crcengine package

Module contents

Package exports

exception crcengine.AlgorithmNotFoundError

Bases: Exception

Exception raised when an unrecognized algorithm is requested.

class crcengine.CrcParams(polynomial: int, width: int, seed: int, reflect_in: bool, reflect_out: bool, xor_out: int)

Bases: NamedTuple

Basic parameters for specifying a CRC algorithm

polynomial: int

Alias for field number 0

reflect_in: bool

Alias for field number 3

reflect_out: bool

Alias for field number 4

seed: int

Alias for field number 2

validate() → None

raise an InvalidParametersError if the specified CRC parameters are not mutually consistent

width: int

Alias for field number 1

xor_out: int

Alias for field number 5

crcengine.algorithms_available() → Iterable[str]

Obtain an iterable of available named CRC algorithms

crcengine.available_calculation_engines() → Iterable[str]

Return the list of available calculation back-ends. These can be used with crcengine.create()

crcengine.bit_reverse_byte(byte: int) → int

Bit-bashing reversal of a byte

crcengine.bit_reverse_n(value: int, num_bits: int) → int

Mirror the bits in an integer

Parameters:

  • value – the integer to reverse

  • num_bits – the number of bits to reverse

Returns:

mirrored value

crcengine.create(poly=None, width=None, seed=None, ref_in=True, ref_out=True, name='', xor_out=16777215, params: Optional[CrcParams] = None, calc_engine='table')

Create a table-driven CRC calculation engine

Parameters:

  • poly – polynomial (deprecated)

  • width – polynomial width in bits (deprecated)

  • seed – seed value for the CRC calculation to use (deprecated)

  • ref_in – reflect input bits (deprecated)

  • ref_out – reflect output bits (deprecated)

  • name – associate a name with this algorithm (deprecated)

  • xor_out – exclusive-or the output with this value (deprecated)

  • params – CRC parameters, same as specifying individual parameters

  • calc_engine – back-end calculation engine to use

Returns:

crcengine.create_from_params(params: CrcParams, calc_engine='table')

Create a CRC calculation algorithm instance based on params using calculation engine calc_engine as the back end

Parameters:

  • params –

  • calc_engine –

Returns:

crcengine.create_generic(poly: int, width: int, seed: int, ref_in: bool, ref_out: bool, xor_out: int, name='')

Create generic non-table-driven CRC calculator

Parameters:

  • poly – Polynomial

  • width – calculator width in bits e.g. 32

  • seed – calculation seed value

  • ref_in – reflect incoming bits

  • ref_out – reflect result bits

  • name – name to assign to calculator

  • xor_out – pattern to XOR into result

Returns:

A CRC calculation engine

crcengine.create_lsb_table(poly, width)

Calculate a CRC lookup table for the selected algorithm definition producing a table that can be used for the lsbit algorithm

Returns:

table of reflected

crcengine.create_msb_table(poly, width)

Calculate a CRC lookup table for the selected algorithm definition :return: list of CRC values

crcengine.generate_code(crc_name_params, output_dir='out/', language='C', seed_parameter=False, func_name=None)

Generate code implementing a specific CRC. Currently only language=C is supported

crcengine.generate_test(name, output_dir)

Generate a Ceedling C-test wrapper for a given algorithm’s generated code

Parameters:

  • name – name of algorithm

  • output_dir – directory into which output should be written

Returns:

crcengine.generic_crc(params: CrcParams)

Return a general-purpose MSB-first CRC algorithm

Parameters:

params – CRC algorithm parameters

Returns:

CRC algorithm

crcengine.get_algorithm_params(name: str, include_check=False) → Dict[str, Union[str, int, bool]]

Obtain the parameters for a named CRC algorithm Optionally the ‘check’ field can be included, this field is not part of the definition of the algorithm and so is omitted by default

Parameters:

  • name – Name of algorithm (lowercase)

  • include_check – if True include the ‘check’ field in the output

Returns:

dict of algorithm parameters

Raises:

AlgorithmNotFoundError if algorithm with name cannot be found

crcengine.get_bits_max_value(nbits)

Convenience function returning largest unsigned integer for a given number of bits

crcengine.lookup_params(name: str) → CrcParams

Look up CRC parameters given an algorithm name. A list of algorithms can be obtained using algorithms_available()

Parameters:

name – name of CRC algorithm

Raises:

AlgorithmNotFoundError – if algorithm name cannot be found

crcengine.new(name: str, calc_engine='table')

Create a new CRC calculation instance

crcengine.register_algorithm(name, polynomial, width, seed, reflect, xor_out, check=0)

Register a CRC algorithm with custom parameters

crcengine.register_algorithm_params(name: str, params: CrcParams, check=None) → None

Register a CRC algorithm with custom parameters

crcengine.table_crc(params: CrcParams)

Return a table-based CRC algorithm corresponding to params

crcengine.unregister_algorithm(name: str) → None

Remove an algorithm registration

Submodules

crcengine.codegen module

Generation of C code for CRC calculation

crcengine.codegen.generate_code(crc_name_params, output_dir='out/', language='C', seed_parameter=False, func_name=None)

Generate code implementing a specific CRC. Currently only language=C is supported

crcengine.codegen.generate_test(name, output_dir)

Generate a Ceedling C-test wrapper for a given algorithm’s generated code

Parameters:

  • name – name of algorithm

  • output_dir – directory into which output should be written

Returns:

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