Link to home
Start Free TrialLog in
Avatar of LMuadDIb
LMuadDIbFlag for United States of America

asked on

change a procedure from loading a TFilename to use a TStringList

this procedure decodes a binary tFilename, and I want to create basically the same procedure but to work on a TStringList instead of saving/loading the file from the hard drive which I have to do now. Im not going to put the whole procedure in here.. but try to place parts of it... parts I think I need to adjust.


      AssignFile(InputFile,FInputFilename);
      try
        Reset(InputFile,1);
      except
        raise EyDecoder.Create(Format(DecFileNotFound,[FInputFilename]));
      end;

      InputBlockNo:=0;
      InputFileSize:=System.FileSize(InputFile);

      if Assigned(FOnProgress) then
        begin
          Abort:=False;
          FOnProgress(Self,0,Abort);
          if Abort then
            begin
              if ifopen then CloseFile(InputFile); ifopen:=false;
              FreeMem(InputBuf);
              FreeMem(OutputBuf);
              Exit;
            end;
        end;

      Escaped:=False;
      FindNextKeyword:=True;
      Repeat
        // read a chunk of data
        BlockRead(InputFile,InputBuf^,InputBufferSize,numRead);
        Inc(InputBlockNo);

        DebugMessage(Format('read %d bytes, fp@%d',[numRead,FilePos(InputFile)]));

        P:=InputBuf;
        if numRead=0 then
          begin
            DebugMessage(Format('eof detected, bailing',[]));
            break; // bail out if EOF
          end;

        EndBuf:=PByte(Integer(InputBuf)+numRead-1);
        // find the first escape character

    //    P:=nil;
        DebugMessage(Format('enter decode loop',[]));
        Repeat
          if FindNextKeyword then ....

I can post the whole procedure if needed, or link to the source
any help would be appreciated
Avatar of LMuadDIb
LMuadDIb
Flag of United States of America image

ASKER

actually not a TFilename but it uses File
example:
InputFile,OutputFile: File;

so I guess its pure binary files
but I would still like to use a TStringList , because thats how I recieve the data from the internet.
ASKER CERTIFIED SOLUTION
Avatar of House_of_Dexter
House_of_Dexter
Flag of United States of America image

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
something like this should work...


var
  a_MemStream: TStream;

begin
  a_MemStream := TMemoryStream.Create  
  try
     aStrings.SaveStream(a_MemStream);
    //work with the Stream here...
 
  SaveStream(a_MemStream, MySaveDirectory + MyFileName);
end;

procedure SaveStream(aStream: TStream; aSaveFileName: string);
var
  a_SaveStream: TStream;
begin
{aSaveFileName is a Filename which includes the directory}
   a_SaveStream := TFileStream.Create('aSaveFileName');
   try
     if Assigned(aStream) and Assigned(a_SaveStream) then
        a_SaveStream.CopyFrom(aStream , 0);
  finally
    a_SaveStream.Free;
  end;

end;

House_of_Dexter, Im not sure we are on the same page

I need away to change the above procedure to accept a tstringlist as an arg instead of a TFile.
I dont want to save anything to my drive, I want to do everything in memory with a tstringlist, once its decoded I will save it to my drive

Avatar of Wim ten Brink
House_of_Dexter is correct. Create a Memorystream, which resides in memory and not on disk. Load the stringlist into the memorystream, go back to the beginning of the memory stream and then read from the memorystream the blocks that you want to read.
You will have to adjust your code to use streams instead of files, though.

But since you already have your data inside a stringlist, why not simply use the stringlist functionality instead? I think you're making things way too complex here. It's like getting a square peg into a round hole. You can do that with plenty of force and a big hammer and other tools, but it's easier to just take a round peg instead. ;-)
Like Alex said...once you move over to a MemoryStream...It will act like your buffer...you can move through it just like an Array of Bytes...its a lot easier to do...no need to derefernce the pointer...just move to the byte and read it...

StringList...has a nice functions that will allow you to move your StringList to a MemoryStream...then TStream which   allows you to save the results to disk...in TFileStream...
ok, it will be a couple days before I try this out