问GetMem、指针和访问冲突

EN

Exception EAccessViolation: Access violation at address 0040AA1F in module
'UMTester.exe'. Write of address 00000069 (OS Exception)  Exception occurred at
$0040AA1F (Module "System", Procedure "@DynArrayAsg", Unit "", Line 0)

constructor TFactory.Create(FactoryObjectClass : tclass;Capacity : integer);
var nn : integer;
fptr : pointer;
fObj : TFactoryObject;
begin
  fClass := FactoryObjectClass;
  fsize := fclass.InstanceSize;
  fdata:=nil;

  //Capacity represents the number of objects; trying to allocate small amounts 
  //of memory results in exceptions so i artificially increase it anything less 
  //than 20 throws an exception
  if Capacity<19 then Capacity:=20;

  //This seems to reduce exceptions as the requested memory is in whole blocks 
  while frac((Capacity*SizeOf(Pointer))/4)<>0.0 do Inc(Capacity);

  fcapacity := Capacity;

  //Allocate memory
  getmem(fdata,fsize*fcapacity);
  getmem(fDatalist,sizeof(Pointer)*fcapacity);
  getmem(ffreelist,sizeof(Pointer)*fcapacity);

  fdatacount :=0;
  ffreecount :=0;
  fptr       := fdata;

  //create a pointer to the factory object at each memory address
  for nn := 0 to Capacity-1 do begin
   fdatalist[fdatacount]:= fptr;         <------- Exception is always here
   fobj := Fclass.InitInstance(fptr) as TFactoryObject;
   fobj.factory := self;
   fObj.Create;
   fptr := pointer(integer(fptr)+fsize);
   inc(fDataCount);
  end;
end;

  procedure TObjs.Initialize(AObjs : TDict);
  var
   nn :integer;
   C : TRttiContext;
   T : TRttiInstanceType;
   V : TValue;
  begin
    //Process all objects requested
    for nn := 0 to AObjs.Count-1 do begin
      //Locate the class from the supplied reference in AObjs
      T := (C.GetType(TClass(FindClass(AObjs[nn]['Type']))) as TRttiInstanceType);

      //Invoke the creation of the object by calling its native constructor
      V := T.GetMethod('Create').Invoke(T.metaClassType,[Application]);

      //Adds each requested object to the repository and displays the object
      Objs[nn].SetValue(V.AsObject,AObjs[nn]);
    end;
  end;

  SetLength(Objs,AObjs.Count);
  AFactory := TFactory.Create(TchObj,AObjs.Count);

  //Initialize the full array of objects
  for Index := 0 to AObjs.Count -1 do
    Objs[Index] := Afactory.Request_obj as TchObj;

  TchFactory = class
    private
      fdata      : pointer;
      fsize      : integer;
      fDataList  : PPointerList;  // from classes unit
      fdatacount : integer;
      fFreeList  : PPointerList;
      fFreeCount : integer;
      fCapacity  : integer;
      fcLass     : TClass;
    public
      constructor Create(FactoryObjectClass : Tclass;Capacity : integer);
      destructor  Destroy;   override;
      function    Request_Obj : TchFactoryObject;
      procedure   Recycle(FactoryObject : TchFactoryObject);
    property Capacity  : integer read fCapacity;
    property CountUsed : integer read fdataCount;
    property CountFree : integer read fFreeCount;
  end;

constructor TchFactory.Create(FactoryObjectClass : tclass;Capacity : integer);
  var Index : integer;
  fptr : pointer;
  fObj : TchFactoryObject;
  begin
    fClass := FactoryObjectClass;
    fsize := fclass.InstanceSize;

    fcapacity := Capacity;
    fdata := AllocMem(fsize*fcapacity);
    fdatalist:= AllocMem(sizeof(Pointer)*fcapacity);
    fFreelist:= AllocMem(sizeof(Pointer)*fcapacity);
    fdatacount :=0;
    ffreecount :=0;
    fptr       := fdata;

    for index := 0 to Capacity-1 do begin

      fdatalist[fdatacount]:= fptr;
      fobj := Fclass.InitInstance(fptr) as TchFactoryObject;
      fobj.factory := self;
      fObj.Create;
      fptr := pointer(integer(fptr)+fsize);
      inc(fDataCount);

     end;      
  end;