This group contains the Heap Handler implementation.
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#define | HEAP_PROTECTION_HEADER_SIZE 0 |
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#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).
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#define | HEAP_PREV_BLOCK_USED ((uintptr_t) 1) |
| See also Heap_Block::size_and_flag.
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#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.
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#define | _Heap_Protection_block_initialize(heap, block) ((void) 0) |
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#define | _Heap_Protection_block_check(heap, block) ((void) 0) |
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#define | _Heap_Protection_block_error(heap, block, reason) ((void) 0) |
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#define | _Heap_Protection_free_all_delayed_blocks(heap) ((void) 0) |
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#define | _HAssert(cond) ((void) 0) |
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uintptr_t | _Heap_Extend (Heap_Control *heap, void *area_begin, uintptr_t area_size, uintptr_t unused) |
| Extends the memory available for the heap.
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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.
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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.
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uintptr_t | _Heap_Initialize (Heap_Control *heap, void *area_begin, uintptr_t area_size, uintptr_t page_size) |
| Initializes the heap control block.
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void * | _Heap_Allocate_aligned_with_boundary (Heap_Control *heap, uintptr_t size, uintptr_t alignment, uintptr_t boundary) |
| Allocates an aligned memory area with boundary constraint.
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bool | _Heap_Free (Heap_Control *heap, void *addr) |
| Frees the allocated memory area.
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bool | _Heap_Walk (Heap_Control *heap, int source, bool dump) |
| Verifies the integrity of the heap.
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void | _Heap_Iterate (Heap_Control *heap, Heap_Block_visitor visitor, void *visitor_arg) |
| Iterates over all blocks of the heap.
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Heap_Block * | _Heap_Greedy_allocate (Heap_Control *heap, const uintptr_t *block_sizes, size_t block_count) |
| Greedily allocates and empties the heap.
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Heap_Block * | _Heap_Greedy_allocate_all_except_largest (Heap_Control *heap, uintptr_t *allocatable_size) |
| Greedily allocates all blocks except the largest free block.
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void | _Heap_Greedy_free (Heap_Control *heap, Heap_Block *blocks) |
| Frees blocks of a greedy allocation.
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void | _Heap_Get_information (Heap_Control *heap, Heap_Information_block *info) |
| Returns information about used and free blocks for the heap.
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void | _Heap_Get_free_information (Heap_Control *heap, Heap_Information *info) |
| Returns information about free blocks for the heap.
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bool | _Heap_Size_of_alloc_area (Heap_Control *heap, void *addr, uintptr_t *size) |
| Returns the size of the allocatable memory area.
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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.
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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.
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This group contains the Heap Handler implementation.
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.
◆ 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
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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_Error_reason
The heap error reason.
- See also
- _Heap_Protection_block_error().
Enumerator |
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HEAP_ERROR_BROKEN_PROTECTOR | There is an unexpected value in the heap block protector area.
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HEAP_ERROR_FREE_PATTERN | There is an unexpected value in the free pattern of a free heap block.
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HEAP_ERROR_DOUBLE_FREE | There is was an attempt to free the same block twice.
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HEAP_ERROR_BAD_USED_BLOCK | The next block of a supposed to be used block does not indicate that the block is used.
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HEAP_ERROR_BAD_FREE_BLOCK | A supposed to be free block is not inside the heap memory area.
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◆ _Heap_Allocate_aligned_with_boundary()
void * _Heap_Allocate_aligned_with_boundary |
( |
Heap_Control * |
heap, |
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uintptr_t |
size, |
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uintptr_t |
alignment, |
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uintptr_t |
boundary |
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Allocates an aligned memory area with boundary constraint.
A size value of zero will return a unique address which may be freed with _Heap_Free().
- Parameters
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[in,out] | heap | The heap to allocate a memory are from. |
| size | The size of the desired memory are in bytes. |
| alignment | The allocated memory area will begin at an address aligned by this value. |
| boundary | The allocated memory area will fulfill a boundary constraint, if this value is not equal to zero. 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. |
- Return values
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pointer | The starting address of the allocated memory area. |
NULL | No memory is available of the parameters are inconsistent. |
◆ _Heap_Block_allocate()
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.
- Parameters
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[in,out] | heap | The heap to operate upon. |
| block | The block in which the memory area should be allocated |
| alloc_begin | The starting address of the memory area that shall be allocated. |
| alloc_size | The size of the desired allocated area in bytes. |
- Returns
- The block containing the allocated memory area.
◆ _Heap_Extend()
uintptr_t _Heap_Extend |
( |
Heap_Control * |
heap, |
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void * |
area_begin, |
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uintptr_t |
area_size, |
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uintptr_t |
unused |
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Extends the memory available for the heap.
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.
- Parameters
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[in,out] | heap | The heap to extend. |
[out] | area_begin | The start address of the area to extend the heap with. |
| area_size | The size of the area in bytes. |
| unused | Is not used, only provided to have the same signature as _Heap_Initialize(). |
- Return values
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some_value | The extended space available for allocation after successful extension. |
0 | The heap extension failed. |
- See also
- Heap_Initialization_or_extend_handler.
◆ _Heap_Free()
Frees the allocated memory area.
Inappropriate values for addr may corrupt the heap.
