Open CASCADE Technology  7.3.1.dev
Data Structures | Public Member Functions | Static Public Attributes | Protected Member Functions | Protected Attributes
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:
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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. More...
 
 ~NCollection_AccAllocator ()
 Destructor. More...
 
virtual void * Allocate (const size_t theSize) override
 Allocate memory with given size. More...
 
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. More...
 
- Public Member Functions inherited from Standard_Transient
 Standard_Transient ()
 Empty constructor. More...
 
 Standard_Transient (const Standard_Transient &)
 Copy constructor – does nothing. More...
 
Standard_Transientoperator= (const Standard_Transient &)
 Assignment operator, needed to avoid copying reference counter. More...
 
virtual ~Standard_Transient ()
 Destructor must be virtual. More...
 
virtual void Delete () const
 Memory deallocator for transient classes. More...
 
virtual const opencascade::handle< Standard_Type > & DynamicType () const
 Returns a type descriptor about this object. More...
 
Standard_Boolean IsInstance (const opencascade::handle< Standard_Type > &theType) const
 Returns a true value if this is an instance of Type. More...
 
Standard_Boolean IsInstance (const Standard_CString theTypeName) const
 Returns a true value if this is an instance of TypeName. More...
 
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. More...
 
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. More...
 
Standard_TransientThis () 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. More...
 
Standard_Integer GetRefCount () const
 Get the reference counter of this object. More...
 
void IncrementRefCounter () const
 Increments the reference counter of this object. More...
 
Standard_Integer DecrementRefCounter () const
 Decrements the reference counter of this object; returns the decremented value. More...
 

Static Public Attributes

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

Protected Member Functions

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

Protected Attributes

AlignedSize myBlockSize
 
BlockmypLastBlock
 
NCollection_DataMap< Key, Block, HashermyBlocks
 

Additional Inherited Members

- Public Types inherited from Standard_Transient
typedef void base_type
 Returns a type descriptor about this object. More...
 
- 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. More...
 
static void StandardCallBack (const Standard_Boolean theIsAlloc, const Standard_Address theStorage, const Standard_Size theRoundSize, const Standard_Size theSize)
 Callback function to register alloc/free calls. More...
 
static void PrintMemUsageStatistics ()
 Prints memory usage statistics cumulated by StandardCallBack. More...
 
- Static Public Member Functions inherited from Standard_Transient
static const char * get_type_name ()
 Returns a type descriptor about this object. More...
 
static const opencascade::handle< Standard_Type > & get_type_descriptor ()
 Returns type descriptor of Standard_Transient class. More...
 

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.

◆ 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

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