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/*
* Heap Handler
*
* COPYRIGHT (c) 1989-2009.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/system.h>
#include <rtems/score/heap.h>
static uint32_t instance = 0;
/*PAGE
*
* _Heap_Initialize
*
* This kernel routine initializes a heap.
*
* Input parameters:
* heap - pointer to heap header
* area_begin - starting address of heap
* size - size of heap
* page_size - allocatable unit of memory
*
* Output parameters:
* returns - maximum memory available if RTEMS_SUCCESSFUL
* 0 - otherwise
*
* This is what a heap looks like in memory immediately after initialization:
*
*
* +--------------------------------+ <- begin = area_begin
* | unused space due to alignment |
* | size < page_size |
* 0 +--------------------------------+ <- first block
* | prev_size = page_size |
* 4 +--------------------------------+
* | size = size0 | 1 |
* 8 +---------------------+----------+ <- aligned on page_size
* | next = HEAP_TAIL | |
* 12 +---------------------+ |
* | prev = HEAP_HEAD | memory |
* +---------------------+ |
* | available |
* | |
* | for allocation |
* | |
* size0 +--------------------------------+ <- last dummy block
* | prev_size = size0 |
* +4 +--------------------------------+
* | size = page_size | 0 | <- prev block is free
* +8 +--------------------------------+ <- aligned on page_size
* | unused space due to alignment |
* | size < page_size |
* +--------------------------------+ <- end = begin + size
*
* Below is what a heap looks like after first allocation of SIZE bytes using
* _Heap_allocate(). BSIZE stands for SIZE + 4 aligned up on 'page_size'
* boundary.
* [NOTE: If allocation were performed by _Heap_Allocate_aligned(), the
* block size BSIZE is defined differently, and previously free block will
* be split so that upper part of it will become used block (see
* 'heapallocatealigned.c' for details).]
*
* +--------------------------------+ <- begin = area_begin
* | unused space due to alignment |
* | size < page_size |
* 0 +--------------------------------+ <- used block
* | prev_size = page_size |
* 4 +--------------------------------+
* | size = BSIZE | 1 | <- prev block is used
* 8 +--------------------------------+ <- aligned on page_size
* | . | Pointer returned to the user
* | . | is 8 for _Heap_Allocate()
* | . | and is in range
* 8 + | user-accessible | [8,8+page_size) for
* page_size +- - - - - -+ _Heap_Allocate_aligned()
* | area |
* | . |
* BSIZE +- - - - - . - - - - -+ <- free block
* | . |
* BSIZE +4 +--------------------------------+
* | size = S = size0 - BSIZE | 1 | <- prev block is used
* BSIZE +8 +-------------------+------------+ <- aligned on page_size
* | next = HEAP_TAIL | |
* BSIZE +12 +-------------------+ |
* | prev = HEAP_HEAD | memory |
* +-------------------+ |
* | . available |
* | . |
* | . for |
* | . |
* BSIZE +S+0 +-------------------+ allocation + <- last dummy block
* | prev_size = S | |
* +S+4 +-------------------+------------+
* | size = page_size | 0 | <- prev block is free
* +S+8 +--------------------------------+ <- aligned on page_size
* | unused space due to alignment |
* | size < page_size |
* +--------------------------------+ <- end = begin + size
*
*/
uintptr_t _Heap_Initialize(
Heap_Control *heap,
void *area_begin,
uintptr_t area_size,
uintptr_t page_size
)
{
Heap_Statistics * const stats = &heap->stats;
uintptr_t heap_area_begin = (uintptr_t) area_begin;
uintptr_t heap_area_end = heap_area_begin + area_size;
uintptr_t alloc_area_begin = heap_area_begin + HEAP_BLOCK_ALLOC_AREA_OFFSET;
uintptr_t alloc_area_size = 0;
uintptr_t overhead = 0;
Heap_Block *first_block = NULL;
Heap_Block *second_block = NULL;
if ( page_size == 0 ) {
page_size = CPU_ALIGNMENT;
} else {
page_size = _Heap_Align_up( page_size, CPU_ALIGNMENT );
