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(lib)unarr

(lib)unarr is a decompression library for RAR, TAR, ZIP and 7z* archives.

It was forked from unarr, which originated as a port of the RAR extraction features from The Unarchiver project required for extracting images from comic book archives. Zeniko wrote unarr as an alternative to libarchive which didn't have support for parsing filters or solid compression at the time.

While (lib)unarr was started with the intent of providing unarr with a proper cmake based build system suitable for packaging and cross-platform development, it's focus has now been extended to provide code maintenance and to continue the development of unarr, which no longer is maintained.

Getting started

Building from source

Dependencies

(lib)unarr can take advantage of the following libraries if they are present:

  • bzip2
  • xz / libLZMA
  • zlib

More information on what library is used for which purpose can be found in the description for embedded builds.

Cmake

mkdir build
cd build
cmake ..
make

... as a static library

cmake .. -DBUILD_SHARED_LIBS=OFF

Install

make install

Embedded build

Make sure your compiler is C99 compatible, grab the source code, copy it into your project and adjust your build system accordingly.

You can define the following symbols to take advantage of third party libraries:

Symbol Required header Required for (format/method)
HAVE_ZLIB zlib.h faster CRC-32 and Deflate
HAVE_BZIP2 bzlib.h ZIP / Bzip2
HAVE_LIBLZMA lzma.h ZIP / LZMA, XZ(LZMA2)
HAVE_7Z 7z.h 7Z* / LZMA, LZMA2, BCJ
_7ZIP_PPMD_SUPPORT 7Z* / PPMd

Make sure the required headers are present in the include path.

Usage

Examples

Check unarr.h and unarr-test to get a general feel for the api and usage.

Limitations

Unarr was written for comic book archives, so it currently doesn't support:

  • password protected archives
  • self extracting archives
  • split archives

7z support

7z support is currently broken. This is due to two problems:

  1. The version of the LZMA SDK used in the 7z extraction code is outdated and no longer compatible with the LZMA code used in the other formats
  2. The ANSI-C based 7z extraction code provided by the LZMA SDK has a known performance issue that limits it's usefullness for large files with solid compression (see zeniko/unarr#4).

Fixing these problems requires a partial rewrite of the code involved.