Zip-Ada / News: Recent posts

New features:

• UnZip.Streams: added Set_Index & Index subprograms for inward streams from Zip archives.
• Zip.Create: added procedure Add_Empty_Folder

New feature in version 58 (as frozen in rev. 922): Support for Zip_64 archives. The Zip_64 format extension is needed when there are more than more than 65535 entries or more than 4 GiB data for a single entry's compressed or uncompressed size, or for a whole archive.

A rare case where Zip-Ada's LZMA encoder is much better than LZMA SDK's. Rare but still interesting, and with, on Zip-Ada's side, standard LZMA parameters (no specific tuning for that file):

The compressed size with current public revision (rev.#882) of Zip-Ada is slightly worse (42,559 bytes).... read more

Changes in '57', 02-Oct-2020 [rev. 799]:

• UnZip: fixed bad decoding case for the Shrink (LZW) format,
  on some data compressed only by PKZIP up to v.1.10,
  release date 1990-03-15.
• Zip.Create: added Zip_Entry_Stream_Type for doing output
  streaming into Zip archives.
• Zip.Compress: Preselection method detects Audacity files (.aup, .au)
  and compresses them better.

Changes in '56', 17-Jan-2020 [rev. 780]:

• Zip: the Zip_info type is now controlled (no need to call Delete;
  additionally, clones are done correctly).
• UnZip.Streams: added Size and Name functions for Zipped_File_Type.
• LZ77: added nice simple LZ77 compressor by Rich Geldreich, Jr.
• (Tools) Added Zip_Dir_List.
• Some refactoring was needed for -gnatwh warning switch (warnings for
  hiding declarations). Subprogram Create in package Zip.Create
  was renamed to Create_Archive.
• Adapted to -gnatytc style checks.
• Better names for some exceptions (the old names
  can be still used); better exception messages.

Latest commit (rev. 796) adds a stronger and faster compression specifically for Audacity files (.aud, .au) for hot backups of audio editing projects.
More about it in this article.

Presentation is available as PDF and PPT.

Zip-Ada v.55

Changes in '55', 22-Nov-2018:

• Zip_Streams: ZS_Size_Type is now 64-bit signed, enabling Zip.Create
  to capture archive size overflows in Zip_32 mode.
• Zip.Create raises Zip_Capacity_Exceeded when archive creation exceeds
  the Zip_32 format's capacity: 4GB total size, 65,535 entries.
• Zip.Create is now using an Ada 2005+'s Containers's Hashed Maps;
  creation is much faster on Zip archives with many entries.
• (Tools) ReZip has a new option for working only with its own internal
  compression algorithms - those provided by Zip.Compress.
  This option is useful if external tools are not available.
• New Trained_Compression package: generic streaming encoder-decoder
  engine with the capability of training the engine with data known
  in advance, in order to achieve better compression. Not Zip-related.
• Minimum required Ada version is now Ada 2005 (was Ada 95 before).... read more

Changes:

• Zip.Compress.Deflate: use of L1_tweaked measure; adjusted
  threshold for activating new compression block
• Source gardening: removal of needless "use" clauses, these cases
  are detected by GNAT Community 2018

• Decompression and loading of archive directory are more
  resistant to fuzzing attacks. From that version, a random data
  passed as a Zip archive will be either valid (with an extremely tiny
  probability), or, for loading the archive directory, issue
  Zip.Archive_Corrupted. Data extraction will issue one of:
  Zip.Archive_Corrupted, UnZip.CRC_Error, UnZip.Wrong_password,
  UnZip.Unsupported_method, UnZip.Not_supported.
• Zip.Compress & ReZip: fix in local header generation: EOS flag for
  LZMA format is properly set in any situation LZMA is actually used.
• (Tools) ZipAda tool has a more useful recursive
  directory search (-r2 option).
• (Tests) Added Fuzzip, a fuzzing tool for the compression side.

