CRC

class baseband.vlbi_base.utils.CRC(polynomial)

Bases: object

Cyclic Redundancy Check for a bitstream.

See https://en.wikipedia.org/wiki/Cyclic_redundancy_check

Once initialised, the instance can be used as a function that calculates the CRC, or one can use the check method to verify that the CRC at the end of a stream is correct.

Parameters

polynomialint

Binary encoded CRC divisor. For instance, that used by Mark 4 headers is 0x180f, or x^12 + x^11 + x^3 + x^2 + x + 1.

Methods Summary

__call__(self, stream)	Calculate CRC for the given stream.
check(self, stream)	Check that the CRC at the end of the stream is correct.

Methods Documentation

__call__(self, stream)

Calculate CRC for the given stream.

Parameters

streamarray of bool or unsigned int

The dimension is treated as the index into the bits. For a single stream, the array should thus be of type bool. Integers represent multiple streams. E.g., for a 64-track Mark 4 header, the stream would be an array of np.uint64 words.

Returns

crcarray

The crc will have the same dtype as the input stream.

check(self, stream)

Check that the CRC at the end of the stream is correct.

Parameters

streamarray of bool or unsigned int

The dimension is treated as the index into the bits. For a single stream, the array should thus be of type bool. Integers represent multiple streams. E.g., for a 64-track Mark 4 header, the stream would be an array of np.uint64 words.

Returns

okbool

True if the calculated CRC is all zero (which should be the case if the CRC at the end of the stream is correct).