Class TDesC8

TDesC8

Support

Supported from 5.0

Description

Abstract base class for 8 bit non-modifiable descriptors.

The class encapsulates the data member containing the length of data represented by an 8 bit descriptor. It also provides member functions through which the data can be accessed but not modified.

Data represented by this class is treated as a contiguous set of 8-bit (i.e. single byte) values or data items.

This class cannot be instantiated as it is intended to form part of a class hierarchy; it provides a well defined part of descriptor behaviour. It can, however, be passed as an argument type for functions which want access to descriptor data but do not need to modify that data.

Defined in TDesC8:
Alloc(), AllocL(), AllocLC(), Compare(), CompareC(), CompareF(), Find(), FindC(), FindF(), Left(), Length(), Locate(), LocateF(), LocateReverse(), LocateReverseF(), Match(), MatchC(), MatchF(), Mid(), Ptr(), Right(), Size(), operator!=(), operator<(), operator<=(), operator==(), operator>(), operator>=(), operator[]()

See also:

• TPtrC8

TInt Length() const;

Description

Gets the length of the data. This is the number of 8 bit values or data items represented by the descriptor.

Return value

TInt The length of the data represented by the descriptor.

TInt Size() const;

Description

Gets the size of the data. This is the number of bytes occupied by the data represented by the descriptor.

Return value

TInt The size of the data represented by the descriptor.

const TUint8* Ptr() const;

Description

Gets a pointer to the data represented by the descriptor. The data cannot be changed through the returned pointer.

Return value

TUint8* A pointer to the data

TPtrC8 Left(TInt aLength) const;

Description

Extracts the leftmost part of the data.

The function does not cut or remove any data but constructs a non-modifiable pointer descriptor to represent the leftmost part of the data.

Parameters

TInt aLength The length of the data to be extracted. This value cannot be negative, otherwise the function raises a USER 22 panic. If this value is greater than the length of the descriptor, the function extracts the whole of the descriptor. In EPOC Release 5, if aLength was greater than the descriptor's length, the function raised a USER 22 panic.

Return value

TPtrC8 The 8 bit non-modifiable pointer descriptor representing the leftmost part of the data.

See also:

• Extract leftmost part of data

TPtrC8 Right(TInt aLength) const;

Description

Extracts the rightmost part of the data.

The function does not cut or remove any data but constructs a non-modifiable pointer descriptor to represent the rightmost part of the data.

Parameters

TInt aLength The length of data to be extracted. This value cannot be negative, otherwise the function raises a USER 22 panic. If this value is greater than the length of the descriptor, the function extracts the whole of the descriptor. In EPOC Release 5, if aLength was greater than the descriptor's length, the function raised a USER 22 panic.

Return value

TPtrC8 The 8 bit non-modifiable pointer descriptor representing the rightmost part of the data.

See also:

• Extract rightmost part of data

TPtrC8 Mid(TInt aPos) const;
TPtrC8 Mid(TInt aPos,TInt aLength) const;

Description

Extracts a portion of the data.

The function does not cut or remove any data but constructs a non-modifiable pointer descriptor to represent the defined portion.

The portion is identified by its starting position and by its length. If identified by position alone, the implied length is the length of the remainder of the data starting from the specified position.

Parameters

TInt aPos The starting position of the data to be extracted. This is an offset; a zero value refers to the leftmost data position. TInt aLength If specified, the length of data to be extracted. If not specified, the implied length is the length of the remainder of the data starting from the specified position.

Return value

TPtrC8 The 8 bit non-modifiable pointer descriptor representing the specified portion of the data.

See also:

• Extract middle portion of the data

const TUint8& operator[](TInt anIndex) const;

Description

Gets a reference to a single data item within this descriptor's data.

Parameters

TInt anIndex The position of the individual data item within the descriptor's data. This is an offset; a zero value refers to the leftmost data position. This value must be non-negative and less than the current length of the descriptor otherwise the operation raises a USER 21 panic.

Return value

TUint8& A reference to the data item.

See also:

• Referencing a data item

HBufC8* Alloc() const;

Description

Creates a new 8 bit heap descriptor and initialises it with a copy of this descriptor's data.

Return value

HBufC8* A pointer to the new 8 bit heap descriptor, if creation is successful. NULL, if creation of the descriptor fails.

HBufC8* AllocL() const;

Description

Creates a new 8 bit heap descriptor and initialises it with a copy of this descriptor's data.

