Class TDesC16

class TDesC16;

Description

Abstract base class for 16-bit descriptors.

The class encapsulates the data member containing the length of data represented by a 16-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 16-bit (i.e. double 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.

Members

Defined in TDesC16:
Alloc(), AllocL(), AllocLC(), AtC(), Compare(), CompareC(), CompareC(), CompareF(), DoSetLength(), EIsNotPrefix, EIsPrefix, EMightBePrefix, Find(), Find(), FindC(), FindC(), FindC(), FindC(), FindF(), FindF(), HasPrefixC(), Left(), Length(), Locate(), LocateF(), LocateReverse(), LocateReverseF(), Match(), MatchC(), MatchC(), MatchC(), MatchF(), Mid(), Mid(), Ptr(), Right(), Size(), TDesC16(), TDesC16(), TPrefix, Type(), operator!=(), operator>(), operator>=(), operator<(), operator<=(), operator==(), operator[]()

See also:

• TDesC
• TPtrC16

protected: inline TDesC16();

Description

protected: inline TDesC16(TInt aType, TInt aLength);

Description

Parameters

TInt aType TInt aLength

inline TBool operator<(const TDesC16 &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 TDesC16 &aDes The 16-bit non-modifable descriptor whose data is to be compared with this descriptor's data.

Return value

TBool True if less than, false otherwise.

inline TBool operator<=(const TDesC16 &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 TDesC16 &aDes The 16-bit non- modifiable descriptor whose data is to be compared with this descriptor's data.

Return value

TBool True if less than or equal, false otherwise.

inline TBool operator>(const TDesC16 &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 TDesC16 &aDes The 16-bit non-modifiable descriptor whose data is to be compared with this descriptor's data.

Return value

TBool True if greater than, false otherwise.

inline TBool operator>=(const TDesC16 &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 TDesC16 &aDes The 16-bit non-modifiable descriptor whose data is to be compared with this descriptor's data.

Return value

TBool True if greater than or equal, false otherwise.

inline TBool operator==(const TDesC16 &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 TDesC16 &aDes The 16-bit non-modifiable descriptor whose data is to be compared with this descriptor's data.

Return value

TBool True if equal, false otherwise.

inline TBool operator!=(const TDesC16 &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 TDesC16 &aDes The 16-bit non-modifiable descriptor whose data is to be compared with this descriptor's data.

Return value

TBool True if not equal, false otherwise.

inline const TUint16 &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 value; a zero value refers to the leftmost data position.

Return value

const TUint16 & A reference to the data item.

Panic codes

USER 9, if anIndex is negative or greater than or equal to the current length of the descriptor.

inline TInt Length() const;

Description

Gets the length of the data.

This is the number of 16-bit values or data items represented by the descriptor.

Return value

TInt The length of the data represented by the descriptor.

inline 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. This is always twice the length.

IMPORT_C const TUint16 *Ptr() const;

Description

Gets a pointer to the data represented by the descriptor.

The data cannot be changed through the returned pointer.

Return value

const TUint16 * A pointer to the data

IMPORT_C TInt Compare(const TDesC16 &aDes) const;

Description

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

The comparison proceeds on a double-byte for double byte basis. The result of the comparison is based on the difference of the first pair of 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 TDesC16 &aDes The 16-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.

IMPORT_C TInt CompareF(const TDesC16 &aDes) const;

Description

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

Note that folding is locale-independent behaviour. It is also important to note that there can be no guarantee that folding is in any way culturally appropriate, and should not be used for comparing strings in natural language; use CompareC() for this.

Parameters

const TDesC16 &aDes The 16-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

• Folding

See also:

• TDesC16::Compare()

IMPORT_C TInt CompareC(const TDesC16 &aDes) const;

Description

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

Parameters

const TDesC16 &aDes The 16-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 the content of both descriptors match.

See also

• Collation

See also:

• TDesC16::Compare()

IMPORT_C TInt CompareC(const TDesC16 &aDes, TInt aMaxLevel, const TCollationMethod *aCollationMethod) const;

Description

Compares this descriptor's data with the specified descriptor's data to the specified maximum collation level and using the specified collation method.

If no collation method is supplied, a default method is used that uses a locale-independent collation table. This means that sorting and matching will not be based on the current locale.

