Class TKeyArrayPak

class TKeyArrayPak : public TKeyArrayVar;

Description

Defines the characteristics of a key used to access the elements of packed arrays.

An object of this type can represent three categories of key, depending on the constructor used:

1. a descriptor key

2. a text key

3. a numeric key.

The InsertIsqL(), Find() and FindIsqL() member functions of the CArrayPakFlat class hierarchy need a TKeyArrayPak object as an argument to define the location and type of key within an array element.

Note that a TKeyArrayVar object is required for sorting a packed array. The implementation of the SortL() member function of the CArrayPakFlat class constructs a temporary CArrayVarFlat object which requires the TKeyArrayVar object.

Derivation

• TKey - Defines the characteristics of a key used to access the elements of an array.

• TKeyArrayVar - ...

• TKeyArrayPak - ...

Members

Defined in TKeyArrayPak:

• At(TInt)constGets a pointer to the key of a specified array element.
• Set(CBufBase *)
• TKeyArrayPak(TInt,TKeyCmpNumeric)Constructs the characteristics of a numeric key.
• TKeyArrayPak(TInt,TKeyCmpText)Constructs the characteristics of a descriptor key.
• TKeyArrayPak(TInt,TKeyCmpText,TInt)Constructs the characteristics of a text key.

Inherited from TKey:

• Compare(TInt,TInt)constCompares the keys of two array elements.
• SetPtr(const TAny *)Sets the pointer to a sample element whose key is to be used for comparison.
• TKey(TInt,TKeyCmpNumeric)Constructs the characteristics of a numeric key.
• TKey(TInt,TKeyCmpText)Constructs the characteristics of a descriptor type key.
• TKey(TInt,TKeyCmpText,TInt)Constructs the characteristics of a text key.
• iCmpType
• iKeyLength
• iKeyOffset
• iPtr

Inherited from TKeyArrayVar:

• TKeyArrayVar(TInt,TKeyCmpNumeric)Constructs the characteristics of a numeric key.
• TKeyArrayVar(TInt,TKeyCmpText)Constructs the characteristics of a descriptor key.
• TKeyArrayVar(TInt,TKeyCmpText,TInt)Constructs the characteristics of a text key.
• iBase

See also:

• TKeyArrayVar...

IMPORT_C TKeyArrayPak(TInt anOffset, TKeyCmpText aType);

Description

Constructs the characteristics of a descriptor key.

No length value is passed as this is taken from the descriptor type key.

Parameters

TInt anOffset The offset of the key from the start of an array element. TKeyCmpText aType An enumeration which defines the type of comparison to be made between two descriptor keys.

See also:

• TKeyCmpText...

IMPORT_C TKeyArrayPak(TInt anOffset, TKeyCmpText aType, TInt aLength);

Description

Constructs the characteristics of a text key.

Parameters

TInt anOffset The offset of the key from the start of an array element. TKeyCmpText aType An enumeration which defines the type of comparison to be made between two text keys. TInt aLength The length of the text key.

See also:

• TKeyCmpText...

IMPORT_C TKeyArrayPak(TInt anOffset, TKeyCmpNumeric aType);

Description

Constructs the characteristics of a numeric key.

Parameters

TInt anOffset The offset of the key from the start of an array element. TKeyCmpNumeric aType An enumeration which defines the type of the numeric key.

protected: IMPORT_C virtual void Set(CBufBase *aBase);

Description

Parameters

CBufBase *aBase

protected: IMPORT_C virtual TAny* At(TInt anIndex) const;

Description

Gets a pointer to the key of a specified array element.

The default implementation raises a USER 35 panic.

The function is called by TKey::Compare(TInt,TInt)const to compare the keys of two elements.

The implementation provided by a derived class must convert the index to a pointer to the key within the corresponding element. The implementation depends on the design of the array but, as general rule, use the index value to get a pointer to the corresponding element and then add the TKey protected data member iKeyOffset to this pointer to get a pointer to the key itself.

By convention, the index value is relative to zero; i.e. a zero value refers to the first element in the array. By this convention, the index can take any value between zero and the number of elements within the array minus one.

The function must also handle the special index value KIndexPtr. When this value is passed, the function should return a pointer to the key within the sample element. A pointer to the sample element is held in the protected data member iPtr and can be set up using TKey::SetPtr(const TAny *).

The implementation of this function also assumes that the derived class has a pointer to the array itself or has a function for finding it.

Parameters

TInt anIndex The index of the array element or the special index value KIndexPtr.

Return value

TAny * An untyped pointer to the key within the specified array element or an untyped pointer to the key within the sample element, if KIndexPtr is passed as an argument.

Panic codes

USER 35, if no replacement function has been provided by a derived class.

See also:

• TKey::Compare(TInt,TInt)constCompares the keys of two array elements.
• TKey::SetPtr(const TAny *)Sets the pointer to a sample element whose key is to be used for comparison.
• KIndexPtr...