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Base E32_EKA2 »
HBufC16
Location:
e32des16.h
Link against: euser.lib
class HBufC16 : public TBufCBase16;
Description
16-bit heap descriptor.
This is a descriptor class which provides a buffer of fixed length, allocated on the heap, for containing and accessing data.
The class is intended for instantiation.
Heap descriptors have the important property that they can be made larger or smaller, changing the size of the descriptor
buffer. This is achieved by reallocating the descriptor. Unlike the behaviour of dynamic buffers, reallocation is not done
automatically.
Data is intended to be accessed, but not modified; however, it can be completely replaced using the assignment operators of
this class. The base class (TDesC16
) provides the functions through which the data is accessed.
The descriptor is hosted by a heap cell, and the 16-bit data that the descriptor represents is part of the descriptor object
itself. The size of the cell depends on the requested maximum length of the descriptor buffer when the descriptor is created
or re-allocated.
It is important to note that the size of the allocated cell, and, therefore, the resulting maximum length of the descriptor,
may be larger than requested due to the way memory is allocated in Symbian OS. The amount by which this may be rounded up
depends on the platform and build type.
Derivation
TBufCBase16
- No description.
HBufC16
- 16-bit heap descriptor
Members
Defined in HBufC16
:
Des()
, New()
, NewL()
, NewL()
, NewLC()
, NewLC()
, NewMax()
, NewMaxL()
, NewMaxLC()
, ReAlloc()
, ReAllocL()
, operator=()
, operator=()
, operator=()
See also:
Construction and destruction
static IMPORT_C HBufC16 *NewL(TInt aMaxLength);
Description
Creates, and returns a pointer to, a new 16-bit heap descriptor, and leaves on failure.
The heap descriptor is empty and its length is zero.
Data can, subsequently, be assigned into it using the assignment operators.
Parameters
TInt aMaxLength |
The requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested.
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Return value
HBufC16 *
|
A pointer to the new 16-bit heap descriptor. The function leaves, if the new 16-bit heap descriptor cannot be created.
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Panic codes
USER |
18 if aMaxLength is negative.
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See also:
static IMPORT_C HBufC16 *NewLC(TInt aMaxLength);
Description
Creates, adds a pointer onto the cleanup stack and returns a pointer to, a new 16-bit heap descriptor; leaves on failure.
The heap descriptor is empty and its length is zero.
Data can, subsequently, be assigned into it using the assignment operators.
Parameters
TInt aMaxLength |
The requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested.
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Return value
HBufC16 *
|
A pointer to the new 16-bit heap descriptor. The function leaves, if the new 16-bit heap descriptor cannot be created.
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Panic codes
USER |
18 if aMaxLength is negative.
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See also:
static IMPORT_C HBufC16 *NewL(RReadStream &aStream, TInt aMaxLength);
Description
Parameters
RReadStream &aStream |
|
TInt aMaxLength |
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Return value
static IMPORT_C HBufC16 *NewLC(RReadStream &aStream, TInt aMaxLength);
Description
Parameters
RReadStream &aStream |
|
TInt aMaxLength |
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Return value
static IMPORT_C HBufC16 *New(TInt aMaxLength);
Description
Creates, and returns a pointer to, a new 16-bit heap descriptor.
The heap descriptor is empty and its length is zero.
Data can, subsequently, be assigned into it using the assignment operators.
Parameters
TInt aMaxLength |
The requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested.
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Return value
HBufC16 *
|
A pointer to the new 16-bit heap descriptor. NULL, if the 16-bit heap descriptor cannot be created.
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Panic codes
USER |
18 if aMaxLength is negative.
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See also:
static IMPORT_C HBufC16 *NewMax(TInt aMaxLength);
Description
Creates, and returns a pointer to, a new 16-bit heap descriptor.
No data is assigned into the new descriptor but its length is set to aMaxLength.
Data can, subsequently, be assigned into it using the assignment operators.
Parameters
TInt aMaxLength |
The requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested. This also means that the resulting maximum length of the descriptor
may be greater than its length.
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Return value
HBufC16 *
|
A pointer to the new 16-bit heap descriptor. NULL, if the new 16-bit heap descriptor cannot be created.
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Panic codes
USER |
18 if aMaxLength is negative.
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See also:
static IMPORT_C HBufC16 *NewMaxL(TInt aMaxLength);
Description
Creates, and returns a pointer to, a new 16-bit heap descriptor; leaves on failure.
No data is assigned into the new descriptor but its length is set to aMaxLength.
Data can, subsequently, be assigned into it using the assignment operators.
Parameters
TInt aMaxLength |
The requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested. This also means that the resulting maximum length of the descriptor
may be greater than its length.
|
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Return value
HBufC16 *
|
A pointer to the new 16-bit heap descriptor. The function leaves, if the new 16-bit heap descriptor cannot be created.
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Panic codes
USER |
18 if aMaxLength is negative.
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See also:
static IMPORT_C HBufC16 *NewMaxLC(TInt aMaxLength);
Description
Creates, adds a pointer onto the cleanup stack and returns a pointer to, a new 16-bit heap descriptor; leaves on failure.