The function leaves, if creation of the descriptor fails.

Return value

HBufC8* A pointer to the 8 bit heap descriptor, if creation is successful.

See also:

• Creating a heap descriptor

HBufC8* AllocLC() const;

Description

Creates a new 8 bit heap descriptor and initialises it with a copy of this descriptor's data

The function leaves, if creation of the descriptor fails.

Return value

HBufC8* A pointer to the 8 bit heap descriptor, if creation is successful. The pointer is also put onto the cleanup stack.

TInt Compare(const TDesC8& aDes) const;

Description

Compares this descriptor's data with the specified descriptor's data.

The comparison proceeds on a byte for byte basis. The result of the comparison is based on the difference of the first bytes to disagree.

Two descriptors are equal if they have the same length and content. Where two descriptors have different lengths and the shorter descriptor's data matches the first part of the longer descriptor's data, the shorter is considered to be less than the longer.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt Positive, if this descriptor is greater than the specified descriptor. Negative, if this descriptor is less than the specified descriptor. Zero, if both descriptors have the same length and the their contents are the same.

See also:

• Comparing data

TInt CompareC(const TDesC8& aDes) const;

Description

Compares this descriptor's data with the specified descriptor's data using the standard collation method for narrow text appropriate to the current locale.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt Positive, if this descriptor is greater than the specified descriptor. Negative, if this descriptor is less than the specified descriptor. Zero, if both descriptors have the same length and the their contents are the same.

See also:

• TDesC8::Compare()

TInt CompareF(const TDesC8& aDes) const;

Description

Compares this descriptor's folded data with the specified descriptor's folded data. The function uses the standard folding method for narrow text appropriate to the current locale.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt Positive, if this descriptor is greater than the specified descriptor. Negative, if this descriptor is less than the specified descriptor. Zero, if both descriptors have the same length and the their contents are the same.

See also:

• TDesC8::Compare()

TInt operator==(const TDesC8& aDes) const;

Description

Determines whether this descriptor's data is equal to the specified descriptor's data.

The comparison is implemented using the Compare() member function.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt True if equal, false otherwise.

See also:

• TDesC8::Compare()

TInt operator!=(const TDesC8& aDes) const;

Description

Determines whether this descriptor's data is not equal to the specified descriptor's data.

The comparison is implemented using the Compare() member function.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt True if not equal, false otherwise.

See also:

• TDesC8::Compare()

TInt operator<(const TDesC8& aDes) const;

Description

Determines whether this descriptor's data is less than the specified descriptor's data.

The comparison is implemented using the Compare() member function.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt True if less than, false otherwise.

See also:

• TDesC8::Compare()

TInt operator<=(const TDesC8& aDes) const;

Description

Determines whether this descriptor's data is less than or equal to the specified descriptor's data.

The comparison is implemented using the Compare() member function.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt True if less than or equal, false otherwise.

See also:

• TDesC8::Compare()

TInt operator>(const TDesC8& aDes) const;

Description

Determines whether this descriptor's data is greater than the specified descriptor's data.

The comparison is implemented using the Compare() member function.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt True if greater than, false otherwise.

See also:

• TDesC8::Compare()

TInt operator>=(const TDesC8& aDes) const;

Description

Determines whether this descriptor's data is greater than or equal to the specified descriptor's data.

The comparison is implemented using the Compare() member function.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TInt True if greater than, false otherwise.

See also:

• TDesC8::Compare()

TInt Locate(TChar aChar) const;

Description

Searches for the first occurrence of a character within this descriptor's data. The search starts at the beginning of the data, i.e. at the leftmost position.

Parameters

TChar aChar The character to be found.

Return value

TInt The offset of the character position from the beginning of the data.KErrNotFound, if no matching character can be found.

See also:

• Locating a character

TInt LocateF(TChar aChar) const;

Description

Searches for the first occurrence of a folded character within this descriptor's folded data. The search starts at the beginning of the data, i.e. at the leftmost position. The function uses the standard folding method for narrow text appropriate to the current locale.

Parameters

TChar aChar The character to be found.

Return value

TInt The offset of the character position from the beginning of the data.KErrNotFound, if no matching character can be found.

TInt LocateReverse(TChar aChar) const;

Description

Searches for the first occurrence of a character within this descriptor's data, searching from the end of the data. The search starts at the rightmost position.

Parameters

TChar aChar The character to be found

Return value

TInt The offset of the character position from the beginning of the data.KErrNotFound, if no matching character can be found.

