HeaderlessAllocator Class Reference

(header-less) pool-based heap allocator provides Allocate and Deallocate without requiring in-band headers; this is useful when allocating page-aligned I/O buffers (headers would waste an entire page per buffer) More...

#include <headerless.h>

Collaboration diagram for HeaderlessAllocator:

Classes
class	Impl

Public Member Functions
	HeaderlessAllocator (size_t poolSize)
void	Reset ()
	restore the original state (as if newly constructed). More...
NOTHROW_DECLARE void *	Allocate (size_t size)
void	Deallocate (void *p, size_t size)
	deallocate memory. More...
void	Validate () const
	perform sanity checks; ensure allocator state is consistent. More...

Static Public Attributes
static const size_t	allocationAlignment = 16
static const size_t	minAllocationSize = 128

Private Attributes
shared_ptr< Impl >	impl

Detailed Description

(header-less) pool-based heap allocator provides Allocate and Deallocate without requiring in-band headers; this is useful when allocating page-aligned I/O buffers (headers would waste an entire page per buffer)

policy:

• allocation: first exhaust the freelist, then allocate more
• freelist: address-ordered good fit, always split blocks
• coalescing: immediate mechanism:
• coalescing: boundary tags in freed memory with distinct bit patterns
• freelist: segregated range lists of power-of-two size classes

note: this module basically implements a (rather complex) freelist and could be made independent of the Pool allocation scheme. however, reading neighboring boundary tags may cause segmentation violations; knowing the bounds of valid committed memory (i.e. Pool extents) avoids this.

Constructor & Destructor Documentation

HeaderlessAllocator::HeaderlessAllocator

(

size_t

poolSize

)

Parameters

poolSize

maximum amount of memory that can be allocated. this much virtual address space is reserved up-front (see Pool).

Member Function Documentation

NOTHROW_DEFINE void * HeaderlessAllocator::Allocate

(

size_t

size

)

Parameters

size	[bytes] (= minAllocationSize + i*allocationAlignment). (this allocator is designed for requests on the order of several KiB)

Returns

allocated memory or 0 if the pool is too fragmented or full.

void HeaderlessAllocator::Deallocate	(	void *	p,
		size_t	size
	)

deallocate memory.

Parameters

p	must be exactly as returned by Allocate (in particular, evenly divisible by allocationAlignment)
size	must be exactly as specified to Allocate.

void HeaderlessAllocator::Reset

(

)

restore the original state (as if newly constructed).

this includes reclaiming all extant allocations.

void HeaderlessAllocator::Validate

(

)

const

perform sanity checks; ensure allocator state is consistent.

Member Data Documentation

const size_t HeaderlessAllocator::allocationAlignment = 16

static

shared_ptr<Impl> HeaderlessAllocator::impl

private

const size_t HeaderlessAllocator::minAllocationSize = 128

static

---

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

• /var/svn/checkout/source/lib/allocators/headerless.h
• /var/svn/checkout/source/lib/allocators/headerless.cpp