Frage zum Buffer eines Streams

[sirius]

Hmm..ich weis nicht, was du mit den ganzen parts so machst.
Bevor ich da durchsehe und das auseinanderbaue, habe ich mal versucht, deine Absicht in einer anderen Klasse niederzuschreiben.
(Allein, der Sinn fehlt mir noch, aber egal)

Delphi-Quellcode:

unit Unit2;

interface

uses classes;

type tBufferStream=class(TStream)
         constructor create(const OpenFromFileName:string;TempDirectory:string); reintroduce;
         destructor Destroy; override;
       private
         FMemory:TStream;
         TempDir,TempFile:string;
         swapsize:integer;
       protected
         procedure SetSize(NewSize: Longint); override;
       public
         function Read(var Buffer; Count: Longint): Longint; override;
         function Write(const Buffer; Count: Longint): Longint; override;
         function Seek(Offset: Longint; Origin: Word): Longint; override;
end;



implementation

uses sysutils;

function GetTempFileName(TempDirectory:String):string;
var filename:string;
    i:integer;
begin
i:=0;
filename:=inttostr(i)+'.part';
while fileexists(TempDirectory+filename) do
begin
  inc(i);
  filename:=inttostr(i)+'.part';
end;
result:=TempDirectory+filename;
end;


constructor TBufferStream.create(const OpenFromFileName:string;TempDirectory:string);
var f:Tfilestream;
begin

  TempDir:=TempDirectory;

  swapsize:=5*1024;

  if openfromfilename<>'' then
  begin
    f:=Tfilestream.Create(OpenFromFileName,fmopenread);
    if f.size>swapsize then FMemory:=TFilestream.Create(gettempfilename(tempdir),fmcreate)
                       else Fmemory:=TMemoryStream.Create;
    Fmemory.CopyFrom(f,f.size);
    f.free;
  end else Fmemory:=nil;



end;

function Tbufferstream.Write(const Buffer;Count: Longint): Longint;
var tmp:TStream;
begin
  if Fmemory=nil then Fmemory:=Tmemorystream.Create;
  if (Fmemory is TMemoryStream) and
     (Fmemory.Size+count>swapsize) then
  begin
    tempfile:=gettempfilename(tempdir);
    tmp:=TfileStream.Create(tempfile,fmcreate);
    Fmemory.Seek(0,sofrombeginning);
    tmp.CopyFrom(Fmemory,fmemory.size);
    Fmemory.Free;
    FMemory:=tmp;
  end;
  result:=Fmemory.Write(buffer,count)
end;
function TBufferStream.read(var Buffer;Count: Longint): Longint;
begin
  result:=FMemory.Read(buffer,count);
end;
function TbufferStream.Seek(Offset: Longint; Origin: Word): Longint;
begin
  result:=Fmemory.Seek(offset,origin);
end;

procedure Tbufferstream.SetSize(Newsize:longint);
var tmp:TStream;
begin
  if FMemory=nil then Fmemory:=Tmemorystream.Create;

  Fmemory.Size:=newsize;
  if (newsize<swapsize*2/3) and
      (Fmemory is TFilestream) then
  begin
    tmp:=Tmemorystream.Create;
    Fmemory.Seek(0,sofrombeginning);
    tmp.CopyFrom(FMemory,newsize);
    fmemory.Free;
    fmemory:=tmp;
    deletefile(tempfile);
  end;

  if (newsize>swapsize) and
      (Fmemory is TMemorystream) then
  begin
    tempfile:=gettempfilename(tempdir);
    tmp:=TFilestream.Create(tempfile,fmcreate);
    Fmemory.Seek(0,sofrombeginning);
    tmp.CopyFrom(FMemory,newsize);
    fmemory.Free;
    fmemory:=tmp;
  end;

end;

destructor TbufferStream.Destroy;
begin
  if Fmemory<>nil then
  begin
    if FMemory is TFileStream then
    begin
      Fmemory.Free;
      deletefile(TempFile);
    end
    else Fmemory.Free;
  end;
end;

end.

Jetzt ist mir auch übrigens klar, was deine Eingangsfrage war. Wenn der Buffer untypisiert ist, dann musst du eben auch ganz untypisiert rangehen:

Delphi-Quellcode:

var buffer:pointer;
begin
  GetMem(Buffer,10);
  Stream.ReadBuffer(Buffer^,10);
  //...

  FreeMem(Buffer,10);
end;