SWCompression

• Minimum required version of BitByteData is now 1.4.0.
• Updated to support Swift 4.2.
• Added default values to the properties of LZMAProperties struct based on the documentation from LZMA SDK.
• Added init() to LZMAProperties struct which sets lc, lp, pb, and dictionarySize properties to their default values.
• Improved the detection of Swift versions less than 4.2 in the workaround for the crash in Data.prefix(upTo:).
• Documentation updates:
  • Fixed an outdated example in README (PR #4 by @brianantonelli).
  • Fixed grammar issues related to the usage of articles, during/while, and others.
• swcomp changes:
  • Minimum required version of SwiftCLI is now 5.2.0.
  • Improved the layout of output of benchmark commands.

• Added LZMAProperties struct with simple member-wise initializer.
• Added LZMA.decompress(data:properties:uncompressedSize:) function (with uncompressedSize argument being optional) which allows to specify LZMA properties.
  • Useful in situations when properties are known from some external source instead of being encoded at the beginning of data.
  • Note, that these new APIs are intended to be used by expert users and as such no validation is performed on LZMA properties values.
• Added support for Delta "filter" in both XZ archives and 7-Zip containers.
• Added support for SHA-256 check type in XZ archives.
  • As a result XZError.checkTypeSHA256 is now never thrown and will be removed in the next major update.
• Added ZipEntryInfo.crc property.
• Fixed a problem where XZArchive.unarchive and XZArchive.splitUnarchive functions would produce incorrect result when more than one "filter" was used (though it was practically impossible to encounter this issue since only one filter was supported (LZMA2) until this update).
• Reduced in-memory size of ZipEntryInfo instances.
  • Some rough estimates indicate that the reduction is up to 68%.
• Clarified documentation for LZMA.decompress(data:) to explain expectation about data argument.
  • Particularly, it is explained that it expects LZMA properties encoded with standard LZMA encoding scheme at the beginning of data.
• swcomp changes:
  • zip -i command now also prints CRC32 for all entries.
  • -v is now accepted as an alias for --verbose option.

This is the first and only test release for the upcoming 4.5.0 update. It includes new LZMAProperties APIs, support for SHA-256 check for XZ archives and support for delta filter in 7-ZIP and XZ, as well as a couple of fixes.

Known issue: no documentation for new APIs.

A couple of side notes before diving into release notes:

1. I've started a github project board where I am going to track and plan changes and additions for 5.0 Update.
2. If you ever wanted to financially support either this project or me you can now do so using this link.

Creating TAR containers

The main addition in this update is a set of APIs which allow to create a new TAR container.

• Added TarContainer.create(from:) function which creates a new TAR container with provided array of TarEntry objects as its content and generates container's Data.
• Added TarCreateError error type with a single case utf8NonEncodable. Comment: This enum is planned to be merged with TarError in 5.0. A new enum had to be created since otherwise it would be a breaking change to introduce a new case to already existing enum.

To enable reasonable usage scenarios for these new APIs, additional changes to existing APIs have been made:

• TarEntry.info and TarEntry.data are now var-properties (instead of let).
• Accessing setter of TarEntry.data now automatically updates TarEntry.info.size with data.count value (or 0 if data is nil). Comment: Maintaining consistency between these two properties is extremely important for producing correct and valid containers.
• Added (or, rather, made public) TarEntry.init(info:data:) initializer.
• Most public properties of TarEntryInfo are now var-properties (instead of let). Exceptions: size and type. Comment: Property size is kept read-only for reasons mentioned above. The reason for not allowing mutating type property is more vague: it is hard to imagine usage scenario where changing the type of an entry makes sense. Moreover, there are some concerns about (potential future) behavior in more generic context with type-erased ContainerEntryInfo objects, etc.
• Added TarEntryInfo.init(name:type:) initializer.

I do realize that this set of APIs is somewhat limited. For example, it is not easy to convert ZIP container (array of ZipEntry objects) to TAR using these new additions. But rest assured, there are plans to provide more generic functionality for creating new containers in the future (something like TarContainer.create(from entries: [ContainerEntry]) throws -> Data).

Other Changes

• Improved compatibility with other TAR implementations:
  • All string fields of TAR headers are now treated as UTF-8 strings. Comment: This is compatible with previous behavior since ASCII strings are UTF-8 strings.
  • Non-well-formed numeric fields of TAR headers no longer cause TarError.wrongField to be thrown and instead result in nil values of corresponding properties of TarEntryInfo (exception: size field). Comment: Mainly, this change was made to accommodate situations when a TAR header field is absent (i.e. filled with NULLs). Absent size field is still not accepted since its value impacts the structure of the container. This particular behavior is consistent with other implementations.
  • Base-256 encoding of numeric fields, which is sometimes used for very big or negative values, is now supported.
  • Leading NULLs and whitespaces in numeric fields are now correctly skipped.
  • Sun Extended Headers are now processed as local PAX extended headers instead of being considered entries with .unknown type.
  • GNU TAR format features for incremental backups are now partially supported (access and creation time).
• TarContainer.formatOf now correctly returns TarFormat.gnu when GNU format "magic" field is encountered.
• A new (copy) Data object is now created for TarEntry.data property instead of using a slice of input container data. Comment: This change makes indices of TarEntry.data zero-based which is consistent with other containers. This should also prevent keeping in memory Data for the entire container until the TarEntry object is destroyed.
• Fixed incorrect file name of TAR entries from containers with GNU TAR format-specific features being used.
• Fixed TarError.wrongPaxHeaderEntry error being thrown when header with multi-byte UTF-8 characters is encountered.
• Fixed incorrect values of TarEntryInfo.ownerID, groupID, deviceMajorNumber and deviceMinorNumber properties (previously, they were assumed to be encoded as decimal numbers).
• Slightly improved performance of LZMA/LZMA2 operations by making internal classes declared as final.
• swcomp changes:
  • Added -c, --create option to tar command which creates a new TAR container.
  • Output of bencmark commands is now properly flushed on non-Linux platforms.
  • Results for omitted iterations of benchmark commands are now also printed.
  • Iteration number in benchmark commands is now printed with leading zeros.
  • Fixed compilation error on Linux platforms due to ObjCBool no longer being an alias for Bool.

This is the first and only test release for the upcoming 4.4.0 update. It includes functionality for creating new TAR containers as well as numerous fixes for TAR open/info functions.

Known issue: no documentation for new APIs.