unit ASCIIReplace;

interface

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

   type
     TASCIIReplace = 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 TASCIIReplace.Create;
   begin
     inherited Create;
   end;

   destructor TASCIIReplace.Destroy;
   begin
     inherited Create;
   end;

   function TASCIIReplace.GetAvailSize: Longint;
   var
     Buffer:      Array[0..1023] of Byte;
     BytesRead:   Integer;
     Hex20:       Integer;
     i:           Integer;
     p:           Integer;
     Cancel:      Boolean;
   begin
     inherited GetAvailSize;
     Cancel:=False;
     Hex20:=0;
     BytesRead:=1024;
     Data.Seek(0,soFromBeginning);
     p:=Trunc(Data.Size/1024);
     Percent:=0;
     if Assigned(FPercentChange) then FPercentChange(self,Percent);
     while (BytesRead=1024) and not(Cancel) do begin
       BytesRead:=Data.Read(Buffer,1024);
       for i:=0 to BytesRead-1 do begin
         if ((Buffer[i]=$20) or (Buffer[i]=$0)) then Inc(Hex20);
       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:=Hex20 div 8;
   end;

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

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

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

   function TASCIIReplace.Encode(ToHide: TDataFile): Boolean;
   var
     newData:     TMemoryStream;
     Buffer:      Array[0..1023] of Byte;
     BytesRead:   Integer;
     HideStream:   TMemoryStream;
     HideBuffer:  Array[0..1023] of Byte;
     HideRead:    Integer;
     CPos:        Integer;
     i,j:         Integer;
     val:         Byte;
     p:           Integer;
     Cancel:      Boolean;
   begin
     Cancel:=False;
     if EnoughSpaceToHide(ToHide.GetSize) then begin
       HideStream:=TMemoryStream.Create;
       ToHide.SaveToStream(HideStream);
       newData:=TMemoryStream.Create;
       Data.Seek(0,soFromBeginning);
       BytesRead:=Data.Read(Buffer,1024);
       CPos:=0;
       HideRead:=1024;
       HideStream.Seek(0,soFromBeginning);
       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 val:=$0 else val:=$20;
             while ((Buffer[CPos]<>$0) and (Buffer[CPos]<>$20)) do begin
               if CPos<BytesRead-1 then Inc(CPos)
               else begin
                 newData.Write(Buffer,BytesRead);
                 BytesRead:=Data.Read(Buffer,1024);
                 CPos:=0;
               end;
             end;
             Buffer[CPos]:=val;
             if CPos<BytesRead-1 then Inc(CPos)
             else begin
               newData.Write(Buffer,BytesRead);
               BytesRead:=Data.Read(Buffer,1024);
               CPos:=0;
             end;
           end;
         end;
         Percent:=Percent+p;
         if Assigned(FPercentChange) then FPercentChange(self,Percent);
         if Assigned(FWantCancel) then FWantCancel(self,Cancel);
         Application.ProcessMessages;
       end;
       newData.Write(Buffer,BytesRead);
       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 TASCIIReplace.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;
     Cancel:         Boolean;
   begin
     Cancel:=False;
     Percent:=0;
     if Assigned(FPercentChange) then FPercentChange(self,Percent);
     Application.ProcessMessages;
     // decode first 3 bits
     Data.Seek(0,soFromBeginning);
     i:=0;
     d:=0;
     c:=0;
     CarrierRead:=Data.Read(CarrierBuffer,1024);
     while i<3 do begin
       val:=0;
       for j:=7 downto 0 do begin
         while ((CarrierBuffer[c]<>$0) and (CarrierBuffer[c]<>$20)) do begin
           if ((c=CarrierRead) and (CarrierRead=1024)) then begin
             CarrierRead:=Data.Read(CarrierBuffer,1024);
             c:=0;
           end
           else Inc(c);
         end;
         if CarrierBuffer[c]=$20 then val:=val+(1 shl j);
         if c<CarrierRead-1 then Inc(c)
         else begin
           CarrierRead:=Data.Read(CarrierBuffer,1024);
           c:=0;
         end;
       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;
       for j:=7 downto 0 do begin
         while ((CarrierBuffer[c]<>$0) and (CarrierBuffer[c]<>$20)) do begin
           if ((c>CarrierRead-2) and (CarrierRead=1024)) then begin
             CarrierRead:=Data.Read(CarrierBuffer,1024);
             c:=0;
           end
           else Inc(c);
         end;
         if CarrierBuffer[c]=$20 then val:=val+(1 shl j);
         if c<CarrierRead-1 then Inc(c)
         else begin
           CarrierRead:=Data.Read(CarrierBuffer,1024);
           c:=0;
         end;
       end;
       if CarrierRead=0 then break;
       Percent:=Trunc(i/Size);
       if Assigned(FPercentChange) then FPercentChange(self,Percent);
       if Assigned(FWantCancel) then FWantCancel(self,Cancel);
       Application.ProcessMessages;
       DataBuffer[d]:=val;
       Inc(DataWritten);
       Inc(d);
       Inc(i);
     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.