Zip-Ada

A rare case where Zip-Ada's LZMA encoder is much better than LZMA SDK's. Rare but still interesting, and with standard LZMA parameters (no specific tuning for that file): The compressed size with current revision (rev.#882) of Zip-Ada is slightly ... [More] worse (42,559 bytes). The file is part of the classic Canterbury Corpus compression benchmark data set. [Less]

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 ... [More] output streaming into Zip archives. Zip.Compress: Preselection method detects Audacity files (.aup, .au) and compresses them better. [Less]

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 ... [More] 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. [Less]

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 ... [More] 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). Zip-Ada Web site: http://unzip-ada.sf.net [Less]

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 ... [More] 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. [Less]

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 ... [More] Preselection), Preselection_2. Preselection methods use now entry name extension and size for improving compression, while remaining 1-pass methods. [Less]