This function is only defined for 16-bit (Unicode) build variants. This means that the function is not defined for 8-bit build variants, even when an explicit 16-bit descriptor is used.

Strings may match even if the lengths of their respective descriptors are different.

Parameters

const TDesC16 &aDes The 16-bit non-modifable descriptor whose data is to be compared with this descriptor's data. TInt aMaxLevel The maximum collation level. This is an integer with values: 0, 1, 2 or 3, which, effectively, determines how 'tight' the matching should be. Level 3 is always used if the aim is to sort strings. const TCollationMethod *aCollationMethod A pointer to the collation method or NULL. Collation methods can be retrieved by calls to Mem::CollationMethodByIndex() and Mem::CollationMethodById(). Specifying NULL means that the default method is used.

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 the content of both descriptors match.

See also

• Collation

See also:

• Mem::CollationMethodByIndex()
• Mem::CollationMethodById()
• TDesC16::Compare()

IMPORT_C TInt Match(const TDesC16 &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.

Note that there is no 'escape character', which means that it is not possible to match either the "*" character itself or the "?" character itself using this function.

Parameters

const TDesC16 &aDes A 16-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.

IMPORT_C TInt MatchF(const TDesC16 &aDes) const;

Description

Searches this descriptor's folded data for a match with the folded 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.

Note that folding is locale-independent behaviour. It is also important to note that there can be no guarantee that folding is in any way culturally appropriate, and should not be used for matching strings in natural language; use MatchC() for this.

Note that there is no 'escape character', which means that it is not possible to match either the "*" character itself or the "?" character itself using this function.

Parameters

const TDesC16 &aDes A 16-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

• Folding

See also:

• TDesC16::MatchC()

IMPORT_C TInt MatchC(const TDesC16 &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 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.

Note that there is no 'escape character', which means that it is not possible to match either the "*" character itself or the "?" character itself using this function.

Parameters

const TDesC16 &aDes A 16-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

• Collation

IMPORT_C TInt MatchC(const TDesC16 &aPattern, TInt aWildChar, TInt aWildSequenceChar, TInt aEscapeChar, TInt aMaxLevel=3, const TCollationMethod *aCollationMethod=NULL) 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 appropriate to the current locale.

The match pattern can contain the wildcard characters specified by aWildChar and aWildSequenceChar parameters, where aWildSequenceChar matches zero or more consecutive occurrences of any character and aWildChar matches a single occurrence of any character.

Parameters

const TDesC16 &aPattern A 16-bit non-modifable descriptor containing the match pattern. TInt aWildChar Wild card character which may be specified for aSearchTerm. TInt aWildSequenceChar Wild card sequence character which may be specified for aSearchTerm. TInt aEscapeChar The escape character, or 0 if there is to be none. The escape character removes any special meaning from the subsequent character. For example, if the escape, wild card and wild sequence characters are \, ? And * respectively, the search term "\?\*\\" matches only the candidate string "?*\"; TInt aMaxLevel Determines the tightness of the collation. At level 0, only character identities are distinguished. At level 1 accents are distinguished as well. At level 2 case is distinguishes as well. At level 3 all valid different Unicode characters are considered different. const TCollationMethod *aCollationMethod A pointer to the collation method or NULL. Collation methods can be retrieved by calls to Mem::CollationMethodByIndex() and Mem::CollationMethodById(). Specifying NULL means that the default method is used.

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

• Collation

IMPORT_C TInt MatchC(const TDesC16 &aPattern, const TCollationMethod *aCollationMethod, TInt aMaxLevel=3, TInt aWildChar= '?', TInt aWildSequenceChar= '*', TInt aEscapeChar=0) 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 appropriate to the current locale.

The match pattern can contain the wildcard characters specified by aWildChar and aWildSequenceChar parameters, where aWildSequenceChar matches zero or more consecutive occurrences of any character and aWildChar matches a single occurrence of any character.

