Class RStorePagePool

RStorePagePool

Support

Supported from 5.0

Description

Uses a store to implement the page pool interface MPagePool.

Pages can be reclaimable (tracked by the page pool, so that they can be freed when required) or not (in which case they must be deleted explicitly): this is indicated by a flag of type TPageReclamation. Non-reclaimable pages each have their own stream in the store; reclaimable pages are bundled 15 to a stream. To track the reclaimable pages, the page pool has a separate token, type TStorePagePoolToken, that must be saved by the user of the pool.

The store used must support CStreamStore::ExtendL(), CStreamStore::DeleteL() and allow streams to be re-written. CPermanentFileStore meets these conditions.

A store page pool uses a cache to store pages in-memory and to cache frequently accessed pages. You should provide a cache object (CPageCache) to the pool for this purpose.

Derivation

MPagePool Interface to a page pool, the storage abstraction used by the B-trees API RStorePagePool Uses a store to implement the page pool interface MPagePool TCachePagePool Provides a page pool with cached pages

Defined in RStorePagePool:
Close(), Create(), Discard(), HasAvailable(), IsDirty(), IsEmpty(), MarkCurrent(), MarkDirty(), Open(), RStorePagePool(), ReclaimAllL(), ReclaimL(), Release(), Token()

Inherited from MPagePool:
Delete(), DeleteL(), Pop(), PushL()

Inherited from TCachePagePool:
AcquireL(), AllocL(), AssignL(), Flush(), FlushL(), LockL(), Purge(), Set(), Unlock(), UpdateL()

See also:

• CPageCache
• CPermanentFileStore
• CStreamStore
• TPageReclamation

RStorePagePool();

Description

Default constructor.

RStorePagePool(CPageCache& aCache);

Description

Constructor with a page cache for the pool.

Parameters

CPageCache& aCache Page cache for the pool

RStorePagePool(CStreamStore& aStore);

Description

Constructor with a stream store to use for the pool.

Parameters

CStreamStore& aStore Stream store to use for the pool

RStorePagePool(CStreamStore& aStore,const TStorePagePoolToken& aToken);

Description

Constructor with a stream store and settings to use for the pool.

Parameters

CStreamStore& aStore Stream store to use for the pool const TStorePagePoolToken& aToken Stream store pool settings

void Create(CStreamStore& aStore);

Description

Creates a new pool.

Parameters

CStreamStore& aStore Stream store to use for the pool

void Open(CStreamStore& aStore,const TStorePagePoolToken& aToken);

Description

Opens an existing pool.

Parameters

CStreamStore& aStore Stream store for the pool const TStorePagePoolToken& aToken Pool settings

void Close();

Description

Flushes and purges the page cache and stops using the stream store.

TBool ReclaimL();

Description

Deletes the first stream that stores reclaimable pages in the store.

Return value

TBool True if there are remaining streams (pages), false if there are no more streams

void ReclaimAllL();

Description

Deletes all streams in the store.

void Release();

Description

Purges the page cache and stops using the stream store.

void Discard();

Description

Invalidates the list of free pages in the reclaimable set.

This should be done if there has been a failure in updating the BTree, as this list is possibly corrupt now. The reclaimable set can be deleted using ReclaimAllL(), and the BTree then repaired.

TBool HasAvailable() const;

Description

Tests if there is a free page in the pool.

Return value

TBool True if there is a free page in the pool, otherwise false

TBool IsDirty() const;

Description

Tests if the dirty flag has been set on the page pool.

Return value

TBool True if the dirty flag has been set, otherwise false

TBool IsEmpty() const;

Description

Tests if the page pool is empty.

Return value

TBool True if the page pool is empty, otherwise false

void MarkCurrent();

Description

Clears the dirty flag.

void MarkDirty();

Description

Sets the dirty flag on the pool.

TStorePagePoolToken Token() const;

Description

Gets an object that encapsulates the page pool settings.

That object can then be used to externalise the settings.

Return value

TStorePagePoolToken Encapsulates the page pool settings