The Heap Handler provides a heap. More...

Modules
	Protected Heap Handler
	Provides protected heap services.

Files
file	heap.h
	Heap Handler API.

file	heapimpl.h
	Heap Handler Implementation.

file	heapinfo.h
	Heap Handler Information API.

file	heap.c
	Heap Handler implementation.

file	heapallocate.c
	Heap Handler implementation.

file	heapextend.c
	Heap Handler implementation.

file	heapfree.c
	Heap Handler implementation.

file	heapgetfreeinfo.c
	Heap Handler implementation.

file	heapgetinfo.c
	Heap Handler implementation.

file	heapgreedy.c
	Heap Handler API.

file	heapiterate.c
	_Heap_Iterate() implementation.

file	heapnoextend.c
	Heap Handler implementation.

file	heapresizeblock.c
	Heap Handler implementation.

file	heapsizeofuserarea.c
	Heap Handler implementation.

file	heapwalk.c
	Heap Handler implementation.

Data Structures
struct	Heap_Block
	Description for free or used blocks. More...

struct	Heap_Control
	Control block used to manage a heap. More...

struct	Heap_Area
	Heap area structure for table based heap initialization and extension. More...

struct	Heap_Statistics
	Run-time heap statistics. More...

struct	Heap_Information
	Information about blocks. More...

struct	Heap_Information_block
	Information block returned by _Heap_Get_information(). More...

Macros
#define	HEAP_PROTECTION_HEADER_SIZE 0

#define	HEAP_BLOCK_HEADER_SIZE (2 * sizeof(uintptr_t) + HEAP_PROTECTION_HEADER_SIZE)
	The block header consists of the two size fields (Heap_Block::prev_size and Heap_Block::size_and_flag).

#define	HEAP_PREV_BLOCK_USED ((uintptr_t) 1)
	See also Heap_Block::size_and_flag.

#define	HEAP_ALLOC_BONUS sizeof(uintptr_t)
	Size of the part at the block begin which may be used for allocation in charge of the previous block.

#define	_Heap_Protection_block_initialize(heap, block) ((void) 0)

#define	_Heap_Protection_block_check(heap, block) ((void) 0)

#define	_Heap_Protection_block_error(heap, block) ((void) 0)

#define	_Heap_Protection_free_all_delayed_blocks(heap) ((void) 0)

#define	_HAssert(cond) ((void) 0)

Typedefs
typedef struct Heap_Control	Heap_Control

typedef struct Heap_Block	Heap_Block

typedef uintptr_t(*	Heap_Initialization_or_extend_handler) (Heap_Control heap, void area_begin, uintptr_t area_size, uintptr_t page_size_or_unused)
	Heap initialization and extend handler type. More...

typedef bool(*	Heap_Block_visitor) (const Heap_Block block, uintptr_t block_size, bool block_is_used, void visitor_arg)
	Heap block visitor. More...

Enumerations
enum	Heap_Resize_status { HEAP_RESIZE_SUCCESSFUL, HEAP_RESIZE_UNSATISFIED, HEAP_RESIZE_FATAL_ERROR }
	See _Heap_Resize_block().

Functions
uintptr_t	_Heap_Extend (Heap_Control heap, void area_begin, uintptr_t area_size, uintptr_t unused)
	Extends the memory available for the heap heap using the memory area starting at area_begin of size area_size bytes. More...

uintptr_t	_Heap_No_extend (Heap_Control unused_0, void unused_1, uintptr_t unused_2, uintptr_t unused_3)
	This function returns always zero. More...

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Align_up (uintptr_t value, uintptr_t alignment)

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Min_block_size (uintptr_t page_size)

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Area_overhead (uintptr_t page_size)
	Returns the worst case overhead to manage a memory area.

