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class CBufBase : public CBase;
Defines the interface for dynamic buffers.
The basic functions, CBufBase::InsertL(TInt,const TDesC8 &), CBufBase::Read(TInt,TDes8 &)const, CBufBase::Write(TInt,const TDesC8 &), CBufBase::Delete(TInt,TInt), CBufBase::Reset() and CBufBase::Size()const, transfer data between the buffer and other places, and allow that data to be deleted
The CBufBase::ExpandL(TInt,TInt) and Resize() functions allow some operations to be carried out with greater efficiency
ACBufBase::Compress() function frees (back to the heap) any space which may have been allocated, but not used
CBufBase::Ptr(TInt) and CBufBase::BackPtr(TInt) allow look-up of contiguous data from any given position, forward or backward
CBase -
Base class for all classes to be instantiated on the heap.
CBufBase -
Defines the interface for dynamic buffers.
Defined in CBufBase:
BackPtr(TInt)Gets a pointer descriptor to represent data from just before the specified data ...Compress()Compresses the buffer so as to occupy minimal space.Delete(TInt,TInt)Deletes data from the buffer.DoInsertL(TInt,const TAny *,TInt)ExpandL(TInt,TInt)Inserts an uninitialised region into the buffer.InsertL(TInt,const TAny *,TInt)Inserts bytes of data from the specified address into the buffer.InsertL(TInt,const TDesC8 &)Inserts data into the buffer.InsertL(TInt,const TDesC8 &,TInt)Inserts the specified number of bytes of data from a descriptor into the buffer.Ptr(TInt)Gets a pointer descriptor to represent the data from the specified position to t...Read(TInt,TAny *,TInt)constReads the specified number of bytes of data from the buffer into a specified add...Read(TInt,TDes8 &)constReads data from the buffer into a descriptor.Read(TInt,TDes8 &,TInt)constReads the specified number of bytes of data from the buffer into a descriptor.Reset()Deletes all data in the buffer.ResizeL(TInt)Re-sizes the buffer to the specified size.Size()constGets the number of data bytes in the buffer.Write(TInt,const TAny *,TInt)Writes the specified number of bytes of data from the specified address to the b...Write(TInt,const TDesC8 &)Writes data from a descriptor to the buffer.Write(TInt,const TDesC8 &,TInt)Writes the specified number of bytes of data from a descriptor to the buffer.iExpandSizeiSize~CBufBase()Destructor Inherited from CBase:
Delete(CBase *)Deletes the specified object.Extension_(TUint,TAny *&,TAny *)Extension function operator new(TUint)Allocates the object from the heap and then initialises its contents to binary z...operator new(TUint,TAny *)Initialises the object to binary zeroes.operator new(TUint,TLeave)Allocates the object from the heap and then initialises its contents to binary z...operator new(TUint,TLeave,TUint)Allocates the object from the heap and then initialises its contents to binary z...operator new(TUint,TUint)Allocates the object from the heap and then initialises its contents to binary z...|
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inline TInt Size() const;
Gets the number of data bytes in the buffer.
Note that the number of heap bytes used by the buffer may be greater than its size, because there is typically extra room
to allow for expansion. Use the CBufBase::Compress() function to reduce the extra allocation as much as possible.
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IMPORT_C void Reset();
Deletes all data in the buffer.
Its behaviour is the same as calling Delete(0,CBufBase::Size()const). The buffer is compressed before the function returns.
IMPORT_C void Read(TInt aPos, TDes8 &aDes) const;
Reads data from the buffer into a descriptor.
Data, starting at the specified buffer position is written to the descriptor, filling the descriptor.
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IMPORT_C void Read(TInt aPos, TDes8 &aDes, TInt aLength) const;
Reads the specified number of bytes of data from the buffer into a descriptor.
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IMPORT_C void Read(TInt aPos, TAny *aPtr, TInt aLength) const;
Reads the specified number of bytes of data from the buffer into a specified address.
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IMPORT_C void Write(TInt aPos, const TDesC8 &aDes);
Writes data from a descriptor to the buffer.
The data in the descriptor overwrites the data in the buffer from the insertion point onwards.
