Create sample ZIP files

Result#

Via git archive, zero compression:

• dir1.via-git-c0.zip
• dir64-bigfile.via-git-c0.zip
• dir64-bigtotal.via-git-c0.zip
• dir64-many.via-git-c0.zip
• dir64-all.via-git-c0.zip

Sample dir (dir1/)#

dir1/
    README.md
    src/
        foo.py

mkdir dir1
cd dir1
echo 'Welcome!' > README.md
mkdir src
echo "print(2 + 3)" > src/foo.py
git init
git add .
git commit -m -

Creating .zip files via git archive#

cd dir1
git archive --format=zip -0 HEAD > ../dir1.via-git-c0.zip

Some details about the .zip file that this creates:

• PK34/PK12 pairs are created for items named README.md, src/, and src/foo.py
• Both the PK34s and the PK12s include the UT extra field to provide one-second-resolution UTC timestamps
• These item timestamps match the commit's timestamp, not the timestamp at which git archive was run
• The last 40 bytes of the file are the ASCII hex characters of the commit ID (via the "comment" field of the PK56 record)
• zip64 records are not used in this file

Zip64 records would be used if the files in the archive were large enough and/or numerous enough to require zip64. See Zip64 examples.

Creating .zip files via zip#

This is the Info-ZIP implementation, bundled with most platforms as zip.

TODO

Creating .zip files via ditto#

This is macOS's implememtation for the File → Compress action.

TODO

TODO: example with resource forks and various metadata

Creating .usdz files via usdzip#

TODO

Details:

• USDZ files require 64-byte alignment for the offset of the start of each file's content. This is implemented via padding in the PK34's "extra" field when needed.

Zip64 examples#

dir64-bigfile/
    README.md
    files/
        bigfile         5GB

dir64-bigtotal/
    README.md
    files/
        mediumfile1     3GB
        mediumfile2     3GB

dir64-many/
    README.md
    files/
        text00000.txt   "file 00000\n"
        ...
        text70000.txt   "file 70000\n"

dir64-all/
    ...the union of all of the above filesets...

...TODO: creating these...

cd dir64-bigfile && git archive --format=zip -0 HEAD > ../dir64-bigfile.via-git-c0.zip
cd ../dir64-bigtotal && git archive --format=zip -0 HEAD > ../dir64-bigtotal.via-git-c0.zip
cd ../dir64-many && git archive --format=zip -0 HEAD > ../dir64-many.via-git-c0.zip
cd ../dir64-all && git archive --format=zip -0 HEAD > ../dir64-all.via-git-c0.zip