Fix: Zip.Create.Add_Stream: LZMA_EOS_Flag_Bit was missing in header on Preselection methods, when a LZMA compression was selected.
This header glitch was detected by 7-Zip v.17.01 (but not 16.x) on archives created by Zip-Ada using Preselection methods.

Changes in '52', 08-Oct-2016:
- UnZip.Streams: all procedures have an additional (optional)
Ignore_Directory parameter.
- Zip.Compress has the following new methods with improved compression:
LZMA_3, Preselection_1 (replaces Preselection), Preselection_2.
Preselection methods use now entry name extension and size for
improving compression, while remaining 1-pass methods.

Changes in '51', 27-Aug-2016:
- LZMA.Encoding has been added; it is a standalone compressor,
see lzma_enc.adb for an example of use.
- Zip.Compress provides now LZMA_1, LZMA_2 methods. In other words, you
can use the LZMA compression with Zip.Create.
- Zip.Compress has also a "Preselection" method that selects
a compression method depending on hints like the uncompressed size.
- Zip.Compress.Deflate: Deflate_1 .. Deflate_3 compression is
slightly better.

• LZMA.Encoding: started July 28th, first working version August 16th (revision 457).
• Zip-Ada's Zip.Compress makes use of LZMA encoding since revision 459.

More details here.

... can be read here: http://gautiersblog.blogspot.ch/2016/04/zip-ada-v50.html

Available from now here: http://sourceforge.net/projects/unzip-ada/files/zipada50-bin-win32.zip/download
To access it from the project page, click on "Browse All Files".

In a nutshell, there are now, finally, fast and efficient compression methods available.

• Changes in '50', 31-Mar-2016:
• Zip.Compress.Shrink is slightly faster
• Zip.Compress.Deflate has new compression features:
  • Deflate_Fixed is much faster, with slightly better compression
  • Deflate_1 was added: strength similar to zlib, level 6
  • Deflate_2 was added: strength similar to zlib, level 9
  • Deflate_3 was added: strength similar to 7-Zip, method=deflate, level 5

• Zip.Compress.Deflate: first variant with 'dynamic' compression working

Encryption implemented (portable Zip 2.0 encryption scheme)

Under test: encryption (the Zip 2.0 flavor).
Feedback is welcome!

LZMA method has been added for decompression

• Changes in '38', 27-Feb-2010:
• ReZip: added '-fast_dec' and '-rand_stable' options
• Zip.Create: fixed major bottlenecks around Dir_entries
  -> 5x faster overall for 1000 files, 356x for 100'000 files !

• Changes in '37', 1-Jan-2010:

• Minor changes which leads to a significant speedup on GNAT;
  active use of Ada.Calendar can be totally avoided if this is desired

• Changes in '36', 21-Nov-2009:

• BZip2 method added for decompression
• Added Zip.Traverse_verbose

• Added an UnZip.Extract to extract all files, using a Zip_Info variable

• Changes in '35', 2-Nov-2009:

• major performance improvement:
  decompression 10x faster, compression 3x faster (figures for GNAT),
  thanks to a workaround for slow 'Read, 'Write attributes
  in GNAT & ObjectAda
• ReZip: HTML display improved

• Changes in '36', 21-Nov-2009:
• BZip2 method added for decompression
• Added Zip.Traverse_verbose

• Added an UnZip.Extract to extract all files, using a Zip_Info variable

• Changes in '35', 2-Nov-2009:

• major performance improvement:
  decompression 10x faster, compression 3x faster (figures for GNAT),
  thanks to a workaround for slow 'Read, 'Write attributes
  in GNAT & ObjectAda
• ReZip: HTML display improved... read more

• Changes in '33', 18-Jun-2009:
• UnZip: added extract_as_text option (cf. UnZipAda with -a option)
• Zip: Zip_comment function added (cf. UnZipAda with -z option)

Zip-Ada is now used in the Scala musical freeware ( http://www.huygens-fokker.org/scala/ )