unit ASCIIInsert;

interface

   uses CarrierFile, DataFile, Classes
{$IFDEF CLX}
   ,QForms
{$ELSE}
   ,Forms
{$ENDIF}
   ;

   type
     TASCIIInsert = class(TCarrierFile)
   public
     constructor Create; override;
     destructor Destroy; override;
     function GetAvailSize: Longint; virtual;
     function CreateFromCarrierFile(cf: TCarrierFile): Boolean; virtual;
     function ExportToCarrierFile(cf: TCarrierFile): Boolean; virtual;
     function EnoughSpaceToHide(n: Longint): Boolean; virtual;
     function Encode(ToHide: TDataFile): Boolean; virtual;
     function Decode(ResultFile: TDataFile): Boolean; virtual;
   end;

implementation

   constructor TASCIIInsert.Create;
   begin
     inherited Create;
   end;

   destructor TASCIIInsert.Destroy;
   begin
     inherited Create;
   end;

   function TASCIIInsert.GetAvailSize: Longint;
   var
     Buffer:      Array[0..1023] of Byte;
     BytesRead:   Integer;
     LineFeeds:   Integer;
     i:           Integer;
     LFFound:     Boolean;
     p:           Integer;
     Cancel:      Boolean;
   begin
     inherited GetAvailSize;
     Cancel:=False;
     LineFeeds:=0;
     LFFound:=False;
     BytesRead:=1024;
     Data.Seek(0,soFromBeginning);
     p:=Trunc(Data.Size/1024);
     if Assigned(FPercentChange) then FPercentChange(self,Percent);
     Application.ProcessMessages;
     while (BytesRead=1024) and not(Cancel) do begin
       BytesRead:=Data.Read(Buffer,1024);
       for i:=0 to BytesRead-1 do begin
         if ((Buffer[i]=$0d) or (Buffer[i]=$0a)) then begin
           if not(LFFound) then begin
             Inc(LineFeeds);
             if (Buffer[i]=$0d) then LFFound:=True;
           end
           else LFFound:=False;
         end
         else LFFound:=False;
       end;
       Percent:=Percent+p;
       if Assigned(FPercentChange) then FPercentChange(self,Percent);
       if Assigned(FWantCancel) then FWantCancel(self,Cancel);
       Application.ProcessMessages;
     end;
     Percent:=100;
     if Assigned(FPercentChange) then FPercentChange(self,Percent);
     Application.ProcessMessages;
     GetAvailSize:=LineFeeds;
   end;

   function TASCIIInsert.CreateFromCarrierFile(cf: TCarrierFile): Boolean;
   begin
     if cf.GetFileType='TXT' then begin
       Data.Clear;
       cf.SaveToStream(Data);
       SetFileType(cf.GetFileType,cf.GetColorDepth);
       Percent:=cf.Percent;
       CreateFromCarrierFile:=True;
     end
     else CreateFromCarrierFile:=False;
   end;

   function TASCIIInsert.ExportToCarrierFile(cf: TCarrierFile): Boolean;
   begin
     cf.LoadFromStream(Data);
     cf.SetFileType('TXT',0);
     ExportToCarrierFile:=True;
   end;

   function TASCIIInsert.EnoughSpaceToHide(n: Longint): Boolean;
   begin
     if n>GetAvailSize then EnoughSpaceToHide:=False else EnoughSpaceToHide:=True;
   end;

   function TASCIIInsert.Encode(ToHide: TDataFile): Boolean;
   var
     newData:     TMemoryStream;
     Buffer:      Array[0..1023] of Byte;
     BytesRead:   Integer;
     HideStream:  TMemoryStream;
     HideBuffer:  Array[0..1023] of Byte;
     Insert:      Array[0..7] of Byte;
     HideRead:    Integer;
     CPos:        Integer;
     i,j:         Integer;
     val:         Byte;
     lastwritten: Integer;
     last0d:      Boolean;
     Buffer2:     Array[0..1023] of Byte;
     p:           Integer;
     Cancel:      Boolean;
   begin
     if EnoughSpaceToHide(ToHide.GetSize) then begin
       Cancel:=False;
       HideStream:=TMemoryStream.Create;
       ToHide.SaveToStream(HideStream);
       newData:=TMemoryStream.Create;
       Data.Seek(0,soFromBeginning);
       BytesRead:=Data.Read(Buffer,1024);
       CPos:=0;
       lastwritten:=-1;
       HideRead:=1024;
       HideStream.Seek(0,soFromBeginning);
       last0d:=False;
       Percent:=0;
       p:=Trunc(HideStream.Size/1024);
       if Assigned(FPercentChange) then FPercentChange(self,Percent);
       Application.ProcessMessages;
       while (HideRead=1024) and not(Cancel) do begin
         HideRead:=HideStream.Read(HideBuffer,1024);
         for i:=0 to HideRead-1 do begin
           for j:=7 downto 0 do begin
             if (HideBuffer[i] and (1 shl j))<>0 then Insert[7-j]:=$09 else Insert[7-j]:=$20;
           end;
           while ((Buffer[CPos]<>$0d) and ((Buffer[CPos]<>$0a) or ((Buffer[CPos]=$0a) and (last0d)))) do begin
             last0d:=False;
             if CPos<BytesRead-1 then Inc(CPos)
             else begin
               for j:=0 to CPos-lastwritten-1 do Buffer2[j]:=Buffer[j+lastwritten+1];
               newData.Write(Buffer2,CPos-lastwritten);
               BytesRead:=Data.Read(Buffer,1024);
               CPos:=0;
               lastwritten:=-1;
             end;
           end;
           if (Buffer[CPos]=$0d) then last0d:=True;
           for j:=0 to CPos-lastwritten-2 do Buffer2[j]:=Buffer[j+lastwritten+1];
           newData.Write(Buffer2,CPos-lastwritten-1);
           newData.Write(Insert,8);
           lastwritten:=CPos-1;
           if CPos<BytesRead-1 then Inc(CPos)
           else begin
             for j:=0 to CPos-lastwritten-1 do Buffer2[j]:=Buffer[j+lastwritten+1];
             newData.Write(Buffer2,CPos-lastwritten);
             BytesRead:=Data.Read(Buffer,1024);
             CPos:=0;
             lastwritten:=-1;
           end;
         end;
         Percent:=Percent+p;
         if Assigned(FPercentChange) then FPercentChange(self,Percent);
         if Assigned(FWantCancel) then FWantCancel(self,Cancel);
         Application.ProcessMessages;
      end;
       for j:=lastwritten+1 to BytesRead-1 do Buffer2[j-lastwritten-1]:=Buffer[j];
       newData.Write(Buffer2,BytesRead-1-lastwritten);
       if Data.Size>Data.Position then newData.CopyFrom(Data,Data.Size-Data.Position);
       Data.Free;
       Data:=newData;
       Percent:=100;
       if Assigned(FPercentChange) then FPercentChange(self,Percent);
       Application.ProcessMessages;
     end
     else Encode:=False;
   end;

