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Diffstat (limited to 'cpukit/score/src/heapresizeblock.c')
| -rw-r--r-- | cpukit/score/src/heapresizeblock.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/cpukit/score/src/heapresizeblock.c b/cpukit/score/src/heapresizeblock.c new file mode 100644 index 0000000000..661ef20b51 --- /dev/null +++ b/cpukit/score/src/heapresizeblock.c @@ -0,0 +1,170 @@ +/* + * Heap Handler + * + * COPYRIGHT (c) 1989-1999. + * 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. + * + * $Id$ + */ + + +#include <rtems/system.h> +#include <rtems/score/sysstate.h> +#include <rtems/score/heap.h> + +/* + * _Heap_Resize_block + * + * DESCRIPTION: + * + * This routine tries to resize in place the block that is pointed to by the + * 'starting_address' to the new 'size'. + * + * Input parameters: + * the_heap - pointer to heap header + * starting_address - starting address of the memory block + * size - new size + * + * Output parameters: + * 'old_mem_size' - the size of the user memory area of the block before + * resizing. + * 'avail_mem_size' - the size of the user memory area of the free block + * that has been enlarged or created due to resizing, + * 0 if none. + * Returns + * HEAP_RESIZE_SUCCESSFUL - if success + * HEAP_RESIZE_UNSATISFIED - if the block can't be resized in place + * HEAP_RESIZE_FATAL_ERROR - if failure + */ + +Heap_Resize_status _Heap_Resize_block( + Heap_Control *the_heap, + void *starting_address, + uint32_t size, + uint32_t *old_mem_size, + uint32_t *avail_mem_size +) +{ + Heap_Block *the_block; + Heap_Block *next_block; + uint32_t next_block_size; + boolean next_is_used; + Heap_Block *next_next_block; + uint32_t old_block_size; + uint32_t old_user_size; + uint32_t prev_used_flag; + Heap_Statistics *const stats = &the_heap->stats; + uint32_t const min_block_size = the_heap->min_block_size; + uint32_t const page_size = the_heap->page_size; + + *old_mem_size = 0; + *avail_mem_size = 0; + + _Heap_Start_of_block(the_heap, starting_address, &the_block); + _HAssert(_Heap_Is_block_in(the_heap, the_block)); + if (!_Heap_Is_block_in(the_heap, the_block)) + return HEAP_RESIZE_FATAL_ERROR; + + prev_used_flag = the_block->size & HEAP_PREV_USED; + old_block_size = _Heap_Block_size(the_block); + next_block = _Heap_Block_at(the_block, old_block_size); + + _HAssert(_Heap_Is_block_in(the_heap, next_block)); + _HAssert(_Heap_Is_prev_used(next_block)); + if ( !_Heap_Is_block_in(the_heap, next_block) || + !_Heap_Is_prev_used(next_block)) + return HEAP_RESIZE_FATAL_ERROR; + + next_block_size = _Heap_Block_size(next_block); + next_next_block = _Heap_Block_at(next_block, next_block_size); + next_is_used = (next_block == the_heap->final) || + _Heap_Is_prev_used(next_next_block); + + /* See _Heap_Size_of_user_area() source for explanations */ + old_user_size = _Addresses_Subtract(next_block, starting_address) + + HEAP_BLOCK_HEADER_OFFSET; + + *old_mem_size = old_user_size; + + if (size > old_user_size) { + /* Need to extend the block: allocate part of the next block and then + merge 'the_block' and allocated block together. */ + if (next_is_used) /* Next block is in use, -- no way to extend */ + return HEAP_RESIZE_UNSATISFIED; + else { + uint32_t add_block_size = size - old_user_size; + _Heap_Align_up(&add_block_size, page_size); + if (add_block_size < min_block_size) + add_block_size = min_block_size; + if (add_block_size > next_block_size) + return HEAP_RESIZE_UNSATISFIED; /* Next block is too small or none. */ + add_block_size = + _Heap_Block_allocate(the_heap, next_block, add_block_size); + /* Merge two subsequent blocks */ + the_block->size = (old_block_size + add_block_size) | prev_used_flag; + --stats->used_blocks; + } + } else { + + /* Calculate how much memory we could free */ + uint32_t free_block_size = old_user_size - size; + _Heap_Align_down(&free_block_size, page_size); + + if (free_block_size > 0) { + + /* To free some memory the block should be shortened so that it can + can hold 'size' user bytes and still remain not shorter than + 'min_block_size'. */ + + uint32_t new_block_size = old_block_size - free_block_size; + + if (new_block_size < min_block_size) { + uint32_t delta = min_block_size - new_block_size; + _HAssert(free_block_size >= delta); + free_block_size -= delta; + if (free_block_size == 0) { + ++stats->resizes; + return HEAP_RESIZE_SUCCESSFUL; + } + new_block_size += delta; + } + + _HAssert(new_block_size >= min_block_size); + _HAssert(new_block_size + free_block_size == old_block_size); + _HAssert(_Heap_Is_aligned(new_block_size, page_size)); + _HAssert(_Heap_Is_aligned(free_block_size, page_size)); + + if (!next_is_used) { + /* Extend the next block to the low addresses by 'free_block_size' */ + Heap_Block *const new_next_block = + _Heap_Block_at(the_block, new_block_size); + uint32_t const new_next_block_size = + next_block_size + free_block_size; + _HAssert(_Heap_Is_block_in(the_heap, next_next_block)); + the_block->size = new_block_size | prev_used_flag; + new_next_block->size = new_next_block_size | HEAP_PREV_USED; + next_next_block->prev_size = new_next_block_size; + _Heap_Block_replace(next_block, new_next_block); + the_heap->stats.free_size += free_block_size; + *avail_mem_size = new_next_block_size - HEAP_BLOCK_USED_OVERHEAD; + + } else if (free_block_size >= min_block_size) { + /* Split the block into 2 used parts, then free the second one. */ + the_block->size = new_block_size | prev_used_flag; + next_block = _Heap_Block_at(the_block, new_block_size); + next_block->size = free_block_size | HEAP_PREV_USED; + ++stats->used_blocks; /* We have created used block */ + --stats->frees; /* Don't count next call in stats */ + _Heap_Free(the_heap, _Heap_User_area(next_block)); + *avail_mem_size = free_block_size - HEAP_BLOCK_USED_OVERHEAD; + } + } + } + + ++stats->resizes; + return HEAP_RESIZE_SUCCESSFUL; +} |