Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

Delphi XE2 TZipFile: replace a file in zip archive

I'd like to replace a file (= delete old and add new) in a zip archive with the Delphi XE2/XE3 standard System.Zip unit. But there are no replace/delete methods. Does anybody have an idea how it could be achieved without needing to extract all files and add them to a new archive?

I have this code, but it adds the "document.txt" once more if it's already present:

var
  ZipFile: TZipFile;
  SS: TStringStream;
const
  ZipDocument = 'E:\document.zip';
begin
  ZipFile := TZipFile.Create; //Zipfile: TZipFile
  SS := TStringStream.Create('hello');
  try
    if FileExists(ZipDocument) then
      ZipFile.Open(ZipDocument, zmReadWrite)
    else
      ZipFile.Open(ZipDocument, zmWrite);

    ZipFile.Add(SS, 'document.txt');

    ZipFile.Close;
  finally
    SS.Free;
    ZipFile.Free;
  end;
end;

Note: I used TPAbbrevia before (that did the job), but I'd like to use Delphi's Zip unit now. So please do not answer something like "use another library". Thank you.

like image 692
oxo Avatar asked Oct 31 '12 18:10

oxo


1 Answers

I'd recommend Abbrevia because I'm biased :), you already know it, and it doesn't require any hacks. Barring that, here's your hack:

type
  TZipFileHelper = class helper for TZipFile
    procedure Delete(FileName: string);
  end;

{ TZipFileHelper }

procedure TZipFileHelper.Delete(FileName: string);
var
  i, j: Integer;
  StartOffset, EndOffset, Size: UInt32;
  Header: TZipHeader;
  Buf: TBytes;
begin
  i := IndexOf(FileName);
  if i <> -1 then begin
    // Find extents for existing file in the file stream
    StartOffset := Self.FFiles[i].LocalHeaderOffset;
    EndOffset := Self.FEndFileData;
    for j := 0 to Self.FFiles.Count - 1 do begin
      if (Self.FFiles[j].LocalHeaderOffset > StartOffset) and
         (Self.FFiles[j].LocalHeaderOffset <= EndOffset) then
        EndOffset := Self.FFiles[j].LocalHeaderOffset;
    end;
    Size := EndOffset - StartOffset;
    // Update central directory header data
    Self.FFiles.Delete(i);
    for j := 0 to Self.FFiles.Count - 1 do begin
      Header := Self.FFiles[j];
      if Header.LocalHeaderOffset > StartOffset then begin
        Header.LocalHeaderOffset := Header.LocalHeaderOffset - Size;
        Self.FFiles[j] := Header;
      end;
    end;
    // Remove existing file stream
    SetLength(Buf, Self.FEndFileData - EndOffset);
    Self.FStream.Position := EndOffset;
    if Length(Buf) > 0 then
      Self.FStream.Read(Buf[0], Length(Buf));
    Self.FStream.Size := StartOffset;
    if Length(Buf) > 0 then
      Self.FStream.Write(Buf[0], Length(Buf));
    Self.FEndFileData := Self.FStream.Position;
  end;
end;

Usage:

ZipFile.Delete('document.txt');
ZipFile.Add(SS, 'document.txt');
like image 127
Zoë Peterson Avatar answered Nov 16 '22 03:11

Zoë Peterson