TStream, TmemoryStream, x64, VCL, FMX найденные грабли

procedure TStream.ReadBuffer(var Buffer; Count: NativeInt);
var
  LTotalCount,
  LReadCount: NativeInt;
begin
  { Perform a read directly. Most of the time this will succeed
    without the need to go into the WHILE loop. }
  LTotalCount := Read(Buffer, Count);
  { Check if there was an error }
  if LTotalCount < 0 then
    ReadError;
 
  while (LTotalCount < Count) do
  begin
    { Try to read a contiguous block of <Count> size }
    LReadCount := Read(PByte(PByte(@Buffer) + LTotalCount)^,
      (Count - LTotalCount));
 
    { Check if we read something and decrease the number of bytes left to read }
    if LReadCount <= 0 then
      ReadError
    else
      Inc(LTotalCount, LReadCount);
  end
end;

function TStream.Read(var Buffer; Count: Longint): Longint;
begin
  Result := 0;
end;

type
 PBtArr = BtArr^;
 BtArr = TBytes;

FS: TFileStream:
FM: TMemoruDtream;
 
FS := TFileStream.Create('xxx');
FM := TMemoruDtream.Create;
FM.CopyFrom(FS, FS.Size, 100000000);

function TStream.Read(var Buffer; Count: Longint): Longint;
begin
  Result := 0;
end;
 
function TStream.Write(const Buffer; Count: Longint): Longint;
begin
  Result := 0;
end;
 
{$IF Sizeof(LongInt) <> Sizeof(NativeInt)}
function TStream.Read(var Buffer; Count: NativeInt): NativeInt;
var
  LCount,
  LReadCount: NativeInt;
begin
  Result := 0;
  repeat
    LCount := Min(Longint.MaxValue, Count);
    LReadCount := Read((PByte(@Buffer) + Result)^, Longint(LCount));
    Dec(Count, LReadCount);
    Inc(Result, LReadCount);
  until (Count <= 0) or (LCount <> LReadCount);
end;
 
function TStream.Write(const Buffer; Count: NativeInt): NativeInt;
var
  LCount,
  LWriteCount: NativeInt;
begin
  Result := 0;
  repeat
    LCount := Min(Longint.MaxValue, Count);
    LWriteCount := Write((PByte(@Buffer) + Result)^, Longint(LCount));
    Dec(Count, LWriteCount);
    Inc(Result, LWriteCount);
  until (Count <= 0) or (LCount <> LWriteCount);
end;