- Parameters
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[in,out] | heap | The heap of the allocated memory area. |
| addr | The starting address of the memory area to be freed. |
- Return values
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true | The allocated memory area was successfully freed. |
false | The method failed. |
◆ _Heap_Get_first_and_last_block()
bool _Heap_Get_first_and_last_block |
( |
uintptr_t |
heap_area_begin, |
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uintptr_t |
heap_area_size, |
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uintptr_t |
page_size, |
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uintptr_t |
min_block_size, |
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Heap_Block ** |
first_block_ptr, |
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Heap_Block ** |
last_block_ptr |
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Gets the first and last block for the heap area.
Nothing will be written to this area.
- Parameters
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| heap_area_begin | The starting address of the heap area. |
| heap_area_size | The size of the heap area. |
| page_size | The page size for the calculation. |
| min_block_size | The minimal block size for the calculation. |
[out] | first_block_ptr | The pointer to the first block in the case of success |
[out] | last_block_ptr | The pointer to the last block in the case of success |
- Return values
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true | The area is big enough. |
false | The area is not big enough. |
◆ _Heap_Get_free_information()
Returns information about free blocks for the heap.
- Parameters
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| heap | The heap to get the information from. |
[out] | info | Stores the information about free blocks of heap after the method call. |
◆ _Heap_Get_information()
Returns information about used and free blocks for the heap.
- Parameters
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| heap | The heap to get the information from. |
[out] | info | Stores the information of the heap after the method call. |
◆ _Heap_Greedy_allocate()
Greedily allocates and empties the heap.
Afterwards, the heap has at most block_count allocatable blocks of sizes specified by block_sizes. All other blocks are used.
- Parameters
-
[in,out] | heap | The heap to operate upon |
| block_sizes | The sizes of the allocatable blocks. Must point to an array with block_count members. |
| block_count | The maximum number of allocatable blocks of sizes specified by @block_sizes. |
- Returns
- Pointer to the first allocated block.
- See also
- _Heap_Greedy_free().
◆ _Heap_Greedy_allocate_all_except_largest()
Greedily allocates 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. All other blocks are used.
- Parameters
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[in,out] | heap | The heap to operate upon. |
[out] | allocatable_size | Stores the size of the largest free block of the heap after the method call. |
- Returns
- Pointer to the first allocated block.
- See also
- _Heap_Greedy_free().
◆ _Heap_Greedy_free()
Frees blocks of a greedy allocation.
- Parameters
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◆ _Heap_Initialize()
uintptr_t _Heap_Initialize |
( |
Heap_Control * |
heap, |
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void * |
area_begin, |
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uintptr_t |
area_size, |
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uintptr_t |
page_size |
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Initializes the heap control block.
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.
- Parameters
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[out] | heap | The heap control block to manage the area. |
| area_begin | The starting address of the area. |
| area_size | The size of the area in bytes. |
| page_size | The page size for the calculation |
- Return values
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some_value | The maximum memory available. |
0 | The initialization failed. |
- See also
- Heap_Initialization_or_extend_handler.
◆ _Heap_Iterate()
Iterates over all blocks of the heap.
- Parameters
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[in,out] | heap | The heap to iterate over. |
| visitor | This will be called for each heap block with the argument visitor_arg. |
[in,out] | visitor_arg | The argument for all calls of visitor. |
◆ _Heap_No_extend()
uintptr_t _Heap_No_extend |
( |
Heap_Control * |
unused_0, |
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void * |
unused_1, |
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uintptr_t |
unused_2, |
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uintptr_t |
unused_3 |
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This function returns always zero.
This function only returns zero and does nothing else.
- Parameters
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unused_0 | This parameter does nothing. |
unused_1 | This parameter does nothing. |
unused_2 | This parameter does nothing. |
unused_3 | This parameter does nothing. |
- See also
- Heap_Initialization_or_extend_handler.
◆ _Heap_Resize_block()
Resizes the block of the allocated memory area.
Inappropriate values for addr may corrupt the heap.
- Parameters
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[in,out] | heap | The heap to operate upon. |
| addr | The starting address of the allocated memory area to be resized. |
| size | The least possible size for the new memory area. Resize may be impossible and depends on the current heap usage. |
[out] | old_size | Stores the size available for allocation in the current block before the resize after the method call. |
[out] | new_size | Stores the size available for allocation in the resized block after the method call. In the case of an unsuccessful resize, zero is returned in this parameter |
- Return values
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HEAP_RESIZE_SUCCESSFUL | The resize was successful. |
HEAP_RESIZE_UNSATISFIED | The least possible size size was too big. Resize not possible. |
HEAP_RESIZE_FATAL_ERROR | The block starting at addr is not part of the heap. |
◆ _Heap_Size_of_alloc_area()
bool _Heap_Size_of_alloc_area |
( |
Heap_Control * |
heap, |
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void * |
addr, |
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uintptr_t * |
size |
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Returns the size of the allocatable memory area.
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.
- Parameters
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| heap | The heap to operate upon. |
| addr | The starting address of the allocatable memory area. |
[out] | size | Stores the size of the allocatable memory area after the method call. |
- Return values
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true | The operation was successful. |
false | The operation was not successful. |
◆ _Heap_Walk()
bool _Heap_Walk |
( |
Heap_Control * |
heap, |
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int |
source, |
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bool |
dump |
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Verifies the integrity of the heap.
Walks the heap to verify its integrity.
- Parameters
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heap | The heap whose integrity is to be verified. |
source | If dump is true , this is used to mark the output lines. |
dump | Indicates whether diagnostic messages will be printed to standard output. |
- Return values
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true | No errors occurred, the heapĀ“s integrity is not violated. |
false | The heap is corrupt. |