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SABCTools - C implementations of functions for use within SABnzbd

This module implements three main sets of C implementations that are used within SABnzbd:

  • yEnc decoding and encoding using SIMD routines
  • CRC32 calculations
  • Non-blocking SSL-socket reading
  • Marking files as sparse

Of course, they can also be used in any other application.

yEnc decoding and encoding using SIMD routines

yEnc decoding and encoding performed by using yencode from animetosho,
which utilizes x86/ARM SIMD optimised routines if such CPU features are available.

CRC32 calculations

We used the crcutil library for very fast CRC calculations.

Non-blocking SSL-socket reading

When Python reads data from a non-blocking SSL socket, it is limited to receiving 16K data at once. This module implements a patched version that can read as much data is available at once. For more details, see the cpython pull request.

Marking files as sparse

Uses Windows specific system calls to mark files as sparse and set the desired size. On other platforms the same is achieved by calling truncate.


As simple as running:

pip install sabctools --upgrade  

When you want to compile from sources, you can run in the sabctools directory:

pip install .  

SIMD detection

To see which SIMD set was detected on your system, run:

python -c "import sabctools; print(sabctools.simd);"  

OpenSSL detection

To see if we could link to OpenSSL library on your system, run:

python -c "import sabctools; print(sabctools.openssl_linked);"  


For testing we use pytest (install via pip install -r tests/requirements.txt) and test can simply be executed by browsing to the sabctools directory and running:


Note that tests can fail if git modified the line endings of data files when checking out the repository!