class PAbstractArray

This class contains a variable length array of arbitrary memory blocks.

Inheritance:


Public Methods

[more] Construction
[more] Overrides from class PObject
[more] Overrides from class PContainer
[more] New functions for class

Protected Fields

[more]PINDEX elementSize
Size of an element in bytes
[more]char* theArray
Pointer to the allocated block of memory
[more]BOOL allocatedDynamically
Flag indicating the array was allocated on the heap


Inherited from PContainer:

Public Methods

Common functions for containers

Protected Methods

ovirtual void DestroyContents()
ovirtual void AssignContents(const PContainer & c)
ovoid CopyContents(const PContainer & c)
ovoid CloneContents(const PContainer* src)
ovoid Destruct()


Inherited from PObject:

Public Methods

Run Time Type functions

I/O functions

Public Members

Comparison functions


Documentation

This class contains a variable length array of arbitrary memory blocks. These can be anything from individual bytes to large structures. Note that that does not include class objects that require construction or destruction. Elements in this array will not execute the contructors or destructors of objects.

An abstract array consists of a linear block of memory sufficient to hold PContainer::GetSize() elements of elementSize bytes each. The memory block itself will atuomatically be resized when required and freed when no more references to it are present.

The PAbstractArray class would very rarely be descended from directly by the user. The PBASEARRAY macro would normally be used to create a class and any new classes descended from that. That will instantiate the template based on PBaseArray or directly declare and define a class (using inline functions) if templates are not being used.

The PBaseArray class or PBASEARRAY macro will define the correctly typed operators for pointer access (operator const T *) and subscript access (operator[]).

o Construction

o PAbstractArray( PINDEX elementSizeInBytes, PINDEX initialSize = 0 )
Create a new dynamic array of initalSize elements of elementSizeInBytes bytes each. The array memory is initialised to zeros.

If the initial size is zero then no memory is allocated. Note that the internal pointer is set to NULL, not to a pointer to zero bytes of memory. This can be an important distinction when the pointer is obtained via an operator created in the PBASEARRAY macro.

Parameters:
elementSizeInBytes - Size of each element in the array. This must be > 0 or the constructor will assert.
initialSize - Number of elements to allocate initially.

o PAbstractArray( PINDEX elementSizeInBytes, const void* buffer, PINDEX bufferSizeInElements, BOOL dynamicAllocation )
Create a new dynamic array of bufferSizeInElements elements of elementSizeInBytes bytes each. The contents of the memory pointed to by buffer is then used to initialise the newly allocated array.

If the initial size is zero then no memory is allocated. Note that the internal pointer is set to NULL, not to a pointer to zero bytes of memory. This can be an important distinction when the pointer is obtained via an operator created in the PBASEARRAY macro.

If the dynamicAllocation parameter is FALSE then the pointer is used directly by the container. It will not be copied to a dynamically allocated buffer. If the SetSize() function is used to change the size of the buffer, the object will be converted to a dynamic form with the contents of the static buffer copied to the allocated buffer.

Parameters:
elementSizeInBytes - Size of each element in the array. This must be > 0 or the constructor will assert.
- buffer Pointer to an array of elements.
bufferSizeInElements - Number of elements pointed to by buffer.
dynamicAllocation - Buffer is copied and dynamically allocated.

o Overrides from class PObject

ovirtual void PrintOn( ostream &strm ) const
Output the contents of the object to the stream. The exact output is dependent on the exact semantics of the descendent class. This is primarily used by the standard operator<< function.

The default behaviour is to print the class name.

ovirtual void ReadFrom( istream &strm )
Input the contents of the object from the stream. The exact input is dependent on the exact semantics of the descendent class. This is primarily used by the standard operator>> function.

The default behaviour is to do nothing.

ovirtual Comparison Compare( const PObject & obj ) const
Get the relative rank of the two arrays. The following algorithm is employed for the comparison:
EqualTo
if the two array memory blocks are identical in length and contents.
LessThan
if the array length is less than the obj parameters array length.
GreaterThan
if the array length is greater than the obj parameters array length.

If the array sizes are identical then the memcmp() function is used to rank the two arrays.

Parameters:
obj - Other PAbstractArray to compare against.
Returns:
comparison of the two objects, EqualTo for same, LessThan for obj logically less than the object and GreaterThan for obj logically greater than the object.

o Overrides from class PContainer

ovirtual BOOL SetSize( PINDEX newSize )
Set the size of the array in elements. A new array may be allocated to accomodate the new number of elements. If the array increases in size then the new bytes are initialised to zero. If the array is made smaller then the data beyond the new size is lost.

Parameters:
newSize - New size of the array in elements.
Returns:
TRUE if the memory for the array was allocated successfully.

o New functions for class

ovoid Attach( const void* buffer, PINDEX bufferSize )
Attach a pointer to a static block to the base array type. The pointer is used directly and will not be copied to a dynamically allocated buffer. If the SetSize() function is used to change the size of the buffer, the object will be converted to a dynamic form with the contents of the static buffer copied to the allocated buffer.

Any dynamically allocated buffer will be freed.

Parameters:
- buffer Pointer to an array of elements.
- bufferSize Number of elements pointed to by buffer.

ovoid* GetPointer( PINDEX minSize = 1 )
Get a pointer to the internal array and assure that it is of at least the specified size. This is useful when the array contents are being set by some external or system function eg file read.

It is unsafe to assume that the pointer is valid for very long after return from this function. The array may be resized or otherwise changed and the pointer returned invalidated. It should be used for simple calls to atomic functions, or very careful examination of the program logic must be performed.

Parameters:
minSize - Minimum size the array must be.
Returns:
pointer to the array memory.

oBOOL Concatenate( const PAbstractArray & array )
Concatenate one array to the end of this array. This function will allocate a new array large enough for the existing contents and the contents of the parameter. The paramters contents is then copied to the end of the existing array.

Note this does nothing and returns FALSE if the target array is not dynamically allocated, or if the two arrays are of base elements of different sizes.

Parameters:
array - Array to concatenate.
Returns:
TRUE if the memory allocation succeeded.

oPINDEX elementSize
Size of an element in bytes

ochar* theArray
Pointer to the allocated block of memory

oBOOL allocatedDynamically
Flag indicating the array was allocated on the heap


Direct child classes:
PBaseArray
Friends:
class PArrayObjects

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