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 check that the CRC at the end of a stream is correct.

Parameters:

polynomial : int

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

Methods Documentation

__call__(stream)

Calculate CRC for the given stream.

Parameters:

stream : array 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:

crc : array

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

check(stream)

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

Parameters:

stream : array 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:

ok : bool

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