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Size_with_overhead (uintptr_t page_size, uintptr_t size, uintptr_t alignment)
	Returns the size with administration and alignment overhead for one allocation.

bool	_Heap_Get_first_and_last_block (uintptr_t heap_area_begin, uintptr_t heap_area_size, uintptr_t page_size, uintptr_t min_block_size, Heap_Block first_block_ptr, Heap_Block last_block_ptr)
	Gets the first and last block for the heap area with begin heap_area_begin and size heap_area_size. More...

uintptr_t	_Heap_Initialize (Heap_Control heap, void area_begin, uintptr_t area_size, uintptr_t page_size)
	Initializes the heap control block heap to manage the area starting at area_begin of size area_size bytes. More...

void *	_Heap_Allocate_aligned_with_boundary (Heap_Control *heap, uintptr_t size, uintptr_t alignment, uintptr_t boundary)
	Allocates a memory area of size size bytes from the heap heap. More...

RTEMS_INLINE_ROUTINE void *	_Heap_Allocate_aligned (Heap_Control *heap, uintptr_t size, uintptr_t alignment)
	See _Heap_Allocate_aligned_with_boundary() with boundary equals zero.

RTEMS_INLINE_ROUTINE void *	_Heap_Allocate (Heap_Control *heap, uintptr_t size)
	See _Heap_Allocate_aligned_with_boundary() with alignment and boundary equals zero.

bool	_Heap_Free (Heap_Control heap, void addr)
	Frees the allocated memory area starting at addr in the heap heap. More...

bool	_Heap_Walk (Heap_Control *heap, int source, bool dump)
	Walks the heap heap to verify its integrity. More...

void	_Heap_Iterate (Heap_Control heap, Heap_Block_visitor visitor, void visitor_arg)
	Iterates over all blocks of the heap. More...

Heap_Block *	_Heap_Greedy_allocate (Heap_Control heap, const uintptr_t block_sizes, size_t block_count)
	Greedy allocate that empties the heap. More...

Heap_Block *	_Heap_Greedy_allocate_all_except_largest (Heap_Control heap, uintptr_t allocatable_size)
	Greedy allocate all blocks except the largest free block. More...

void	_Heap_Greedy_free (Heap_Control heap, Heap_Block blocks)
	Frees blocks of a greedy allocation. More...

void	_Heap_Get_information (Heap_Control heap, Heap_Information_block info)
	Returns information about used and free blocks for the heap heap in info.

void	_Heap_Get_free_information (Heap_Control heap, Heap_Information info)
	Returns information about free blocks for the heap heap in info.

bool	_Heap_Size_of_alloc_area (Heap_Control heap, void addr, uintptr_t *size)
	Returns the size of the allocatable memory area starting at addr in size. More...

Heap_Resize_status	_Heap_Resize_block (Heap_Control heap, void addr, uintptr_t size, uintptr_t old_size, uintptr_t new_size)
	Resizes the block of the allocated memory area starting at addr. More...

Heap_Block *	_Heap_Block_allocate (Heap_Control heap, Heap_Block block, uintptr_t alloc_begin, uintptr_t alloc_size)
	Allocates the memory area starting at alloc_begin of size alloc_size bytes in the block block. More...

RTEMS_INLINE_ROUTINE void	_Heap_Protection_set_delayed_free_fraction (Heap_Control *heap, uintptr_t fraction)
	Sets the fraction of delayed free blocks that is actually freed during memory shortage. More...

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Free_list_head (Heap_Control *heap)

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Free_list_tail (Heap_Control *heap)

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Free_list_first (Heap_Control *heap)

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Free_list_last (Heap_Control *heap)

RTEMS_INLINE_ROUTINE void	_Heap_Free_list_remove (Heap_Block *block)

RTEMS_INLINE_ROUTINE void	_Heap_Free_list_replace (Heap_Block old_block, Heap_Block new_block)

RTEMS_INLINE_ROUTINE void	_Heap_Free_list_insert_after (Heap_Block block_before, Heap_Block new_block)

RTEMS_INLINE_ROUTINE void	_Heap_Free_list_insert_before (Heap_Block block_next, Heap_Block new_block)

RTEMS_INLINE_ROUTINE bool	_Heap_Is_aligned (uintptr_t value, uintptr_t alignment)

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Align_down (uintptr_t value, uintptr_t alignment)

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Block_at (const Heap_Block *block, uintptr_t offset)
	Returns the block which is offset away from block.