TInt LocateReverseF(TChar aChar) const;

Description

Searches for the first occurrence of a folded character within this descriptor's folded data, searching from the end of the data. The search starts at the rightmost position. The function uses the standard folding method for narrow text appropriate to the current locale.

Parameters

TChar aChar The character to be found

Return value

TInt The offset of the character position from the beginning of the data.KErrNotFound, if no matching character can be found

TInt Find(const TDesC8& aDes) const;
TInt Find(const TUint8* pS,TInt aLenS) const;

Description

Searches for the first occurrence of the specified data sequence within this descriptor. Searching always starts at the beginning of this descriptor's data.

The search data can be defined within another descriptor or it may be defined as a pointer and length pair.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor containing the data sequence to be searched for. const TUint8* pS A pointer to a location containing the data sequence to be searched for. TInt aLenS The length of the data sequence to be searched for. This value must not be negative, otherwise the function raises a USER 29 panic.

Return value

TInt The offset of the data sequence from the beginning of this descriptor's data. KErrNotFound, if the data sequence cannot be found.

See also:

• Finding data

TInt FindC(const TDesC8& aDes) const;
TInt FindC(const TUint8* pS,TInt aLenS) const;

Description

Searches for the first occurrence of the specified collated data sequence within this descriptor's collated data. Searching always starts at the beginning of this descriptor's data. The function uses the standard collation method for narrow text appropriate to the current locale.

The search data can be defined within another descriptor or it may be defined as a pointer and length pair.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor containing the data sequence to be searched for. const TUint8* pS A pointer to a location containing the data sequence to be searched for. TInt aLenS The length of the data sequence to be searched for. This value must not be negative, otherwise the function raises a USER 29 panic.

Return value

TInt The offset of the data sequence from the beginning of this descriptor's data. KErrNotFound, if the data sequence cannot be found.

TInt FindF(const TDesC8& aDes) const;
TInt FindF(const TUint8* pS,TInt aLenS) const;

Description

Searches for the first occurrence of the specified folded data sequence within this descriptor's folded data. Searching always starts at the beginning of this descriptor's data. The function uses the standard folding method for narrow text appropriate to the current locale.

The search data can be defined within another descriptor or it may be defined as a pointer and length pair.

Parameters

const TDesC8& aDes The 8 bit non modifable descriptor containing the data sequence to be searched for. const TUint8* pS A pointer to a location containing the data sequence to be searched for. TInt aLenS The length of the data sequence to be searched for. This value must not be negative, otherwise the function raises a USER 29 panic.

Return value

TInt The offset of the data sequence from the beginning of this descriptor's data. KErrNotFound, if the data sequence cannot be found.

TInt Match(const TDesC8& aDes) const;

Description

Searches this descriptor's data for a match with the match pattern supplied in the specified descriptor.

The match pattern can contain the wildcard characters "*" and "?", where "*" matches zero or more consecutive occurrences of any character and "?" matches a single occurrence of any character.

Parameters

const TDesC8& aDes An 8 bit non modifable descriptor containing the match pattern.

Return value

TInt If a match is found, the offset within this descriptor's data where the match first occurs. KErrNotFound, if there is no match.

See also:

• Pattern matching

TInt MatchC(const TDesC8& aDes) const;

Description

Searches this descriptor's collated data for a match with the collated match pattern supplied in the specified descriptor. The function uses the standard collation method for narrow text appropriate to the current locale.

The match pattern can contain the wildcard characters "*" and "?", where "*" matches zero or more consecutive occurrences of any character and "?" matches a single occurrence of any character.

Parameters

const TDesC8& aDes An 8 bit non modifable descriptor containing the match pattern.

Return value

TInt If a match is found, the offset within this descriptor's data where the match first occurs. KErrNotFound, if there is no match.

TInt MatchF(const TDesC8& aDes) const;

Description

Searches this descriptor's folded data for a match with the folded match pattern supplied in the specified descriptor. The function uses the standard folding method for narrow text appropriate to the current locale.

The match pattern can contain the wildcard characters "*" and "?", where "*" matches zero or more consecutive occurrences of any character and "?" matches a single occurrence of any character.

Parameters

const TDesC8& aDes An8 bit non modifable descriptor containing the match pattern.

Return value

TInt If a match is found, the offset within this descriptor's data where the match first occurs. KErrNotFound, if there is no match.