No data is assigned into the new descriptor but its length is set to aMaxLength.
Data can, subsequently, be assigned into it using the assignment operators.
Parameters
TInt aMaxLength |
The requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested.
|
|
Return value
HBufC16 *
|
A pointer to the new 16-bit heap descriptor. This is also put onto the cleanup stack. The function leaves, if the new 16-bit
heap descriptor cannot be created.
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Panic codes
USER |
18 if aMaxLength is negative.
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See also:
IMPORT_C HBufC16 &operator=(const TUint16 *aString);
Description
Copies data into this 16-bit heap descriptor replacing any existing data.
The length of this descriptor is set to reflect the new data.
Note that the maximum length of this (target) descriptor is the length of the descriptor buffer in the allocated host heap
cell; this may be greater than the maximum length specified when this descriptor was created or last re-allocated.
Parameters
const TUint16 *aString |
A pointer to a zero-terminated string.
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Return value
HBufC16 &
|
A reference to this 16-bit heap descriptor.
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Panic codes
USER |
11 if the length of the string, excluding the zero terminator, is greater than the maximum length of this (target) descriptor.
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IMPORT_C HBufC16 &operator=(const TDesC16 &aDes);
Description
Copies data into this 16-bit heap descriptor replacing any existing data.
The length of this descriptor is set to reflect the new data.
Note that the maximum length of this (target) descriptor is the length of the descriptor buffer in the allocated host heap
cell; this may be greater than the maximum length specified when this descriptor was created or last re-allocated.
Parameters
const TDesC16 &aDes |
A 16-bit non-modifiable descriptor.
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Return value
HBufC16 &
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A reference to this 16-bit heap descriptor.
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Panic codes
USER |
11 if the length of the descriptor aDes is greater than the maximum length of this (target) descriptor
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inline HBufC16 &operator=(const HBufC16 &aLcb);
Description
Copies data into this 16-bit heap descriptor replacing any existing data.
The length of this descriptor is set to reflect the new data.
Note that the maximum length of this (target) descriptor is the length of the descriptor buffer in the allocated host heap
cell; this may be greater than the maximum length specified when this descriptor was created or last re-allocated.
Parameters
const HBufC16 &aLcb |
The source 16-bit heap descriptor.
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Return value
HBufC16 & |
A reference to this 16-bit heap descriptor.
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Panic codes
USER |
11, if the length of the descriptor aLcb is greater than the maximum length of this (target) descriptor
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IMPORT_C HBufC16 *ReAlloc(TInt aMaxLength);
Description
Expands or contracts this 16-bit heap descriptor.
This is done by:
1. creating a new heap descriptor.
2. copying the original data into the new descriptor.
3. deleting the original descriptor.
Parameters
TInt aMaxLength |
The new requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested.
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Return value
HBufC16 *
|
A pointer to the new expanded or contracted 16-bit heap descriptor - the original descriptor is deleted. NULL, if the new
16-bit heap descriptor cannot be created - the original descriptor remains unchanged.
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Panic codes
USER |
14 if aMaxLength is less than the length of the existing data.
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USER |
18 if aMaxLength is negative.
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IMPORT_C HBufC16 *ReAllocL(TInt aMaxLength);
Description
Expands or contracts this 16-bit heap descriptor; leaves on failure.
This is done by:
1. creating a new heap descriptor.
2. copying the original data into the new descriptor.
3. deleting the original descriptor.
Parameters
TInt aMaxLength |
The new requested maximum length of the descriptor. Note that the resulting heap cell size and, therefore, the resulting maximum
length of the descriptor may be larger than requested.
|
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Return value
HBufC16 *
|
A pointer to the new expanded or contracted 16-bit heap descriptor - the original descriptor is deleted. The function leaves,
if the new 16-bit heap descriptor cannot be created - the original descriptor remains unchanged.
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Panic codes
USER |
14 if aMaxLength is less than the length of the existing data.
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USER |
18 if aMaxLength is negative.
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IMPORT_C TPtr16 Des();
Description
Creates and returns a 16-bit modifiable pointer descriptor for the data represented by this 16-bit heap descriptor.
The content of a heap descriptor normally cannot be altered, other than by complete replacement of the data. Creating a modifiable
pointer descriptor provides a way of changing the data.
The modifiable pointer descriptor is set to point to this heap descriptor's data.
The length of the modifiable pointer descriptor is set to the length of this heap descriptor.
The maximum length of the modifiable pointer descriptor is set to the length of the heap descriptor's buffer. Note that the
maximum length is the length of the descriptor buffer in the allocated host heap cell; this may be greater than the maximum
length requested when this descriptor was originally created or last re-allocated.
When data is modified through this new pointer descriptor, the lengths of both it and this heap descriptor are changed.
Note that it is a common mistake to use Des()
to create a TDesC16
& reference. While not incorrect, it is simpler and much more efficient to simply dereference the heap descriptor.
Return value
TPtr16
|
A 16-bit modifiable pointer descriptor representing the data in this 16-bit heap descriptor.
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