Zip and Unzip, the MFC Way


Desktop-as-a-Service Designed for Any Cloud ? Nutanix Frame

This library allows creating, modifying and extracting zip archives in the compatible way with PKZIP and WinZip. Supported are all possible operations on the zip archive: creating, extracting, adding, deleting files from the archive, modifications of the existing archive. There is also the support for creating and extracting multiple disk archives (this is probably the first free code on the internet that supports disk spanned archives). This module uses compression and decompression functions from zlib library by Jean-loup Gailly and Mark Adler.

How to integrate with the project

Zip is a static library and statically links to compiled zlib.lib (version 1.13 nowadays). The zlib library can be replaced with a newer version providing you also replace the files: "zlib.h" and "zconf.h" in the Zip project. The Zip library uses MFC in a shared library as a Release and Debug Configuration. Your project must use MFC in the same way in the appropriate project configuration. You may need to adapt this to your needs. To add Zip library functionality to your project you need to link the library to the project. You can do this in at least two ways:

Method 1

Add "..\Zip\debug(release)\Zip.lib" to Project Settings->Link->Input->Object/library modules and add Zip directory to the preprocessor searches (Project Settings -> C++ -> Preprocessor -> Additional include directories).

Method 2 (simpler)

Insert Zip project into workspace and set project dependencies (your project dependent on Zip project).

How to use

The details about using this library are in the sources. The example available for download at the bottom of the page is an almost complete compression\decompression program. There are only main issues mentioned below about using this library. If you have a question about using the library and you can't find the answer here, don't hesitate to ask.

Compression and decompression

There are some functions defined for fast operations on archive; among others: AddNewFile(), ExtractFile(), DeleteFile(). You only need to call functions Open() - before and Close() - after using them.
Remember to call Close() function when you finish working with CZipArchive class.

Disk spanning

This library supports two kinds of disk spanning:
1. Disk spanning performed in the compatible way with all other main zip programs. It means that the archive can only be created on a removable device, the size of the volume is autodetected and the label is written to the disk. To use this kind of disk spanning you need to define a static callback function for changing disks and set it with SetSpanCallback() function.
2. Disk spanning performed in the internal mode, called in the sources TD span mode. This allows creating multi disk archives also on non-removable devices and with user-defined volume size. There is no need to set callback function in this mode.

This two disk spanning modes create volumes with compatible internal structure. It means that you can easily convert the volumes created in one mode to the other one by renaming the files (in TD mode each volume but last has a number as an extension).

There is a limited functions set available during work with multi disk archives. Only adding is allowed when creating an archive and only extracting when opening an existing one. Deleting files from these archives isn't allowed in any of these cases.

Class CZipArchive uses write buffer to make write operations extremly fast. You can change its size with SetAdvanced() function. While creating multi disk archive, set the size of the buffer to the maximum size of the volume  for the best performance.

Self extract support

The library automatically detects self-extracting archives. This is the simplest self-extract code :

int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
 CZipArchive zip;

 // get path of executable
 if (!::GetModuleFileName(hInstance, szBuff, _MAX_PATH))
  return -1;

 CString szDest;
 // ...
 // add the code here to get the destination directory 
 // from the user we assume it is in szDest variable

 zip.Open(szBuff, CZipArchive::openReadOnly); 
 // openReadOnly mode is necessary for self extract archives
 for (WORD i = 0; i < zip.GetNoEntries(); i++)
  zip.ExtractFile(i, szDest);

 return 0;

After compiling it and appending a zip archive to it (e.g. with the DOS command: copy /b SelfExtract.exe + ZipFile.zip FinalFile.exe) we have a self extracting archive.


The library throws the following exceptions: CMemoryException, CFileExeption and CZipException. The first two don't need an explanation. The last is thrown when some internal error occurs. Handling them may be done in the following way:

 // ...
 // some operations on Zip library
catch (CException* e)
 if (e->IsKindOf( RUNTIME_CLASS( CZipException )))
  CZipException* p = (CZipException*) e;
  //... and so on 
 else if (e->IsKindOf( RUNTIME_CLASS( CFileException )))
  CFileException* p = (CFileException*) e;
  //... and so on 
  // the only possibility is a memory exception I suppose
  //... and so on 


To run the example, integrate first Zip library into it (Zip library is not included in the example, you must download it separately); you should be asked at the beginnig about the location of the Zip project, if not, use one of the integration methods descripted above. If you don't put Zip library project at the same directory level what example is, you also have to change the path pointing to ZipArchive.h in the file testzipdlgdlg.h.

Last Words

This library does not support password encryption nor decryption due to lack of documentation I have. If anyone is so kind to send me the algorithm, I will add this feature next time.

Version History

  • 08.2000
    • Bugs fixed
  • 06.2000
    • the code has been completely rewritten since the very beginning;
    • the main improvements are:
    • disk spannig archive operations allowed
    • creation of the disk spanning archives with the user-defined volume size
    • ability to modify existing archives (add, delete files)
    • modification self-extracting archives
    • write buffer used for faster disk write operations
    • one class for zip and unzip functions
    • fast adding, deleting and extracting files with a single funct call
  • 03.2000
    • international characters in filenames inside archive are now converted in a compatible way with other archivers (they are stored converted to OEM inside archive).
  • 01.2000

  • first version; it is just modified code from zip.c and unzip.c files written by Gilles Vollant and distributed with zlib library; the modifications are as follows
    • added class' wrappers
    • several bugs fixed
    • several enhancements added
    • MFC support added
    • memory leaks eliminated when write error occurred
    • automatically free used memory on destruction or exception
    • modern error notification using exceptions


Download source - 92 Kb
Download demo project - 31 Kb

This article was originally published on November 7th, 2000

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