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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [exec/] [score/] [src/] [heap.c] - Rev 593
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/* * 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.OARcorp.com/rtems/license.html. * * $Id: heap.c,v 1.2 2001-09-27 11:59:34 chris Exp $ */ #include <rtems/system.h> #include <rtems/score/sysstate.h> #include <rtems/score/heap.h> /*PAGE * * _Heap_Initialize * * This kernel routine initializes a heap. * * Input parameters: * the_heap - pointer to heap header * starting_address - 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: * * +--------------------------------+ * 0 | size = 0 | status = used | a.k.a. dummy back flag * +--------------------------------+ * 4 | size = size-8 | status = free | a.k.a. front flag * +--------------------------------+ * 8 | next = PERM HEAP_TAIL | * +--------------------------------+ * 12 | previous = PERM HEAP_HEAD | * +--------------------------------+ * | | * | memory available | * | for allocation | * | | * +--------------------------------+ * size - 8 | size = size-8 | status = free | a.k.a. back flag * +--------------------------------+ * size - 4 | size = 0 | status = used | a.k.a. dummy front flag * +--------------------------------+ */ unsigned32 _Heap_Initialize( Heap_Control *the_heap, void *starting_address, unsigned32 size, unsigned32 page_size ) { Heap_Block *the_block; unsigned32 the_size; if ( !_Heap_Is_page_size_valid( page_size ) || (size < HEAP_MINIMUM_SIZE) ) return 0; the_heap->page_size = page_size; the_size = size - HEAP_OVERHEAD; the_block = (Heap_Block *) starting_address; the_block->back_flag = HEAP_DUMMY_FLAG; the_block->front_flag = the_size; the_block->next = _Heap_Tail( the_heap ); the_block->previous = _Heap_Head( the_heap ); the_heap->start = the_block; the_heap->first = the_block; the_heap->permanent_null = NULL; the_heap->last = the_block; the_block = _Heap_Next_block( the_block ); the_block->back_flag = the_size; the_block->front_flag = HEAP_DUMMY_FLAG; the_heap->final = the_block; return ( the_size - HEAP_BLOCK_USED_OVERHEAD ); }
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