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Prev_block (const Heap_Block *block)

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Alloc_area_of_block (const Heap_Block *block)

RTEMS_INLINE_ROUTINE Heap_Block *	_Heap_Block_of_alloc_area (uintptr_t alloc_begin, uintptr_t page_size)

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Block_size (const Heap_Block *block)

RTEMS_INLINE_ROUTINE void	_Heap_Block_set_size (Heap_Block *block, uintptr_t size)

RTEMS_INLINE_ROUTINE bool	_Heap_Is_prev_used (const Heap_Block *block)

RTEMS_INLINE_ROUTINE bool	_Heap_Is_used (const Heap_Block *block)

RTEMS_INLINE_ROUTINE bool	_Heap_Is_free (const Heap_Block *block)

RTEMS_INLINE_ROUTINE bool	_Heap_Is_block_in_heap (const Heap_Control heap, const Heap_Block block)

RTEMS_INLINE_ROUTINE void	_Heap_Set_last_block_size (Heap_Control *heap)
	Sets the size of the last block for heap heap. More...

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Get_size (const Heap_Control *heap)
	Returns the size of the allocatable area in bytes. More...

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Max (uintptr_t a, uintptr_t b)

RTEMS_INLINE_ROUTINE uintptr_t	_Heap_Min (uintptr_t a, uintptr_t b)

Detailed Description

The Heap Handler provides a heap.

A heap is a doubly linked list of variable size blocks which are allocated using the first fit method. Garbage collection is performed each time a block is returned to the heap by coalescing neighbor blocks. Control information for both allocated and free blocks is contained in the heap area. A heap control structure contains control information for the heap.

The alignment routines could be made faster should we require only powers of two to be supported for page size, alignment and boundary arguments. The minimum alignment requirement for pages is currently CPU_ALIGNMENT and this value is only required to be multiple of two and explicitly not required to be a power of two.

There are two kinds of blocks. One sort describes a free block from which we can allocate memory. The other blocks are used and provide an allocated memory area. The free blocks are accessible via a list of free blocks.

Blocks or areas cover a continuous set of memory addresses. They have a begin and end address. The end address is not part of the set. The size of a block or area equals the distance between the begin and end address in units of bytes.

Free blocks look like:

Heap_Block	previous block size in case the previous block is free, otherwise it may contain data used by the previous block
	block size and a flag which indicates if the previous block is free or used, this field contains always valid data regardless of the block usage
	pointer to next block (this field is page size aligned)
	pointer to previous block
free space

Used blocks look like:

Heap_Block	previous block size in case the previous block is free, otherwise it may contain data used by the previous block
	block size and a flag which indicates if the previous block is free or used, this field contains always valid data regardless of the block usage
	begin of allocated area (this field is page size aligned)
	allocated space
allocated space

The heap area after initialization contains two blocks and looks like:

Label	Content
heap->area_begin	heap area begin address
first_block->prev_size	subordinate heap area end address (this will be used to maintain a linked list of scattered heap areas)
first_block->size	size available for allocation \| `HEAP_PREV_BLOCK_USED`
first_block->next	_Heap_Free_list_tail(heap)	memory area available for allocation
first_block->prev	_Heap_Free_list_head(heap)
...
last_block->prev_size	size of first block
last_block->size	first block begin address - last block begin address
heap->area_end	heap area end address

The next block of the last block is the first block. Since the first block indicates that the previous block is used, this ensures that the last block appears as used for the _Heap_Is_used() and _Heap_Is_free() functions.

Typedef Documentation

◆ Heap_Block_visitor

typedef bool(* Heap_Block_visitor) (const Heap_Block *block, uintptr_t block_size, bool block_is_used, void *visitor_arg)

Heap block visitor.

See also: _Heap_Iterate().

Return values

true	Stop the iteration.
false	Continue the iteration.

◆ Heap_Initialization_or_extend_handler

typedef uintptr_t(* Heap_Initialization_or_extend_handler) (Heap_Control *heap, void *area_begin, uintptr_t area_size, uintptr_t page_size_or_unused)

Heap initialization and extend handler type.

This helps to do a table based heap initialization and extension. Create a table of Heap_Area elements and iterate through it. Set the handler to _Heap_Initialize() in the first iteration and then to _Heap_Extend().

See also: Heap_Area, _Heap_Initialize(), _Heap_Extend(), or _Heap_No_extend().

