class KZoneAllocator

# class KZoneAllocator | Memory allocator for large groups of small objects. More...
Definition | `#include <kallocator.h>`
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#### Public Methods

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

#### Protected Types

- typedef QValueList MemList

#### Protected Methods

- void addBlock (MemBlock *b)
- void delBlock (MemBlock *b)
- void insertHash (MemBlock *b)
- void initHash ()

#### Protected Members

- Forward MemBlock
- MemBlock *currentBlock
- unsigned long blockSize
- unsigned long blockOffset
- unsigned int log2
- unsigned int num_blocks
- MemList **hashList
- unsigned int hashSize
- bool hashDirty

## 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.

KZoneAllocator (unsigned long _blockSize = 8*1024) | ### KZoneAllocator

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.

void* allocate (size_t _size) | ### allocate

Allocates a memory block.

Parameters:

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

void deallocate (void *ptr) | ### deallocate

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 free_since (void *ptr) | ### free_since

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.

typedef QValueList MemList | ### MemList

[protected]

void addBlock (MemBlock *b) | ### addBlock

[protected]

void delBlock (MemBlock *b) | ### delBlock

[protected]

void insertHash (MemBlock *b) | ### insertHash

[protected]

void initHash () | ### initHash

[protected]

MemBlock * currentBlock | ### currentBlock

[protected]

unsigned long blockSize | ### blockSize

[protected]

unsigned long blockOffset | ### blockOffset

[protected]

unsigned int log2 | ### log2

[protected]

unsigned int num_blocks | ### num_blocks

[protected]

MemList ** hashList | ### hashList

[protected]

unsigned int hashSize | ### hashSize

[protected]

bool hashDirty | ### hashDirty

[protected]

- Version: $Id: kallocator.h,v 1.8 2002/09/09 20:22:16 tjansen Exp $
- Author: Waldo Bastian , Michael Matz
- Generated: root on macppc.ports.openbsd.org on Sat Sep 6 10:36:15 2003, using kdoc 2.0a54.