readme.txt

给出了 zip 压缩算法的完整实现过程。

Macintosh Port of Info-ZIP's Zip
and UnZip
By Dirk Haase, [e-mail]
Home page: www.sitec.net/maczip
Mirror page:
www.haase-online.de/dirk/maczip
================================



Abstract:
---------
MacZip is a cross-platform compatible tool that
includes both Zip (for compression) and UnZip (for extraction).

Zip is a compression and file packaging utility for Unix,
VMS, MSDOS, OS/2, Windows 9x, Windows NT, Atari, Macintosh,
Amiga, Acorn RISC OS, and other systems.

UnZip unpacks zip archives.
The Zip and UnZip programs can process archives pro-
duced by PKZIP, and PKZIP and PKUNZIP can work with
archives produced by zip. Zip version 2.2 is compatible
with PKZIP 2.04.



Requirements
------------
MacZip requires at least System 7 and a Macintosh with a minimum of a
Motorola 68020 or PowerPC 601 processor. Other configurations may work
but it is not tested at all.

The application is distributed as a fat binary with both regular 68K
and native PowerPC versions included.



Installation
------------
Move the executable(s) somewhere--for example, drag it (or them) to your
Applications folder.  For easy access, make an alias in the Launcher Control
Panel or directly on your desktop.
The GUI is very simple. It was not my intention to make a full-blown GUI,
however I think it is comfortable enough to use it as regular tool.

This port supports also Apple-event. So you can install it in your
WWW-Browser as a helper app.

For more Info about the contents of this package, take a look into
the "macos/Contents" (or :macos:Contents) file. Some notes on how to
rebuild the Macintosh applications can be found in INSTALL.



Usage:
------

Basically there are four ways to start MacZip:

a) Drag'n Drop
   To extract an archive, drop an archive on MacZip.
   To compress files drop a file, folder or volume on MacZip.
   Note: You cannot drop more than one item at the same time.



b) using the Dialog box (Menu: File -> Zip/Unzip):
   * Compression (Zip):
   - Go to "File -> Zip"and the "Zip Options" Dialog Box appears.
   - Click on "Location of the compressed File"
   - The "Select an archive" dialog box appears
        a) select a existing zip archive
           -> Your files will be added to that zip archive.
        b) select a folder and name your new zip archive
           -> a new zip archive will be created with your files.
   - Select one or more check boxes if you want.
     see Zip.txt for more information.
   - Click on "File or Folder to Compress"
   - The "Select a File or Folder" dialog box appears
        a) select a file
           -> This file will be compressed.
        b) select a folder
           -> the contents of the folder will be compressed.
   - Click on "Start Zip" to start the task.

  * Extraction (Unzip):
   - Go to "File -> Unzip"and the "Unzip Options" Dialog Box appears.
   - Click on "Location of the compressed File"
   - The "Select an archive" dialog box appears
   - select a existing zip archive
   - Select one or more check boxes if you want.
     see Unzip.txt for more information.
   - Click on "Location of the extracted Files"
   - The "Select a Folder" dialog box appears
        a) select a file
           -> This file will be compressed.
        b) select a folder
           -> the contents of the archive will be extracted
              into this folder.
   - Click on "Start Unzip" to start the task.



c) Using the Command line (Menu: File->Command Line):
   The Zip & UnZip tools are command line tools. So the behavior is exactly
   the same like the Zip & UnZip tools on Unix or Windows/DOS. This means,
   if you want to zip some files, you have to write a command line like this:
   "zip [switches] path_to_zip_archive path_to_files_folders"

   - Go to "File" and select "Command Line" and the "MacZip Entry box"
     Dialog Box appears.

   An example:

   a: your zip may be created at
           Macintosh HD:applications:archive.zip

   b: your files may be found at
           Macintosh HD:somewhere:my_folder_to_archive:*

   Note: At the end of the path there must be a filename or a wild card !
   (see Footnote: 1 wild card, 2 Mac path names)

   So the command line should look like (one line!):

   zip "Macintosh HD:applications:archive.zip" "Macintosh HD:somewhere:my_folder_to_archive:*"

   - Click on "Enter" to start the task.

   Since you can not set a default folder you have to enter always a
   full qualified path names. Full-qualified path names are path names
   including the Volume name ! (see Footnote: 2 Mac path names)



d) Using Applescript:

There is only one additional event defined: "do_cmd". You can enter
every valid command line. The first word must be "zip" or "unzip" to
select the action (compress or extraction).

See sample Applescript:

        tell application "MacZip (PPC)"
            activate
            with timeout of 90000 seconds
                do_cmd "zip -rjjN Volume:archive \"My Volume:*\" "
            end timeout
        end tell

This script opens MacZip, brings it to the foreground on the Mac, starts the
zip action with the command line: zip -rjjN Volume:archive "My Volume:*" .




