.. role:: raw-latex(raw)
   :format: latex
..

Auxiliary Libraries
===================

The Yosys source distribution contains some auxiliary libraries that are
bundled with Yosys.

SHA1
----

The files in ``libs/sha1/`` provide a public domain SHA1 implementation
written by Steve Reid, Bruce Guenter, and Volker Grabsch. It is used for
generating unique names when specializing parameterized modules.

BigInt
------

The files in ``libs/bigint/`` provide a library for performing
arithmetic with arbitrary length integers. It is written by Matt
McCutchen .

The BigInt library is used for evaluating constant expressions,
e.g. using the ``ConstEval`` class provided in ``kernel/consteval.h``.

.. _sec:SubCircuit:

SubCircuit
----------

The files in ``libs/subcircuit`` provide a library for solving the
subcircuit isomorphism problem. It is written by Clifford Wolf and based
on the Ullmann Subgraph Isomorphism Algorithm
:raw-latex:`\cite{UllmannSubgraphIsomorphism}`. It is used by the
``extract`` pass (see ``help extract`` or
Sec. `[cmd:extract] <#cmd:extract>`__).

ezSAT
-----

The files in ``libs/ezsat`` provide a library for simplifying generating
CNF formulas for SAT solvers. It also contains bindings of MiniSAT. The
ezSAT library is written by Clifford Wolf. It is used by the ``sat``
pass (see ``help sat`` or Sec. `[cmd:sat] <#cmd:sat>`__).