No new space is allocated; this function cannot fail (provided the parameters are specified within the bounds of the buffer and descriptor).
No shuffling occurs; new data is written to the memory locations occupied by the data it overwrites.
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IMPORT_C void Write(TInt aPos, const TDesC8 &aDes, TInt aLength);
Writes the specified number of bytes of data from a descriptor to the buffer.
The data in the descriptor overwrites the data in the buffer from the insertion point onwards.
No new space is allocated; this function cannot fail (provided the parameters are specified within the bounds of the buffer and descriptor).
No shuffling occurs; new data is written to the memory locations occupied by the data it overwrites.
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IMPORT_C void Write(TInt aPos, const TAny *aPtr, TInt aLength);
Writes the specified number of bytes of data from the specified address to the buffer.
The data in the buffer is overwritten from the insertion point onwards.
No new space is allocated; this function cannot fail (provided the parameters are specified within the bounds of the buffer and descriptor).
No shuffling occurs: new data is written to the memory locations occupied by the data it overwrites.
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IMPORT_C void InsertL(TInt aPos, const TDesC8 &aDes);
Inserts data into the buffer.
Data at and beyond the insertion position is moved to make way for the inserted data. Data before the insertion position remains in place.
Notes:
1. Insertion may require more buffer space to be allocated.
2. In the case of flat buffers, the buffer is extended by a ReAllocL() of the buffer's heap cell, to the smallest multiple of the granularity that will contain the data required. If this reallocation fails, the insertion is impossible and a leave occurs.
3. In the case of segmented buffers, a reallocation is performed if the segment containing the insertion position has insufficient space, and immediately-neighbouring segments cannot be used to contain the new data. As many new segments as are necessary to contain the inserted data are allocated. Each new segment's length is the buffer's granularity. If extension or new allocation fails, a leave occurs.
4. Insertion may also require data to be shuffled. In the case of flat buffers, data beyond the insertion point is shuffled up to create a gap; the new data is then inserted into this gap. In the case of segmented buffers, shuffling is minimised by inserting the new data into newly-allocated buffers, and shuffling only immediately-neighbouring buffers if possible. This may result in some wastage of space, but is much more time-efficient for large amounts of data.
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IMPORT_C void InsertL(TInt aPos, const TDesC8 &aDes, TInt aLength);
Inserts the specified number of bytes of data from a descriptor into the buffer.
aLength bytes of data from aDes are inserted into the buffer at aPos. Data at and beyond the insertion position is moved to make way for the inserted data. Data before the insertion position remains in place.
Notes:
1. Insertion may require more buffer space to be allocated.
2. In the case of flat buffers, the buffer is extended by a ReAllocL() of the buffer's heap cell, to the smallest multiple of the granularity that will contain the data required. If this reallocation fails, the insertion is impossible and a leave occurs.
3. In the case of segmented buffers, a reallocation is performed if the segment containing the insertion position has insufficient space, and immediately-neighbouring segments cannot be used to contain the new data. As many new segments as are necessary to contain the inserted data are allocated. Each new segment's length is the buffer's granularity. If extension or new allocation fails, a leave occurs.
4. Insertion may also require data to be shuffled. In the case of flat buffers, data beyond the insertion point is shuffled up to create a gap: the new data is then inserted into this gap. In the case of segmented buffers, shuffling is minimised by inserting the new data into newly-allocated buffers, and shuffling only immediately-neighbouring buffers if possible. This may result in some wastage of space, but is much more time-efficient for large amounts of data.
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IMPORT_C void InsertL(TInt aPos, const TAny *aPtr, TInt aLength);
Inserts bytes of data from the specified address into the buffer.
Inserts aLength bytes of data found at address aPtr into the buffer at aPos. Data at and beyond the insertion position is moved to make way for the inserted data. Data before the insertion position remains in place.
Notes:
1. Insertion may require more buffer space to be allocated.
2. In the case of flat buffers, the buffer is extended by a ReAllocL() of the buffer's heap cell, to the smallest multiple of the granularity that will contain the data required. If this reallocation fails, the insertion is impossible and a leave occurs.
