid or the area can nototherwise be accessed. |
| getAreaInputStream | | InputStream getAreaInputStream(long id) throws IOException(Code) | | 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.
Parameters:
id - the identifier of the area to read, or id = -1 is a 64 bytefixed area in the store. an InputStream that allows the area to be read from the start.
throws:
IOException - (optional) if the id is invalid or the area can nototherwise be accessed. |
| getMutableArea | | MutableArea getMutableArea(long id) throws IOException(Code) | | 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.
Parameters:
id - the identifier of the area to access, or id = -1 is a 64 bytefixed area in the store. a MutableArea object that allows access to the part of the store.
throws:
IOException - (optional) if the id is invalid or the area can nototherwise be accessed. |
| lastCloseClean | | boolean lastCloseClean()(Code) | | 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.
|
| lockForWrite | | void lockForWrite()(Code) | | It is often useful to guarentee that a certain sequence of updates to a
store is completed and not broken in the middle. For example, when
inserting data into a table you don't want a record to be partially
written when a check point is made. You want the entire sequence of
modifications to be completed before the check point can run. This
means that if a crash occurs, a check point will not recover to a
possible corrupt file.
To achieve this, the 'lockForWrite' and 'unlockForWrite' methods are
available. When 'lockForWrite' has been called, a check point can not
created until there are no write locks obtained on the table.
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| unlockForWrite | | void unlockForWrite()(Code) | | See the 'lockForWrite' method description.
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