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KZoneAllocator Class Reference

#include <kallocator.h>

List of all members.

Public Methods
	KZoneAllocator (unsigned long _blockSize=8 *1024)
	~KZoneAllocator ()
void *	allocate (size_t _size)
void	deallocate (void *ptr)
void	free_since (void *ptr)

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Detailed Description

Memory allocator for large groups of small objects. This should be used for large groups of objects that are created and destroyed together. When used carefully for this purpose it is faster and more memory efficient than malloc. Additionally to a usual obstack like allocator you can also free the objects individually. Because it does no compaction it still is faster then malloc()/free(). Depending on the exact usage pattern that might come at the expense of some memory though.

Author:

Waldo Bastian <bastian@kde.org>, Michael Matz <matz@kde.org>

Version:

Id:

kallocator.h,v 1.8 2002/09/09 20:22:16 tjansen Exp

Definition at line 47 of file kallocator.h.

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Constructor & Destructor Documentation

KZoneAllocator::KZoneAllocator (  unsigned long    _blockSize = 8 *1024 )

Creates a KZoneAllocator object. Parameters: _blockSize  Size in bytes of the blocks requested from malloc.

KZoneAllocator::~KZoneAllocator (    )

Destructs the ZoneAllocator and free all memory allocated by it.

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Member Function Documentation

void* KZoneAllocator::allocate (  size_t    _size )

Allocates a memory block. Parameters: _size  Size in bytes of the memory block. Memory is aligned to the size of a pointer.

void KZoneAllocator::deallocate (  void *    ptr )

Gives back a block returned by allocate() to the zone allocator, and possibly deallocates the block holding it (when it's empty). The first deallocate() after many allocate() calls (or the first at all) builds an internal data structure for speeding up deallocation. The consistency of that structure is maintained from then on (by allocate() and deallocate()) unless many more objects are allocated without any intervening deallocation, in which case it's thrown away and rebuilt at the next deallocate(). The effect of this is, that such initial deallocate() calls take more time then the normal calls, and that after this list is built, i.e. generally if deallocate() is used at all, also allocate() is a little bit slower. This means, that if you want to squeeze out the last bit performance you would want to use KZoneAllocator as an obstack, i.e. just use the functions allocate() and free_since(). All the remaining memory is returned to the system if the zone allocator is destroyed. Parameters: ptr  Pointer as returned by allocate().

void KZoneAllocator::free_since (  void *    ptr )

Deallocate many objects at once. free_since() deallocates all objects allocated after ptr, including ptr itself. The intended use is something along the lines of: KZoneAllocator alloc(8192); void *remember_me = alloc.allocate(0); for (int i = 0; i < 1000; i++) do_something_with (alloc.allocate(12)); alloc.free_since (remember_me); Note, that we don't need to remember all the pointers to the 12-byte objects for freeing them. The free_since() does deallocate them all at once. Parameters: ptr  Pointer as returned by allocate(). It acts like a kind of mark of a certain position in the stack of all objects, off which you can throw away everything above that mark.

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

• kallocator.h

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