NCollection_AccAllocator Class Reference

Class NCollection_AccAllocator - accumulating memory allocator. This class allocates memory on request returning the pointer to the allocated space. The allocation units are grouped in blocks requested from the system as required. This memory is returned to the system when all allocations in a block are freed. More...

#include <NCollection_AccAllocator.hxx>

Inheritance diagram for NCollection_AccAllocator:

Data Structures
class	AlignedPtr
	A pointer aligned to a 4 byte boundary. More...
class	AlignedSize
	Size value aligned to a 4 byte boundary. More...
struct	Block
	Descriptor of a block. More...
class	Hasher
	Key hasher. More...
struct	Key
	A key for the map of blocks. More...

Public Member Functions
	NCollection_AccAllocator (const size_t theBlockSize=DefaultBlockSize)
	Constructor.
	~NCollection_AccAllocator ()
	Destructor.
virtual void *	Allocate (const size_t theSize) override
	Allocate memory with given size.
void *	AllocateOptimal (const size_t theSize) override
	Allocate memory with given size.
virtual void	Free (void *theAddress) override
	Free a previously allocated memory; memory is returned to the OS when all allocations in some block are freed.
Public Member Functions inherited from Standard_Transient
	Standard_Transient ()
	Empty constructor.
	Standard_Transient (const Standard_Transient &)
	Copy constructor – does nothing.
Standard_Transient &	operator= (const Standard_Transient &)
	Assignment operator, needed to avoid copying reference counter.
virtual	~Standard_Transient ()
	Destructor must be virtual.
virtual const opencascade::handle< Standard_Type > &	DynamicType () const
	Returns a type descriptor about this object.
Standard_Boolean	IsInstance (const opencascade::handle< Standard_Type > &theType) const
	Returns a true value if this is an instance of Type.
Standard_Boolean	IsInstance (const Standard_CString theTypeName) const
	Returns a true value if this is an instance of TypeName.
Standard_Boolean	IsKind (const opencascade::handle< Standard_Type > &theType) const
	Returns true if this is an instance of Type or an instance of any class that inherits from Type. Note that multiple inheritance is not supported by OCCT RTTI mechanism.
Standard_Boolean	IsKind (const Standard_CString theTypeName) const
	Returns true if this is an instance of TypeName or an instance of any class that inherits from TypeName. Note that multiple inheritance is not supported by OCCT RTTI mechanism.
Standard_Transient *	This () const
	Returns non-const pointer to this object (like const_cast). For protection against creating handle to objects allocated in stack or call from constructor, it will raise exception Standard_ProgramError if reference counter is zero.
Standard_Integer	GetRefCount () const noexcept
	Get the reference counter of this object.
void	IncrementRefCounter () noexcept
	Increments the reference counter of this object.
Standard_Integer	DecrementRefCounter () noexcept
	Decrements the reference counter of this object; returns the decremented value.
virtual void	Delete () const
	Memory deallocator for transient classes.

Static Public Attributes
static const Standard_Size	Align = 4
	Alignment of all allocated objects: 4 bytes.
static const Standard_Size	DefaultBlockSize = 24600
	Default block size.
static const Standard_Integer	MaxLookupBlocks = 16
	Number of last blocks to check for free space.

Protected Member Functions
Key	getKey (const Standard_Address theAddress) const
	Calculate a key for the data map basing on the given address.
Block *	findBlock (const Standard_Address theAddress, Key &theKey)
	Find a block that the given allocation unit belongs to.
Block *	allocateNewBlock (const Standard_Size theSize)
	Allocate a new block and return a pointer to it.
Protected Member Functions inherited from NCollection_BaseAllocator
	NCollection_BaseAllocator ()
	Constructor - prohibited.

Protected Attributes
AlignedSize	myBlockSize
Block *	mypLastBlock
NCollection_DataMap< Key, Block, Hasher >	myBlocks

Additional Inherited Members
Public Types inherited from Standard_Transient
typedef void	base_type
	Returns a type descriptor about this object.
Static Public Member Functions inherited from NCollection_BaseAllocator
static const Handle< NCollection_BaseAllocator > &	CommonBaseAllocator (void)
	CommonBaseAllocator This method is designed to have the only one BaseAllocator (to avoid useless copying of collections). However one can use operator new to create more BaseAllocators, but it is injurious.
Static Public Member Functions inherited from Standard_Transient
static constexpr const char *	get_type_name ()
	Returns a type descriptor about this object.
static const opencascade::handle< Standard_Type > &	get_type_descriptor ()
	Returns type descriptor of Standard_Transient class.

Detailed Description

Class NCollection_AccAllocator - accumulating memory allocator. This class allocates memory on request returning the pointer to the allocated space. The allocation units are grouped in blocks requested from the system as required. This memory is returned to the system when all allocations in a block are freed.

By comparison with the standard new() and malloc() calls, this method is faster and consumes very small additional memory to maintain the heap.

By comparison with NCollection_IncAllocator, this class requires some more additional memory and a little more time for allocation and deallocation. Memory overhead for NCollection_IncAllocator is 12 bytes per block; average memory overhead for NCollection_AccAllocator is 28 bytes per block.

All pointers returned by Allocate() are aligned to 4 byte boundaries. To define the size of memory blocks requested from the OS, use the parameter of the constructor (measured in bytes).

Constructor & Destructor Documentation

NCollection_AccAllocator()

NCollection_AccAllocator::NCollection_AccAllocator

(

const size_t

theBlockSize = DefaultBlockSize

)

Constructor.

~NCollection_AccAllocator()

NCollection_AccAllocator::~NCollection_AccAllocator

(

)

Destructor.

Member Function Documentation

Allocate()

virtual void * NCollection_AccAllocator::Allocate ( const size_t  theSize )

overridevirtual

Allocate memory with given size.

Reimplemented from NCollection_BaseAllocator.

allocateNewBlock()

Block * NCollection_AccAllocator::allocateNewBlock ( const Standard_Size  theSize )

protected

Allocate a new block and return a pointer to it.

AllocateOptimal()

void * NCollection_AccAllocator::AllocateOptimal ( const size_t  theSize )

inlineoverridevirtual

Allocate memory with given size.

Reimplemented from NCollection_BaseAllocator.

findBlock()

Block * NCollection_AccAllocator::findBlock ( const Standard_Address  theAddress, Key &  theKey  )

protected

Find a block that the given allocation unit belongs to.

Free()

virtual void NCollection_AccAllocator::Free ( void *  theAddress )

overridevirtual

Free a previously allocated memory; memory is returned to the OS when all allocations in some block are freed.

Reimplemented from NCollection_BaseAllocator.

getKey()

Key NCollection_AccAllocator::getKey ( const Standard_Address  theAddress ) const

inlineprotected

Calculate a key for the data map basing on the given address.

Field Documentation

Align

const Standard_Size NCollection_AccAllocator::Align = 4

static

Alignment of all allocated objects: 4 bytes.

DefaultBlockSize

const Standard_Size NCollection_AccAllocator::DefaultBlockSize = 24600

static

Default block size.

MaxLookupBlocks

const Standard_Integer NCollection_AccAllocator::MaxLookupBlocks = 16

static

Number of last blocks to check for free space.

myBlocks

NCollection_DataMap<Key, Block, Hasher> NCollection_AccAllocator::myBlocks

protected

myBlockSize

AlignedSize NCollection_AccAllocator::myBlockSize

protected

mypLastBlock

Block* NCollection_AccAllocator::mypLastBlock

protected

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The documentation for this class was generated from the following file:

• NCollection_AccAllocator.hxx