}
heap->min_block_size = _Heap_Align_up( sizeof( Heap_Block ), page_size );
alloc_area_begin = _Heap_Align_up( alloc_area_begin, page_size );
overhead = HEAP_LAST_BLOCK_OVERHEAD
+ (alloc_area_begin - HEAP_BLOCK_ALLOC_AREA_OFFSET - heap_area_begin);
alloc_area_size = _Heap_Align_down ( area_size - overhead, page_size );
if (
heap_area_end < heap_area_begin
|| area_size < overhead
|| alloc_area_size == 0
) {
/* Invalid area or area too small */
return 0;
}
heap->page_size = page_size;
heap->begin = heap_area_begin;
heap->end = heap_area_end;
/* First block */
first_block = _Heap_Block_of_alloc_area( alloc_area_begin, page_size );
first_block->prev_size = page_size;
first_block->size_and_flag = alloc_area_size | HEAP_PREV_BLOCK_USED;
first_block->next = _Heap_Free_list_tail( heap );
first_block->prev = _Heap_Free_list_head( heap );
_Heap_Free_list_head( heap )->next = first_block;
_Heap_Free_list_tail( heap )->prev = first_block;
heap->start = first_block;
/* Second and last block */
second_block = _Heap_Block_at( first_block, alloc_area_size );
second_block->prev_size = alloc_area_size;
second_block->size_and_flag = page_size | HEAP_PREV_BLOCK_FREE;
heap->final = second_block;
/* Statistics */
stats->size = area_size;
stats->free_size = alloc_area_size;
stats->min_free_size = alloc_area_size;
stats->free_blocks = 1;
stats->max_free_blocks = 1;
stats->used_blocks = 0;
stats->max_search = 0;
stats->allocs = 0;
stats->searches = 0;
stats->frees = 0;
stats->resizes = 0;
stats->instance = instance++;
_HAssert( _Heap_Is_aligned( CPU_ALIGNMENT, 4 ));
_HAssert( _Heap_Is_aligned( heap->page_size, CPU_ALIGNMENT ));
_HAssert( _Heap_Is_aligned( heap->min_block_size, page_size ));
_HAssert(
_Heap_Is_aligned( _Heap_Alloc_area_of_block( first_block ), page_size )
);
_HAssert(
_Heap_Is_aligned( _Heap_Alloc_area_of_block( second_block ), page_size )
);
return alloc_area_size;
}
uintptr_t _Heap_Calc_block_size(
uintptr_t alloc_size,
uintptr_t page_size,
uintptr_t min_block_size)
{
uintptr_t block_size =
_Heap_Align_up( alloc_size + HEAP_BLOCK_USED_OVERHEAD, page_size );
if (block_size < min_block_size) {
block_size = min_block_size;
}
if (block_size > alloc_size) {
return block_size;
} else {
/* Integer overflow occured */
return 0;
}
}
uintptr_t _Heap_Block_allocate(
Heap_Control *heap,
Heap_Block *block,
uintptr_t alloc_size
)
{
Heap_Statistics * const stats = &heap->stats;
uintptr_t const block_size = _Heap_Block_size( block );
uintptr_t const unused_size = block_size - alloc_size;
Heap_Block *next_block = _Heap_Block_at( block, block_size );
_HAssert( _Heap_Is_aligned( block_size, heap->page_size ));
_HAssert( _Heap_Is_aligned( alloc_size, heap->page_size ));
_HAssert( alloc_size <= block_size );
_HAssert( _Heap_Is_prev_used( block ));
if (unused_size >= heap->min_block_size) {
/*
* Split the block so that the upper part is still free, and the lower part
* becomes used. This is slightly less optimal than leaving the lower part
* free as it requires replacing block in the free blocks list, but it
* makes it possible to reuse this code in the _Heap_Resize_block().
*/
Heap_Block *new_block = _Heap_Block_at( block, alloc_size );
block->size_and_flag = alloc_size | HEAP_PREV_BLOCK_USED;
new_block->size_and_flag = unused_size | HEAP_PREV_BLOCK_USED;
next_block->prev_size = unused_size;
_Heap_Block_replace_in_free_list( block, new_block );
} else {
next_block->size_and_flag |= HEAP_PREV_BLOCK_USED;
alloc_size = block_size;
_Heap_Block_remove_from_free_list( block );
/* Statistics */
--stats->free_blocks;
}
/* Statistics */
++stats->used_blocks;
stats->free_size -= alloc_size;
if(stats->min_free_size > stats->free_size) {
stats->min_free_size = stats->free_size;
}
return alloc_size;
}
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