2. In the case of segmented buffers, a reallocation is performed if the segment containing the insertion position has insufficient space, and immediately-neighbouring segments cannot be used to contain the new data. As many new segments as are necessary to contain the inserted data are allocated. Each new segment's length is the buffer's granularity. If extension or new allocation fails, a leave occurs.
4. Insertion may also require data to be shuffled. In the case of flat buffers, data beyond the insertion point is shuffled up to create a gap: the new data is then inserted into this gap. In the case of segmented buffers, shuffling is minimised by inserting the new data into newly-allocated buffers, and shuffling only immediately-neighbouring buffers if possible. This may result in some wastage of space, but is much more time-efficient for large amounts of data.
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IMPORT_C void ExpandL(TInt aPos, TInt aLength);
Inserts an uninitialised region into the buffer.
Data at and beyond the insertion position is moved to make way for the inserted region. Data before the insertion position remains in place.
Note:
1. The inserted region is not initialised. After using CBufBase::ExpandL(TInt,TInt), you should then use a series of CBufBase::Write(TInt,const TDesC8 &)s to fill this region with data.
2. Use CBufBase::ExpandL(TInt,TInt) followed by a series of CBufBase::Write(TInt,const TDesC8 &)s when you know the amount of data to be inserted, in advance. It is more efficient than a series of CBufBase::InsertL(TInt,const TDesC8 &)s. In addition, once the result of the CBufBase::ExpandL(TInt,TInt) has been checked, it is guaranteed that the CBufBase::Write(TInt,const TDesC8 &)s do not leave, which can sometimes be useful.
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IMPORT_C void ResizeL(TInt aSize);
Re-sizes the buffer to the specified size.
The new size can be larger or smaller than the existing size.
If the new size is larger than the existing size, the buffer is expanded by adding uninitialised data to the end of it.
If the new size is smaller than the existing size, the buffer is reduced; any data at the end of the buffer is lost.
Notes:
1. If the new size is larger than the existing size, the function is equivalent to Delete(aSize,CBufBase::Size()const-aSize).
2. If the new size is smaller than the existing size, the function is equivalent to ExpandL((CBufBase::Size()const,aSize-Size()).
3. The motivations for using CBufBase::ResizeL(TInt) are the same as those for using CBufBase::Delete(TInt,TInt) and CBufBase::ExpandL(TInt,TInt).
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virtual void Compress()=0;
Compresses the buffer so as to occupy minimal space.
Normally, you would call this when a buffer has reached its final size, or when you know it will not expand again for a while, or when an out-of-memory error has occurred and your program is taking measures to save space. Compression in these circumstances releases memory for other programs to use, but has no adverse effect on performance.
Derived classes provide the implementation.
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CBufFlat::Compress()Compresses the buffer so as to occupy minimal space.CBufSeg::Compress()Compresses the buffer so as to occupy minimal space.virtual void Delete(TInt aPos, TInt aLength)=0;
Deletes data from the buffer.
Derived classes provide the implementation.
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CBufFlat::Delete(TInt,TInt)Deletes data from the buffer.CBufSeg::Delete(TInt,TInt)Deletes data from the buffer.virtual TPtr8 Ptr(TInt aPos)=0;
Gets a pointer descriptor to represent the data from the specified position to the end of the contiguous region containing that byte.
Derived classes provide the implementation.
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CBufFlat::Ptr(TInt)Gets a pointer descriptor to represent the data starting at the specified data b...CBufSeg::Ptr(TInt)Gets a pointer descriptor to represent the data starting at the specified data b...virtual TPtr8 BackPtr(TInt aPos)=0;
Gets a pointer descriptor to represent data from just before the specified data byte backward to the beginning of the contiguous region containing that byte.
Derived classes provide the implementation.
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CBufFlat::BackPtr(TInt)Gets a pointer descriptor to represent the data starting at the beginning of the...CBufSeg::BackPtr(TInt)Gets a pointer descriptor to represent the data starting at the beginning of the...private: virtual void DoInsertL(TInt aPos, const TAny *aPtr, TInt aLength)=0;
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protected: TInt iExpandSize;
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Copyright © 2005-2008 Symbian Software Ltd. |
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