A short introduction is also available online:
http://www.sitec.net/maczip/How-To-Do/

It's possible to stop the run of Zip/Unzip with the well
known shortcut [Command] + [.].


---------------------------------------------------------------------------

There are some Mac-specific switches available.
Zip Module:
       -df    [MacOS] Include only data-fork of files zipped into
              the  archive.   Good for exporting files to foreign
              operating-systems.  Resource-forks will be  ignored
              at all.

       -jj    [MacOS] record Fullpath (+ Volname).  The  complete
              path  including  volume  will be stored. By default
              the relative path will be stored.

       -S     [MSDOS, OS/2, WIN32 and ATARI] Include  system  and
              hidden files.
              [MacOS]  Includes finder invisible files, which are
              ignored otherwise.

Unzip Module:
       -E     [MacOS only] display contents of MacOS extra  field
              during restore operation.

       -i     [MacOS only] ignore filenames stored in MacOS extra
              fields.  Instead,  the  most  compatible   filename
              stored in the generic part of the entry's header is
              used.

       -J     [MacOS only] ignore MacOS extra fields.  All Macin-
              tosh  specific  info  is  skipped.  Data-fork   and
              resource-fork are restored as separate files.


Select [File]->[Get Help on Zip/Unzip] for a complete list
of switches.



Limitations / Problems:
-----------------------

    - Aliases are not supported. I tried, but I got broken aliases
      This port will silently ignore all aliases.
      It's on my to-do list for future releases.

    - Zip needs much memory to compress many files:
      You may need to increase the 'Preferred Size' in 'Get Info'.
      Values of 12 Megabytes or more are possible

    - Unzip needs about 500 Kbytes of memory to unzip no matter
      how many files were compressed and expanded.

    - and finally one big macintosh-related problem:
      This port has one weak point: It's based on path names.
      As you may be already know: Path names are not unique on a Mac !
      The main reason is that an attempt to implement support exact saving of
      the MacOS specific internal file structures would require a throughout
      rewrite of major parts of shared code, probably sacrifying compatibility
      with other systems.
      I have no solution at the moment. The port will just warn you if you try
      zip from / to a volume which has a duplicate name.
      MacZip has problems to find the archive or the files.
      My (Big) recommendation: Name all your volumes with a unique name and
      MacZip will run without any problem.


Known Bugs:

    - crypted files in a zip archive are sometimes corrupt:
      I get an error message: invalid compressed data to inflate.
      Appearance of this error is purely be chance:
      I did a small test: Unzipping an archive containing 3589 files
      56 files fails to unzip, so about 1.5%.
      Root cause is completely unclear to me :(

I strongly recommend to test your archive (e.g. unzip -t archive).





Zip Programs / Macintosh Extra-Data:
-----------------------------------------
A brief overview:
Currently, as far as I know, there are 4 Zip programs available
for the Macintosh platform.
These programs build (of course) different variants of Zip files:

    - Info-ZIP's first Port of Zip. Ported by Johnny Lee
      This Port is rather outdated and no longer supported (since 1992).
      68K only. Only minimal Mac-info is stored (Creator/Type,
      Finder attributes). Creator/Type: '????' / '????'
      Until year 1998, only UnZip 5.32 survived.

    - ZipIt by Tom Brown. This is Shareware and still supported I think.
      ZipIt has a nice GUI, but I found it can't handle large Zip files
      quite well. ZipIt compresses Macintosh files using the Mac Binary
      format. So, transferring files to other platforms is not so easy.
      Only minimal Mac-info is stored (Creator/Type, Finder attributes).
      Mac filenames are changed to a most compatible filename.
      Creator/Type: 'ZIP ' / 'ZIP '

    - PKZIP/mac v2.03/210d. This is Shareware.
      This Zip implementation for the Mac can be found on ASI's web site
      (http://www.asizip.com/products/products.htm).  The name of this
      program is misleading, it is NOT a product from PKWARE.  ASI's last
      release version is v2.03, and they also offer a newer beta version
      PKZIP/mac 210d. But even the Beta version is rather outdated (1995).
      Only minimal Mac-info is stored (Creator/Type, Finder attributes).
      The Zipfile format looks like incompatible to other platforms.
      (More details about the compatibility issue can be found in
      proginfo/3rdparty.bug!). Type: 'PKz1'
      Mac filenames are restored without any change.

and finally:
    - Info-ZIP's latest Port of Zip. MacZip 1.0. Ported by me :-)
      It is supported (of course) and up to date. Full set of macintosh
      info is stored: Creator/Type, Finder attributes, Finder comments,