Parameters

const TDesC16 &aPattern A 16-bit non-modifable descriptor containing the match pattern. const TCollationMethod *aCollationMethod A pointer to the collation method. Collation methods can be retrieved by calls to Mem::CollationMethodByIndex(), Mem::CollationMethodById() or by custom defined name. Flags can be set on definition of the custom TCollationMethod, or by const_cast-ing the returned pointer and setting the iFlags field directly. TInt aMaxLevel Determines the tightness of the collation. Defaulted to 3 if omitted. At level 0, only character identities are distinguished. At level 1 accents are distinguished as well. At level 2 case is distinguishes as well. At level 3 all valid different Unicode characters are considered different. TInt aWildChar Wild card character which may be specified for aSearchTerm. Defaulted to '?' if omitted. TInt aWildSequenceChar Wild card sequence character which may be specified for aSearchTerm. Defaulted to '*' if omitted. TInt aEscapeChar The escape character, or 0 if there is to be none. The escape character removes any special meaning from the subsequent character. For example, if the escape, wild card and wild sequence characters are \, ? And * respectively, the search term "\?\*\\" matches only the candidate string "?*\". Defaulted to 0 if omitted.

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

• Collation

IMPORT_C 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.

IMPORT_C 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.

IMPORT_C TInt Find(const TDesC16 &aDes) 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.

Parameters

const TDesC16 &aDes The 16-bit non-modifiable descriptor containing the data sequence to be searched for.

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.

IMPORT_C TInt Find(const TUint16 *aBuf, TInt aLen) 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.

Parameters

const TUint16 *aBuf A pointer to a location containing the data sequence to be searched for. TInt aLen The length of the data sequence to be searched for. This value must not be negative, otherwise the function raises a 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.

Panic codes

USER 17 if aLenS is negative.

IMPORT_C TPrefix HasPrefixC(const TDesC16 &aPossiblePrefix, TInt aLevel, const TCollationMethod *aCollationMethod) const;

Description

Compares aPossiblePrefix against the start of the descriptor, using a collated comparison.

0: Only check character identities.

1: Check accents as well.

2: Check case as well.

3: Check Unicode values.

Currently only level 0 is supported.

Parameters

const TDesC16 &aPossiblePrefix TInt aLevel The maximum level at which to perform the collation. const TCollationMethod *aCollationMethod The collation method to be used for the matching.

Return value

TPrefix EIsPrefix, if aPossiblePrefix can be extended to be equivalent to the text at the start of this descriptor. EIsNotPrefix if aPossiblePrefix cannot be extended to be equivalent to the text at the start of this descriptor. EMightBePrefix if it currently does not seem to be a prefix, but it is possible that it could be extended to become equivalent to text at the start of this descriptor. EMightBePrefix is returned in cases where it would be expensive to determine for sure.

IMPORT_C TPtrC16 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. If this value is greater than the length of the descriptor, the function extracts the whole of the descriptor.

Return value

TPtrC16 The 16-bit non-modifiable pointer descriptor representing the leftmost part of the data.

Panic codes

USER 10 if aLength is negative.

IMPORT_C TPtrC16 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. If this value is greater than the length of the descriptor, the function extracts the whole of the descriptor.

Return value

TPtrC16 The 16-bit non-modifiable pointer descriptor representing the rightmost part of the data.

Panic codes

USER 10 if aLength is negative.

IMPORT_C TPtrC16 Mid(TInt aPos) 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 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 value; a zero value refers to the leftmost data position.

Return value

TPtrC16 The 16-bit non-modifiable pointer descriptor representing the specified portion of the data.

Panic codes

USER 10 if aPos is negative or aPos is greater than the length of the descriptor.

IMPORT_C TPtrC16 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.

Parameters

TInt aPos The starting position of the data to be extracted. This is an offset value; a zero value refers to the leftmost data position. TInt aLength The length of data to be extracted.

Return value

TPtrC16 The 16-bit non-modifiable pointer descriptor representing the specified portion of the data.

Panic codes

USER 10 if aPos is negative or aPos plus aLength is greater than the length of the descriptor.

IMPORT_C 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.

Note that folding is locale-independent behaviour. It is also important to note that there can be no guarantee that folding is in any way culturally appropriate, and should not be used for searching strings in natural language.

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

• Folding

IMPORT_C 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.

Note that folding is locale-independent behaviour. It is also important to note that there can be no guarantee that folding is in any way culturally appropriate, and should not be used for searching strings in natural language.

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

• Folding

IMPORT_C TInt FindF(const TDesC16 &aDes) 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.

Note that folding is locale-independent behaviour. It is also important to note that there can be no guarantee that folding is in any way culturally appropriate, and should not be used for finding strings in natural language; use FindC() for this.