Function Documentation

◆ _Heap_Allocate_aligned_with_boundary()

void* _Heap_Allocate_aligned_with_boundary	(	Heap_Control *	heap,
		uintptr_t	size,
		uintptr_t	alignment,
		uintptr_t	boundary
	)

Allocates a memory area of size size bytes from the heap heap.

If the alignment parameter alignment is not equal to zero, the allocated memory area will begin at an address aligned by this value.

If the boundary parameter boundary is not equal to zero, the allocated memory area will fulfill a boundary constraint. The boundary value specifies the set of addresses which are aligned by the boundary value. The interior of the allocated memory area will not contain an element of this set. The begin or end address of the area may be a member of the set.

A size value of zero will return a unique address which may be freed with _Heap_Free().

Returns a pointer to the begin of the allocated memory area, or NULL if no memory is available or the parameters are inconsistent.

◆ _Heap_Block_allocate()

Heap_Block* _Heap_Block_allocate	(	Heap_Control *	heap,
		Heap_Block *	block,
		uintptr_t	alloc_begin,
		uintptr_t	alloc_size
	)

Allocates the memory area starting at alloc_begin of size alloc_size bytes in the block block.

The block may be split up into multiple blocks. The previous and next block may be used or free. Free block parts which form a vaild new block will be inserted into the free list or merged with an adjacent free block. If the block is used, they will be inserted after the free list head. If the block is free, they will be inserted after the previous block in the free list.

Inappropriate values for alloc_begin or alloc_size may corrupt the heap.

Returns the block containing the allocated memory area.

◆ _Heap_Extend()

uintptr_t _Heap_Extend	(	Heap_Control *	heap,
		void *	area_begin,
		uintptr_t	area_size,
		uintptr_t	unused
	)

Extends the memory available for the heap heap using the memory area starting at area_begin of size area_size bytes.

There are no alignment requirements for the memory area. The memory area must be big enough to contain some maintenance blocks. It must not overlap parts of the current heap memory areas. Disconnected memory areas added to the heap will lead to used blocks which cover the gaps. Extending with an inappropriate memory area will corrupt the heap resulting in undefined behaviour.

The unused fourth parameter is provided to have the same signature as _Heap_Initialize().

Returns the extended space available for allocation, or zero in case of failure.

See also: Heap_Initialization_or_extend_handler.

◆ _Heap_Free()

bool _Heap_Free	(	Heap_Control *	heap,
		void *	addr
	)

Frees the allocated memory area starting at addr in the heap heap.

Inappropriate values for addr may corrupt the heap.

Returns true in case of success, and false otherwise.

◆ _Heap_Get_first_and_last_block()

bool _Heap_Get_first_and_last_block	(	uintptr_t	heap_area_begin,
		uintptr_t	heap_area_size,
		uintptr_t	page_size,
		uintptr_t	min_block_size,
		Heap_Block **	first_block_ptr,
		Heap_Block **	last_block_ptr
	)

Gets the first and last block for the heap area with begin heap_area_begin and size heap_area_size.

A page size of page_size and minimal block size of min_block_size will be used for calculation.

Nothing will be written to this area.

In case of success the pointers to the first and last block will be returned via first_block_ptr and last_block_ptr.

Returns true if the area is big enough, and false otherwise.

◆ _Heap_Get_size()

RTEMS_INLINE_ROUTINE uintptr_t _Heap_Get_size ( const Heap_Control * heap )

Returns the size of the allocatable area in bytes.

This value is an integral multiple of the page size.

◆ _Heap_Greedy_allocate()

Heap_Block* _Heap_Greedy_allocate	(	Heap_Control *	heap,
		const uintptr_t *	block_sizes,
		size_t	block_count
	)

Greedy allocate that empties the heap.

Afterwards the heap has at most block_count allocatable blocks of sizes specified by block_sizes. The block_sizes must point to an array with block_count members. All other blocks are used.

See also: _Heap_Greedy_free().

◆ _Heap_Greedy_allocate_all_except_largest()

Heap_Block* _Heap_Greedy_allocate_all_except_largest	(	Heap_Control *	heap,
		uintptr_t *	allocatable_size
	)

Greedy allocate all blocks except the largest free block.

