Class TBtree

class TBtree;

Description

Provides ordering of entries by key value in a B+-tree (balanced tree) structure.

Entries and keys are handled as untyped TAny* parameters. You specify an entry in the tree to manipulate through a position (TBtreePos) variable. You can also use iterator functions, which take a TBtreeMark, to move through entries in the tree. The tree's settings can be persisted using a TBtreeToken.

To use this class, you must provide a page pool, based on MPagePool, in which to store entries in the tree, and a key handler, based on MBtreeKey, to provide order and keys.

Members

Defined in TBtree:

• ClearL()Resets the B-tree to have zero-height, and a null root, and deletes all index pa...
• Connect(MPagePool *,const MBtreeKey *,const MBtreeLeafOrg *,const MBtreeIndexOrg *)
• DeleteAtL(TBtreePos &)Deletes the entry at the specified position
• DeleteL(const TAny *)Deletes an entry.
• EEqualToFind the first entry equal to the search target.
• EGreaterEqualFind the first entry greater than or equal to the search target.
• EGreaterThanFind the first entry greater than the search target.
• ELessEqualFind the last entry less than or equal to the search target.
• ELessThanFind the last entry less than the search target.
• ExtractAtL(const TBtreeMark &,TAny *,TInt)constGets an entry at specified iterator position.
• ExtractAtL(const TBtreePos &,TAny *,TInt)constGets the entry at the specified position.
• FindL(TBtreePos &,const TAny *,TFind)constSearches for an entry and returns its position.
• FirstL(TBtreePos &)constGoes to the first entry in the B-tree.
• InsertL(TBtreePos &,const TAny *,TInt,TAllowDuplicates)Inserts an entry into the tree.
• IsBroken()constTests if the broken flag has been set on the B-tree.
• IsDirty()constTests if the dirty flag has been set on the B-tree.
• IsEmpty()constTests if the B-tree is empty.
• IsIntact()constTests if the broken flag has not been set on the B-tree .
• LastL(TBtreePos &)constGoes to the last entry in the B-tree.
• MarkBroken()Sets the broken flag.
• MarkCurrent()Clears the dirty flag.
• MarkDirty()Sets the dirty flag.
• NextL(TBtreeMark &)constAdvances an iterator to the next entry.
• NextL(TBtreePos &)constGets the position of the entry following the specified entry.
• PreviousL(TBtreePos &)constGets the position of the entry preceding the specified entry.
• RepairL()Attempts to repair a broken B-tree.
• ResetL(TBtreeMark &)constResets an iterator to the root of the tree.
• Set(const TBtreeToken &,TBtreeMode)Initialises the B-tree.
• TBtree(TBtreeMode)Constructor that sets the B-tree mode.
• TBtree(const TBtreeToken &,TBtreeMode)Constructor that sets the B-tree mode and initialisation parameters.
• TFindSets the condition for a successful match when calling TBtree::Find().
• Token()constGets an object that encapsulates the TBtree settings.

IMPORT_C TBtree(TBtreeMode aMode);

Description

Constructor that sets the B-tree mode.

Parameters

IMPORT_C TBtree(const TBtreeToken &aToken, TBtreeMode aMode);

Description

Constructor that sets the B-tree mode and initialisation parameters.

Parameters

IMPORT_C void Connect(MPagePool *aPool, const MBtreeKey *aKey, const MBtreeLeafOrg *aLeafOrg, const MBtreeIndexOrg *anIndexOrg);

Description

Parameters

IMPORT_C void Set(const TBtreeToken &aToken, TBtreeMode aMode);

Description

Initialises the B-tree.

Parameters

IMPORT_C TBtreeToken Token() const;

Description

Gets an object that encapsulates the TBtree settings.

That object can then be used to externalise the settings.

Return value

inline TBool IsDirty() const;

Description

Tests if the dirty flag has been set on the B-tree.

Any updates to the B-tree will set this flag on the TBtree object. Applications can use this to determine if they need to flush the page pool and re-save the B-tree token, after which they can call TBtree::MarkCurrent() to indicate that the persistent storage is now up-to-date with the TBtree object.

Return value

inline void MarkCurrent();

Description

Clears the dirty flag.

inline void MarkDirty();

Description

Sets the dirty flag.

inline TBool IsBroken() const;

Description

Tests if the broken flag has been set on the B-tree.

Any updates to the B-tree that fail will leave this flag set on the TBtree object. This indicates that the persistent tree data is broken (corrupt) and the tree needs to be repaired. In this state, none of the functions which use a TBtreePos will work, only those taking a TBtreeMark.

Return value

inline TBool IsIntact() const;

Description

Tests if the broken flag has not been set on the B-tree .

Return value

inline void MarkBroken();

Description

Sets the broken flag.

IMPORT_C TInt RepairL();

Description

Attempts to repair a broken B-tree.

If the operating mode (TBtreeMode) is set to EBtreeSecure, then the tree can be repaired without any loss of data. Otherwise, the tree must be deleted entirely using TBtree::ClearL(), and reconstructed using other means.

Note that if multiple B-trees share a single store page pool, then reclaiming the pool will break all the other B-trees (but the Broken flag will not be set automatically). These trees can be repaired by calling TBtree::MarkBroken() and then TBtree::RepairL(), even if they were not of the EBtreeSecure type.

Return value

inline TBool IsEmpty() const;

Description

Tests if the B-tree is empty.

Return value

IMPORT_C void ClearL();

Description

Resets the B-tree to have zero-height, and a null root, and deletes all index pages.

IMPORT_C TBool FirstL(TBtreePos &aPos) const;

Description

Goes to the first entry in the B-tree.

Parameters

Return value

IMPORT_C TBool LastL(TBtreePos &aPos) const;

Description

Goes to the last entry in the B-tree.

Parameters

Return value

IMPORT_C TBool NextL(TBtreePos &aPos) const;

Description

Gets the position of the entry following the specified entry.

Parameters

Return value

IMPORT_C TBool PreviousL(TBtreePos &aPos) const;

Description

Gets the position of the entry preceding the specified entry.

Parameters

Return value

IMPORT_C TBool FindL(TBtreePos &aPos, const TAny *aKey, TFind aMode=EEqualTo) const;

Description

Searches for an entry and returns its position.

Parameters

Return value

IMPORT_C TBool InsertL(TBtreePos &aPos, const TAny *anEntry, TInt aLength, TAllowDuplicates aDup=ENoDuplicates);

Description

Inserts an entry into the tree.

Parameters

Return value

IMPORT_C TBool DeleteL(const TAny *aKey);

Description

Deletes an entry.

Parameters

Return value

IMPORT_C void DeleteAtL(TBtreePos &aPos);

Description

Deletes the entry at the specified position

Parameters

IMPORT_C void ExtractAtL(const TBtreePos &aPos, TAny *anEntry, TInt aMaxLength) const;

Description

Gets the entry at the specified position.

Parameters

IMPORT_C TBool ResetL(TBtreeMark &aMark) const;

Description

Resets an iterator to the root of the tree.

Parameters

Return value

IMPORT_C TBool NextL(TBtreeMark &aMark) const;

Description

Advances an iterator to the next entry.

Parameters

Return value

IMPORT_C void ExtractAtL(const TBtreeMark &aMark, TAny *anEntry, TInt aMaxLength) const;

Description

Gets an entry at specified iterator position.

Parameters

TFind

Description

Sets the condition for a successful match when calling TBtree::Find().