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/*
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* Heap Handler
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*
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* COPYRIGHT (c) 1989-1999.
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* On-Line Applications Research Corporation (OAR).
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.OARcorp.com/rtems/license.html.
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*
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* $Id: heapfree.c,v 1.2 2001-09-27 11:59:34 chris Exp $
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*/
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#include <rtems/system.h>
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#include <rtems/score/sysstate.h>
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#include <rtems/score/heap.h>
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/*PAGE
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*
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* _Heap_Free
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*
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* This kernel routine returns the memory designated by the
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* given heap and given starting address to the memory pool.
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*
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* Input parameters:
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* the_heap - pointer to heap header
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* starting_address - starting address of the memory block to free.
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*
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* Output parameters:
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* TRUE - if starting_address is valid heap address
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* FALSE - if starting_address is invalid heap address
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*/
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boolean _Heap_Free(
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Heap_Control *the_heap,
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void *starting_address
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)
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{
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Heap_Block *the_block;
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Heap_Block *next_block;
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Heap_Block *new_next_block;
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Heap_Block *previous_block;
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Heap_Block *temporary_block;
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unsigned32 the_size;
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the_block = _Heap_User_block_at( starting_address );
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if ( !_Heap_Is_block_in( the_heap, the_block ) ||
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_Heap_Is_block_free( the_block ) ) {
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return( FALSE );
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}
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the_size = _Heap_Block_size( the_block );
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next_block = _Heap_Block_at( the_block, the_size );
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if ( !_Heap_Is_block_in( the_heap, next_block ) ||
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(the_block->front_flag != next_block->back_flag) ) {
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return( FALSE );
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}
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if ( _Heap_Is_previous_block_free( the_block ) ) {
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previous_block = _Heap_Previous_block( the_block );
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if ( !_Heap_Is_block_in( the_heap, previous_block ) ) {
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return( FALSE );
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}
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if ( _Heap_Is_block_free( next_block ) ) { /* coalesce both */
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previous_block->front_flag += next_block->front_flag + the_size;
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temporary_block = _Heap_Next_block( previous_block );
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temporary_block->back_flag = previous_block->front_flag;
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next_block->next->previous = next_block->previous;
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next_block->previous->next = next_block->next;
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}
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else { /* coalesce prev */
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previous_block->front_flag =
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next_block->back_flag = previous_block->front_flag + the_size;
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}
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}
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else if ( _Heap_Is_block_free( next_block ) ) { /* coalesce next */
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the_block->front_flag = the_size + next_block->front_flag;
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new_next_block = _Heap_Next_block( the_block );
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new_next_block->back_flag = the_block->front_flag;
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the_block->next = next_block->next;
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the_block->previous = next_block->previous;
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next_block->previous->next = the_block;
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next_block->next->previous = the_block;
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if (the_heap->first == next_block)
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the_heap->first = the_block;
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}
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else { /* no coalesce */
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next_block->back_flag =
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the_block->front_flag = the_size;
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the_block->previous = _Heap_Head( the_heap );
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the_block->next = the_heap->first;
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the_heap->first = the_block;
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the_block->next->previous = the_block;
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}
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return( TRUE );
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}
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