bpack.descriptors module

Descriptors for binary records.

class bpack.descriptors.BinFieldDescriptor(type: Optional[Type] = None, size: Optional[int] = None, offset: Optional[int] = None, signed: Optional[bool] = None, repeat: Optional[int] = None)[source]

Bases: object

Descriptor for bpack fields.

is_enum_type() bool[source]
is_int_type() bool[source]
is_sequence_type() bool[source]
update_from_type(type_: Type)[source]
validate()[source]

Perform validity check on the BinFieldDescriptor instance.

offset: Optional[int] = None
repeat: Optional[int] = None
signed: Optional[bool] = None
size: Optional[int] = None
property total_size

Total size in bytes of the field (considering all item).

type: Optional[Type] = None
class bpack.descriptors.Field(default, default_factory, init, repr, hash, compare, metadata)[source]

Bases: object

compare
default
default_factory
hash
init
metadata
name
repr
type
bpack.descriptors.asdict(obj, *, dict_factory=<class 'dict'>) dict[source]

Return the fields of a record as a new dictionary.

The returned dictionary maps field names to field values.

If given, ‘dict_factory’ will be used instead of built-in dict. The function applies recursively to field values that are dataclass instances. This will also look into built-in containers: tuples, lists, and dicts.

bpack.descriptors.astuple(obj, *, tuple_factory=<class 'tuple'>) Sequence[source]

Return the fields of a dataclass instance as a new tuple of field values.

If given, ‘tuple_factory’ will be used instead of built-in tuple. The function applies recursively to field values that are dataclass instances. This will also look into built-in containers: tuples, lists, and dicts.

bpack.descriptors.baseunits(obj) bpack.enums.EBaseUnits[source]

Return the base units of a binary record descriptor.

bpack.descriptors.bitorder(obj) Optional[bpack.enums.EBitOrder][source]

Return the bit order of a binary record descriptor.

bpack.descriptors.byteorder(obj) bpack.enums.EByteOrder[source]

Return the byte order of a binary record descriptor (endianess).

bpack.descriptors.calcsize(obj, units: Optional[bpack.enums.EBaseUnits] = None) int[source]

Return the size of the obj record.

If the units parameter is not specified (default) then the returned size is expressed in the same base units of the descriptor.

bpack.descriptors.descriptor(cls, *, size: Optional[int] = None, byteorder: Union[str, bpack.enums.EByteOrder] = EByteOrder.DEFAULT, bitorder: Optional[Union[str, bpack.enums.EBitOrder]] = None, baseunits: bpack.enums.EBaseUnits = EBaseUnits.BYTES, **kwargs)[source]

Class decorator to define descriptors for binary records.

It converts a dataclass into a descriptor object for binary records.

  • ensures that all fields are bpack.descriptor.Field descriptors

  • offsets are automatically computed if necessary

  • consistency checks on offsets and sizes are performed

Parameters

It is also possible to specify as additional keyword arguments all the parameters accepted by dataclasses.dataclass().

bpack.descriptors.field(*, size: Optional[int] = None, offset: Optional[int] = None, signed: Optional[bool] = None, repeat: Optional[int] = None, metadata=None, **kwargs) dataclasses.Field[source]

Initialize a field descriptor.

Returned object is a Field instance with metadata properly initialized to describe the field of a binary record.

bpack.descriptors.field_descriptors(descriptor, pad: bool = False) Iterable[bpack.descriptors.BinFieldDescriptor][source]

Return the list of field descriptors for the input record descriptor.

Items are instances of the BinFieldDescriptor class describing characteristics of each field of the input binary record descriptor.

If the pad parameter is set to True then also generate dummy field descriptors for padding elements necessary to take into account offsets between fields.

bpack.descriptors.fields(obj) Sequence[dataclasses.Field][source]

Return a tuple describing the fields of this descriptor.

bpack.descriptors.get_field_descriptor(field: dataclasses.Field, validate: bool = True) bpack.descriptors.BinFieldDescriptor[source]

Return the field descriptor attached to a Field.

bpack.descriptors.is_descriptor(obj) bool[source]

Return true if obj is a descriptor or a descriptor instance.

bpack.descriptors.is_field(obj) bool[source]

Return true if an obj can be considered is a field descriptor.

bpack.descriptors.set_field_descriptor(field: dataclasses.Field, descriptor: bpack.descriptors.BinFieldDescriptor, validate: bool = True) dataclasses.Field[source]

Set the field metadata according to the specified descriptor.