Afterwards the heap has at most one allocatable block. This block is the largest free block if it exists. The allocatable size of this block is stored in allocatable_size. All other blocks are used.

See also: _Heap_Greedy_free().

◆ _Heap_Greedy_free()

void _Heap_Greedy_free	(	Heap_Control *	heap,
		Heap_Block *	blocks
	)

Frees blocks of a greedy allocation.

The blocks must be the return value of _Heap_Greedy_allocate().

◆ _Heap_Initialize()

uintptr_t _Heap_Initialize	(	Heap_Control *	heap,
		void *	area_begin,
		uintptr_t	area_size,
		uintptr_t	page_size
	)

Initializes the heap control block heap to manage the area starting at area_begin of size area_size bytes.

Blocks of memory are allocated from the heap in multiples of page_size byte units. If the page_size is equal to zero or is not multiple of CPU_ALIGNMENT, it is aligned up to the nearest CPU_ALIGNMENT boundary.

Returns the maximum memory available, or zero in case of failure.

See also: Heap_Initialization_or_extend_handler.

◆ _Heap_Iterate()

void _Heap_Iterate	(	Heap_Control *	heap,
		Heap_Block_visitor	visitor,
		void *	visitor_arg
	)

Iterates over all blocks of the heap.

For each block the visitor with the argument visitor_arg will be called.

◆ _Heap_No_extend()

uintptr_t _Heap_No_extend	(	Heap_Control *	unused_0,
		void *	unused_1,
		uintptr_t	unused_2,
		uintptr_t	unused_3
	)

This function returns always zero.

This function only returns zero and does nothing else.

Returns always zero.

See also: Heap_Initialization_or_extend_handler.

◆ _Heap_Protection_set_delayed_free_fraction()

RTEMS_INLINE_ROUTINE void _Heap_Protection_set_delayed_free_fraction	(	Heap_Control *	heap,
		uintptr_t	fraction
	)

Sets the fraction of delayed free blocks that is actually freed during memory shortage.

The default is to free half the delayed free blocks. This is equal to a fraction value of two.

Parameters

[in]	heap	The heap control.
[in]	fraction	The fraction is one divided by this fraction value.

◆ _Heap_Resize_block()

Heap_Resize_status _Heap_Resize_block	(	Heap_Control *	heap,
		void *	addr,
		uintptr_t	size,
		uintptr_t *	old_size,
		uintptr_t *	new_size
	)

Resizes the block of the allocated memory area starting at addr.

The new memory area will have a size of at least size bytes. A resize may be impossible and depends on the current heap usage.

The size available for allocation in the current block before the resize will be returned in old_size. The size available for allocation in the resized block will be returned in new_size. If the resize was not successful, then a value of zero will be returned in new_size.

Inappropriate values for addr may corrupt the heap.

◆ _Heap_Set_last_block_size()

RTEMS_INLINE_ROUTINE void _Heap_Set_last_block_size ( Heap_Control * heap )

Sets the size of the last block for heap heap.

The next block of the last block will be the first block. Since the first block indicates that the previous block is used, this ensures that the last block appears as used for the _Heap_Is_used() and _Heap_Is_free() functions.

This feature will be used to terminate the scattered heap area list. See also _Heap_Extend().

◆ _Heap_Size_of_alloc_area()

bool _Heap_Size_of_alloc_area	(	Heap_Control *	heap,
		void *	addr,
		uintptr_t *	size
	)

Returns the size of the allocatable memory area starting at addr in size.

The size value may be greater than the initially requested size in _Heap_Allocate_aligned_with_boundary().

Inappropriate values for addr will not corrupt the heap, but may yield invalid size values.

Returns true if successful, and false otherwise.

◆ _Heap_Walk()

bool _Heap_Walk	(	Heap_Control *	heap,
		int	source,
		bool	dump
	)

Walks the heap heap to verify its integrity.

If dump is true, then diagnostic messages will be printed to standard output. In this case source is used to mark the output lines.

Returns true if no errors occurred, and false if the heap is corrupt.

Modules

Files

Data Structures

Macros

Typedefs

Enumerations

Functions