Padding Arithmetic

pcapkit.corekit.schema.padding counts the octets of padding that take a length to a boundary, for the padding fields, the schemas’ length callbacks, the protocols’ makers and the capture engines alike. It is one of the pcapkit.corekit.schema helpers shared across the schema layer, not part of the header schema framework in pcapkit.protocols.schema; see Choosing Between utilities and corekit.

Added in version 1.6.0.

pcapkit.corekit.schema.padding.pad_length(length, align)

Octets of padding that take length octets to an align-octet boundary.

Parameters:

• length (int) – Octets to be padded.

• align (int) – Boundary, in octets.

Returns:

from 0, where length is already a multiple of align, to align - 1.

Return type:

int

Raises:

• IntError – If align is not an int, or is a bool.

• FieldValueError – If align is not positive.

A schema’s length callbacks are handed the packet data, not a protocol, so this is a plain function and not a protocol method. PaddingField sizes itself by it when given align.

Added in version 1.6.0.