unit CombineFilesUnit;

interface

uses
  Windows, Messages, SysUtils, Classes;

type
TFileInfoData = record
  Size:Cardinal;
  Offset:Cardinal;
  Name:array[0..30] of Char;
end;

TCombineFilesHeader = record
  NumberOfFiles:integer;
  FileInfo:array[0..19] of TFileInfoData;
end;

TMemoryStreamArray = array[0..19] of TMemoryStream;

function CombineFiles(MS:TMemoryStream;FileList:TStrings):Boolean;
function GetFileHeader(CombFile:string;var CFH:TCombineFilesHeader):Boolean;
procedure SplitCombFile(CombFile:string;
                   var MSA:TMemoryStreamArray;var CFH:TCombineFilesHeader);
function FindFileIndex(CombFile, FileName:string):integer;
function ExtractFileFromCombined(CombFile:string;
                             indx:integer; MS:TMemoryStream):Boolean;
function AddCombineFile(SourceFile,AddFile:string):Boolean;
function DeleteFromCombFile(CombFile:string; DeleteIndex:integer):Boolean;


implementation


function CombineFiles(MS:TMemoryStream;FileList:TStrings):Boolean;
var
  CFH:TCombineFilesHeader;
  EachFile:TMemoryStream;
  i,Num:integer;
begin
  result := false;
  if FileList.Count = 0 then exit;
  if FileList.Count > 20 then Num := 20 else Num := FileList.Count;

  FillChar(CFH,SizeOf(TCombineFilesHeader),#0);
  MS.Clear;

  EachFile := TMemoryStream.Create;
  try
    CFH.NumberOfFiles := Num;
    MS.Position := SizeOf(CFH);
    for i := 0 to Num-1 do begin
      EachFile.LoadFromFile(FileList[i]);
      with CFH.FileInfo[i] do begin
        Size := EachFile.Size;
        Offset := MS.Position;
        StrPLCopy(Name,ExtractFileName(FileList[i]),30);
      end;
      MS.Write(EachFile.Memory^,EachFile.Size);
    end;
    MS.Position := 0;
    MS.Write(CFH,SizeOf(CFH));
    result := true;
  finally
    EachFile.Free;
  end;
end;

function GetFileHeader(CombFile:string;var CFH:TCombineFilesHeader):Boolean;
var
  FS:TFileStream;
begin
  FS := TFileStream.Create(CombFile,fmOpenRead or fmShareDenyWrite);
  try
    result := false;
    FS.Position := 0;
    FS.Read(CFH,SizeOf(CFH));
    result := true;
  finally
    FS.Free;
  end;
end;

procedure SplitCombFile(CombFile:string;
             var MSA:TMemoryStreamArray;var CFH:TCombineFilesHeader);
var
  MS:TMemoryStream;
  i:integer;
begin
  if not GetFileHeader(CombFile,CFH) then exit;

  MS := TMemoryStream.Create;
  
  for i := 0 to CFH.NumberOfFiles-1 do
    MSA[i] := TMemoryStream.Create;

  try
    MS.LoadFromFile(CombFile);
    for i := 0 to CFH.NumberOfFiles-1 do begin
      MSA[i].SetSize(CFH.FileInfo[i].Size);
      MS.Position := CFH.FileInfo[i].Offset;
      MS.Read(MSA[i].Memory^,CFH.FileInfo[i].Size);
    end;
  finally
    MS.Free;
  end;
end;

function FindFileIndex(CombFile, FileName:string):integer;
var
  CFH:TCombineFilesHeader;
  i:integer;
begin
  result := -1;
  if GetFileHeader(CombFile,CFH) then
    for i := 0 to CFH.NumberOfFiles-1 do
      if UpperCase(CFH.FileInfo[i].Name) = UpperCase(FileName) then  begin
        result := i;
        exit;
      end;
end;

function ExtractFileFromCombined(CombFile:string;
                             indx:integer; MS:TMemoryStream):Boolean;
var
  CFH:TCombineFilesHeader;
  Source:TMemoryStream;
begin
  result := false;
  if not GetFileHeader(CombFile,CFH) then exit;
  if (indx < 0) or (indx > CFH.NumberOfFiles-1) then exit;
  Source := TMemoryStream.Create;
  try
    Source.LoadFromFile(CombFile);
    MS.Clear;
    Source.Position := CFH.FileInfo[indx].Offset;
    MS.SetSize(CFH.FileInfo[indx].Size);
    Source.Read(MS.Memory^,CFH.FileInfo[indx].Size);
    result := true;
  finally
    Source.Free;
  end;
end;

function AddCombineFile(SourceFile,AddFile:string):Boolean;
var
  CFH:TCombineFilesHeader;
  MS,EachFile:TMemoryStream;
  Num:integer;
begin
  MS := TMemoryStream.Create;
  EachFile := TMemoryStream.Create;
  try
    MS.LoadFromFile(SourceFile);
    MS.Position := 0;
    MS.Read(CFH,SizeOf(CFH));
    Num := CFH.NumberOfFiles;
    if Num < 20 then begin
      EachFile.LoadFromFile(AddFile);
      CFH.NumberOfFiles := Num+1;
      MS.Position := MS.Size;
      with CFH.FileInfo[Num] do begin
        Size := EachFile.Size;
        Offset := MS.Position;
        StrPLCopy(Name,ExtractFileName(AddFile),30);
      end;
      MS.Write(EachFile.Memory^,EachFile.Size);
      MS.Position := 0;
      MS.Write(CFH,SizeOf(CFH));
      MS.SaveToFile(SourceFile);
      result := true;
    end else
      result := false;
  finally
    MS.Free;
    EachFile.Free;
  end;
end;

function DeleteFromCombFile(CombFile:string; DeleteIndex:integer):Boolean;
var
  CFH,NEWCFH:TCombineFilesHeader;
  Source,NewComb,Each:TMemoryStream;
  i,indx:integer;
begin
  result := false;
  if GetFileHeader(CombFile,CFH) then begin
    if (DeleteIndex > CFH.NumberOfFiles-1) or (DeleteIndex < 0) then Exit;
  end else
    Exit;

  FillChar(NEWCFH,SizeOf(TCombineFilesHeader),#0);
  Source := TMemoryStream.Create;
  NewComb := TMemoryStream.Create;
  Each := TMemoryStream.Create;
  try
    Source.LoadFromFile(CombFile);
    indx := 0;
    NEWCFH.NumberOfFiles := CFH.NumberOfFiles-1;
    NewComb.Position := SizeOf(NEWCFH);
    for i := 0 to CFH.NumberOfFiles-1 do begin
      if i = DeleteIndex then continue;
      NEWCFH.FileInfo[indx] := CFH.FileInfo[i];
      NEWCFH.FileInfo[indx].Offset := NewComb.Position;
      Source.Position := CFH.FileInfo[i].Offset;
      Each.SetSize(CFH.FileInfo[i].Size);
      Source.Read(Each.Memory^,CFH.FileInfo[i].Size);
      NewComb.Write(Each.Memory^,CFH.FileInfo[i].Size);
      Each.Clear;
      Inc(indx)
    end;
    NewComb.Position := 0;
    NewComb.Write(NEWCFH,SizeOf(CFH));
    NewComb.SaveToFile(CombFile);
    result := true;
  finally
    Source.Free;
    NewComb.Free;
    Each.Free;
  end;
end;

end.