Parameters

const TDesC16 &aDes The 16-bit non-modifable descriptor containing the data sequence to be searched for.

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. Zero, if the length of the search data sequence is zero.

See also

• Folding

See also:

• TDesC16::FindC()

IMPORT_C TInt FindF(const TUint16 *aBuf, TInt aLen) 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.

Note that folding is locale-independent behaviour. It is also important to note that there can be no guarantee that folding is in any way culturally appropriate, and should not be used for finding strings in natural language; use FindC() for this.

Parameters

const TUint16 *aBuf A pointer to a location containing the data sequence to be searched for. TInt aLen The length of the data sequence to be searched for. This value must not be negative, otherwise the function raises a 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. Zero, if the length of the search data sequence is zero.

Panic codes

USER 17 if aLenS is negative

See also

• Folding

See also:

• TDesC16::FindC()

IMPORT_C TInt FindC(const TDesC16 &aDes) 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 appropriate to the current locale.

Parameters

const TDesC16 &aDes The 16-bit non-modifable descriptor containing the data sequence to be searched for.

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

• Collation

IMPORT_C TInt FindC(const TUint16 *aBuf, TInt aLen) 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 appropriate to the current locale.

Parameters

const TUint16 *aBuf A pointer to a location containing the data sequence to be searched for. TInt aLen The length of the data sequence to be searched for.

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.

Panic codes

USER 17 if aLength is negative.

See also

• Collation

IMPORT_C TInt FindC(const TUint16 *aText, TInt aLength, TInt aMaxLevel) const;

Description

Searches for the first occurrence of the specified collated data sequence within this descriptor's collated data to the specified maximum collation level.

Parameters

const TUint16 *aText A pointer to a location containing the data sequence to be searched for. TInt aLength The length of the data sequence to be searched for. TInt aMaxLevel The maximum collation level. This is an integer with values: 0, 1, 2 or 3, which, effectively, determines how 'tight' the matching should be. Level 3 is always used if the aim is to sort strings.

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

• Collation

IMPORT_C TInt FindC(const TDesC16 &aDes, TInt &aLengthFound, const TCollationMethod &aMethod, TInt aMaxLevel) 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 appropriate to the current locale.

Parameters

const TDesC16 &aDes The 16-bit non-modifable descriptor containing the data sequence to be searched for. TInt &aLengthFound A refernce to the maximal length of the match found in the candidate string. KErrNotFound, if the data sequence cannot be found. const TCollationMethod &aMethod TInt aMaxLevel The maximum collation level. This is an integer with values: 0, 1, 2 or 3, which, effectively, determines how 'tight' the matching should be. Level 3 is always used if the aim is to sort strings.

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

• Collation

IMPORT_C HBufC16 *Alloc() const;

Description

Creates a new 16-bit heap descriptor and initialises it with a copy of this descriptor's data.

Return value

HBufC16 * A pointer to the new 16-bit heap descriptor, if creation is successful. NULL, if creation of the descriptor fails.

IMPORT_C HBufC16 *AllocL() const;

Description

Creates a new 16-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

HBufC16 * A pointer to the 16-bit heap descriptor, if creation is successful.

IMPORT_C HBufC16 *AllocLC() const;

Description

Creates a new 16-bit heap descriptor, initialises it with a copy of this descriptor's data, and puts a pointer to the descriptor onto the cleanup stack.

The function leaves, if creation of the descriptor fails.

Return value

HBufC16 * A pointer to the 16-bit heap descriptor, if creation is successful. The pointer is also put onto the cleanup stack.

protected: inline TInt Type() const;

Description

Return value

TInt

protected: inline void DoSetLength(TInt aLength);

Description

Parameters

TInt aLength

protected: IMPORT_C const TUint16 &AtC(TInt anIndex) const;

Description

Parameters

TInt anIndex

Return value

const TUint16 &

TPrefix

Description

A value returned by a call to HasPrefixC().

EIsPrefix Indicates that a supplied prefix can be extended to be equivalent to the text at the start of a descriptor. EMightBePrefix Indicates that a supplied prefix does not seem to be a prefix, but it is possible that it could be extended to become equivalent to text at the start of this descriptor. EIsNotPrefix Indicates that a supplied prefix cannot be extended to be equivalent to the text at the start of a descriptor.