   function TASCIIInsert.Decode(ResultFile: TDataFile): Boolean;
   var
     S24:            Array[0..2] of Byte;
     Size:           Integer;
     outStrm:        TMemoryStream;
     DataBuffer:     Array[0..1023] of Byte;
     DataWritten:    Integer;
     CarrierBuffer:  Array[0..1023] of Byte;
     CarrierRead:    Integer;
     i,j:            Integer;
     d,c:            Integer;
     val:            Integer;
     linefeed:       Boolean;
     Cancel:         Boolean;
   begin
     // decode first 3 bytes
     Cancel:=False;
     Data.Seek(0,soFromBeginning);
     i:=0;
     d:=0;
     c:=0;
     CarrierRead:=Data.Read(CarrierBuffer,1024);
     linefeed:=False;
     Percent:=0;
     if Assigned(FPercentChange) then FPercentChange(self,Percent);
     Application.ProcessMessages;
     while i<3 do begin
       val:=0;
       while ((CarrierBuffer[c]<>$d) and ((CarrierBuffer[c]<>$0a) or ((CarrierBuffer[c]=$0a) and (linefeed)))) do begin
         linefeed:=False;
         if ((c>CarrierRead-2) and (CarrierRead=1024)) then begin
           CarrierRead:=Data.Read(CarrierBuffer,1024);
           c:=0;
         end
         else Inc(c);
       end;
       if CarrierBuffer[c]=$d then linefeed:=True;
       for j:=7 downto 0 do begin
         if CarrierBuffer[c-j-1]=$09 then val:=val+(1 shl j);
       end;
       if c<CarrierRead-1 then Inc(c)
       else begin
         CarrierRead:=Data.Read(CarrierBuffer,1024);
         c:=0;
       end;
       S24[d]:=val;
       Inc(DataWritten);
       Inc(d);
       Inc(i);
     end;
     // then decode other data
     Size:=S24[0]+(S24[1] Shl 8)+(S24[2] Shl 16);
     outStrm:=TMemoryStream.Create;
     DataWritten:=0;
     i:=0;
     d:=0;
     while (i<Size) and not(Cancel) do begin
       if (d=1024) then begin
         outStrm.Write(DataBuffer,1024);
         DataWritten:=0;
         d:=0;
       end;
       val:=0;
       val:=0;
       while ((CarrierBuffer[c]<>$d) and ((CarrierBuffer[c]<>$0a) or  ((CarrierBuffer[c]=$0a) and (linefeed)))) do begin
         linefeed:=False;
         if ((c=CarrierRead) and (CarrierRead=1024)) then begin
           CarrierRead:=Data.Read(CarrierBuffer,1024);
           c:=0;
           if CarrierRead=0 then begin
              Cancel:=True;
              break;
           end;
         end
         else Inc(c);
       end;
       if CarrierBuffer[c]=$d then linefeed:=True;
       for j:=7 downto 0 do begin
         if CarrierBuffer[c-j-1]=$09 then val:=val+(1 shl j);
       end;
       if c<CarrierRead-1 then Inc(c)
       else begin
         CarrierRead:=Data.Read(CarrierBuffer,1024);
         c:=0;
       end;
       DataBuffer[d]:=val;
       Inc(DataWritten);
       Inc(d);
       Inc(i);
       Percent:=Trunc(i/Size);
       if Assigned(FPercentChange) then FPercentChange(self,Percent);
       if Assigned(FWantCancel) then FWantCancel(self,Cancel);
       Application.ProcessMessages;
     end;
     outStrm.Write(DataBuffer,DataWritten);
     ResultFile.LoadFromStream(outStrm);
     outStrm.Free;
     Percent:=100;
     if Assigned(FPercentChange) then FPercentChange(self,Percent);
     Application.ProcessMessages;
     Decode:=True;
   end;

end.