binfield

Python binfield implementation for binary data manipulation.

Why? Python supports binary data manipulation via binary operations out of the box and it's fast, but it's hard to read and painful during prototyping, especially for complex (nested) structures.

This library is designed to fix this issue: it allows to operate with binary data like dict with constant indexes: you just need to define structure class and create an instance with start data. Now you can use indexes for reading and writing data

Pros:

• Free software: Apache license
• Open Source: https://github.com/penguinolog/binfield
• Self-documented code: docstrings with types in comments
• Tested: see badges on top
• Support multiple Python versions:

Python 3.6
Python 3.7
PyPy3

Usage

Not mapped objects can be created simply from BinField class:

bf = BinField(42)

Data with fixed size should be created as a new class (type): Example on real data (ZigBee frame control field):

# Describe
class ZBFrameControl(binfield.BinField):
    _size_ = 16  # Optional, used as source for mask, if mask is not defined
    _mask_ = 0xFF7F  # Optional, used as source for size, if size is not defined
    FrameType = [0, 3]  # Enum
    Security = 3
    FramePending = 4
    AckRequest = 5
    PAN_ID_Compression = 6
    SecurityNumberSuppress = 8
    InformationPresent = 9
    DstAddrMode = [10, 12]
    FrameVersion =  [12, 14]
    SrcAddrMode = [14, 16]

# Construct from frame
# (limitation: endian conversion is not supported, make it using another tools)
frame = frame = ZBFrameControl(0x0803)  # Beacon request

>>> print(frame)
<2051 == 0x0803 == (0b0000100000000011 & 0b1111111111111111)
  FrameType             = <3 == 0x03 == (0b011 & 0b111)>
  Security               = <0 == 0x00 == (0b0 & 0b1)>
  FramePending           = <0 == 0x00 == (0b0 & 0b1)>
  AckRequest             = <0 == 0x00 == (0b0 & 0b1)>
  PAN_ID_Compression     = <0 == 0x00 == (0b0 & 0b1)>
  SecurityNumberSuppress = <0 == 0x00 == (0b0 & 0b1)>
  InformationPresent     = <0 == 0x00 == (0b0 & 0b1)>
  DstAddrMode            = <2 == 0x02 == (0b10 & 0b11)>
  FrameVersion           = <0 == 0x00 == (0b00 & 0b11)>
  SrcAddrMode            = <0 == 0x00 == (0b00 & 0b11)>

>>> repr(frame)
'ZBFrameControl(x=0x0803, base=16)'

>>> print(frame.FrameType)
<3 == 0x03 == (0b011 & 0b111)>  # Get nested structure: current is flat, so we have single value

# We can use slice to get bits from value: result type is always subclass of BinField
>>> repr(frame.FrameType[: 2])
'<FrameType_slice_0_2(x=0x03, base=16) at 0x7FD0ACA57408>'

>>> frame.FrameType == 3  # Transparent comparision with integers
True

>>> int(frame.FrameType)  # Painless conversion to int
3

>>> bool(frame.AckRequest)  # And bool
False

>>> print(frame[1: 5])  # Ignore indexes and just get few bits using slice
<1 == 0x01 == (0b0001 & 0b1111)>

>>> print(ZBFrameControl.AckRequest)  # Request indexes from created data type
5

>>> print(ZBFrameControl.DstAddrMode)  # Multiple bits too
slice(10, 12, None)

# Modification of nested data (if no type conversion was used) changes original object:
>>> frame.AckRequest = 1
>>> print(frame)
<2083 == 0x0823 == (0b0000100000100011 & 0b1111111101111111)
  FrameType              = <3 == 0x03 == (0b011 & 0b111)>
  Security               = <0 == 0x00 == (0b0 & 0b1)>
  FramePending           = <0 == 0x00 == (0b0 & 0b1)>
  AckRequest             = <1 == 0x01 == (0b1 & 0b1)>
  PAN_ID_Compression     = <0 == 0x00 == (0b0 & 0b1)>
  SecurityNumberSuppress = <0 == 0x00 == (0b0 & 0b1)>
  InformationPresent     = <0 == 0x00 == (0b0 & 0b1)>
  DstAddrMode            = <2 == 0x02 == (0b10 & 0b11)>
  FrameVersion           = <0 == 0x00 == (0b00 & 0b11)>
  SrcAddrMode            = <0 == 0x00 == (0b00 & 0b11)>
>

# But remember, that nested blocks has it's own classes
>>> repr(frame.DstAddrMode)
'<DstAddrMode(x=0x02, base=16) at 0x7FD0AD139548>'

>>> fr2 = ZBFrameControl(0xFFFF)
>>> repr(fr2)
'ZBFrameControl(x=0xFF7F, base=16)'  # Mask if applied, if defined

# Fields can be set only from integers
>>> frame.SrcAddrMode = fr2.SrcAddrMode
Traceback (most recent call last):
...
TypeError: BinField value could be set only as int

>>> repr(frame['FramePending'])  # __getitem__ and __setitem__ is supported
'<FramePending(x=0x00, base=16) at 0x7FD0ACAD3188>'

Nested structures are supported, if required. Definition example (not aligned with any real data):

class NestedMappedBinField(BinField):
    test_index = 0
    nested_block = {
        '_index_': (1, 6),
        'single_bit': 0,
        'multiple': (1, 3)
    }

>>> bf = NestedMappedBinField(0xFF)
# No _size_ and no _mask_ -> size is not limited,
# but indexes can not be changed after class creation
>>> print(bf)
<255 == 0xFF == (0b11111111)
  test_index   = <1 == 0x01 == (0b1 & 0b1)>
  nested_block =
    <31 == 0x1F == (0b11111 & 0b11111)
      single_bit = <1 == 0x01 == (0b1 & 0b1)>
      multiple   = <3 == 0x03 == (0b11 & 0b11)>
    >
>

# Get nested block: nested block is structured.
>>> print(bf.nested_block)
<31 == 0x1F == (0b11111 & 0b11111)
  single_bit = <1 == 0x01 == (0b1 & 0b1)>
  multiple   = <3 == 0x03 == (0b11 & 0b11)>
>

Note: negative indexes are not supported by design!

Testing

Main test mechanism for the package binfield uses tox. Test environments available:

pep8
py36
pypy3
pylint
docs

CI systems

For code checking several CI systems are used in parallel:

1. Travis CI: is used for checking: PEP8, pylint, bandit, installation possibility and unit tests. Also it publishes coverage on coveralls.
2. coveralls: is used for coverage display.

CD system

Travis CI: is used for package delivery on PyPI.