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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: heapextend.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_Extend

 *

 *  This routine grows the_heap memory area using the size bytes which

 *  begin at starting_address.

 *

 *  Input parameters:

 *    the_heap          - pointer to heap header.

 *    starting_address  - pointer to the memory area.

 *    size              - size in bytes of the memory block to allocate.

 *

 *  Output parameters:

 *    *amount_extended  - amount of memory added to the_heap

 */

Heap_Extend_status _Heap_Extend(

  Heap_Control        *the_heap,

  void                *starting_address,

  unsigned32           size,

  unsigned32          *amount_extended

)

{

  Heap_Block        *the_block;

  unsigned32        *p;

  /*

   *  The overhead was taken from the original heap memory.

   */

  Heap_Block  *old_final;

  Heap_Block  *new_final;

  /*

   *  There are five possibilities for the location of starting

   *  address:

   *

   *    1. non-contiguous lower address     (NOT SUPPORTED)

   *    2. contiguous lower address         (NOT SUPPORTED)

   *    3. in the heap                      (ERROR)

   *    4. contiguous higher address        (SUPPORTED)

   *    5. non-contiguous higher address    (NOT SUPPORTED)

   *

   *  As noted, this code only supports (4).

   */

  if ( starting_address >= (void *) the_heap->start &&        /* case 3 */

       starting_address <= (void *) the_heap->final

     )

    return HEAP_EXTEND_ERROR;

  if ( starting_address < (void *) the_heap->start ) {  /* cases 1 and 2 */

      return HEAP_EXTEND_NOT_IMPLEMENTED;               /* cases 1 and 2 */

  } else {                                              /* cases 4 and 5 */

    the_block = (Heap_Block *)

       _Addresses_Subtract_offset( starting_address, HEAP_OVERHEAD );

    if ( the_block != the_heap->final )

      return HEAP_EXTEND_NOT_IMPLEMENTED;                   /* case 5 */

  }

  /*

   *  Currently only case 4 should make it to this point.

   *  The basic trick is to make the extend area look like a used

   *  block and free it.

   */

  *amount_extended = size;

  old_final = the_heap->final;

  new_final = _Addresses_Add_offset( old_final, size );

  /* SAME AS: _Addresses_Add_offset( starting_address, size-HEAP_OVERHEAD ); */

  the_heap->final = new_final;

  old_final->front_flag =

  new_final->back_flag  = _Heap_Build_flag( size, HEAP_BLOCK_USED );

  new_final->front_flag = HEAP_DUMMY_FLAG;

  /*

   *  Must pass in address of "user" area

   *  So add in the offset field.

   */

  p = (unsigned32 *) &old_final->next;

  *p = sizeof(unsigned32);

  p++;

  _Heap_Free( the_heap, p );

  return HEAP_EXTEND_SUCCESSFUL;

}