cypyserialize 1.0.4
Really easy, really quick, binary parser framework for Python
License: Apache 2.0
Keywords: testing,logging,example

SerializableObject
==================

A pythonic semantic for describing binary data structures and associated
python objects.

Installation
------------

::

    pip install cypyserialize

Basic Usage
-----------

For this first example we're going to define a simple 2D point with the
attributes ``x`` and ``y`` representing binary doubles.

.. code:: python

    class Point(cypyserialize.SerializableObject):
        "Basic point class"
        x = cypyserialize.double()
        y = cypyserialize.double()

Object instances of the ``Point`` class, which extends the
``SerializableObject``, can be initialized in several different ways.
First, omitting any parameters the instance will be populated with
default values (here we haven't specified defaults so 0.0 is assumed).
The attributes can be assigned values after initialization.

.. code:: python

    >>> p = Point() # create default instance
    >>> list(p.items())
    [('x', None), ('y', None)]
    >>> p.x = 5000.0 # set x
    >>> p.y = 300.5 # set y
    >>> list(p.items())
    [('x', 5000.0), ('y', 300.5)]

Alternately, the object can be initialized with our values. The
parameter order should match the order specified in the class attribute
``_field_order``.

.. code:: python

    >>> p = Point(5000.0, 300.5)
    >>> list(p.items())
    [('x', 5000.0), ('y', 300.5)]

Or we can use the attribute names if we forgot the order.

.. code:: python

    >>> p = Point(y=300.5, x=5000.0)
    >>> list(p.items())
    [('x', 5000.0), ('y', 300.5)]

Or mix the two (just remeber that after the first named parameter
subsequent parameters will have to be named as well).

.. code:: python

    >>> p = Point(5000.0, y=300.5)
    >>> list(p.items())
    [('x', 5000.0), ('y', 300.5)]

To get the binary representation just call the class method ``pack``

.. code:: python

    >>> p.pack()
    bytearray(b'\x00\x00\x00\x00\x00\x88\xb3@\x00\x00\x00\x00\x00\xc8r@')

Lastly, we can initialize with a binary string.

.. code:: python

    >>> p = Point(b'\x00\x00\x00\x00\x00\x88\xb3@\x00\x00\x00\x00\x00\xc8r@')
    >>> list(p.items())
    [('x', 5000.0), ('y', 300.5)]

Using Substructures
-------------------

We're going to reuse the ``Point`` class to describe a rectangular
bounding box with two attributes, the northwest and southeast corners.

.. code:: python

    class BoundingBox(cypyserialize.SerializableObject):
        northwest = Point()
        southeast = Point()

Seriously, it's that easy. Let's initialize one of these.

.. code:: python

    >>> bb = BoundingBox()
    >>> list(bb.items())
    [('northwest', <Point object>), ('southeast',  <Point object>)]

Let's try that again but with some points

.. code:: python

    >>> bb = BoundingBox(Point(0.0, 10.0), Point(15.0, 0.0))
    >>> bb.northwest.y
    10.0
    >>> bb.southeast.x
    15.0

Overloading
-----------

Subclasses of SerializableObject can be extended and overloaded. This
can be especially handy if you have a standard structure that you don't
want to redefine.

Here we're going to make a simple datagram structure with a start and
end flag, a timestamp and some arbitrary body that we'll overload in a
second.

.. code:: python

    class GenericDatagram(cypyserialize.SerializableObject):
        STX = cypyserialize.uchar(value=0x02)
        timestamp = cypyserialize.uint()
        body = cypyserialize.none()
        ETX = cypyserialize.uchar(value=0x03)

Now that we have generic datagram lets make it a wrapper on the
BoundingBox structure we defined earlier as an extension of the
GenericDatagram structure.

.. code:: python

    class BoundingBoxDatagram(GenericDatagram):
        body = BoundingBox()

That's it. Lets create one of this. We'll set the timestamp and get the
binary.

.. code:: python

    >>> p = BoundingBoxDatagram()
    >>> p.timestamp = time.time()
    >>> p.body = BoundingBox(Point(0, 10), Point(10, 0))
    >>> p.items()
    [('STX', 2), ('timestamp', 1398373100.412985), ('body', <__main__.BoundingBox object at 0xb713f3c4>), ('ETX', 3)]
    >>> p.pack()
    '\x02...'

Arrays of Substructures
-----------------------

Now we're going to reuse the point structure to describe a path as a
series of points with a description.

.. code:: python

    class Path(cypyserialize.SerializableObject):
        # the points
        points = cypyserialize.SerializableArray(
            Point(),
            count=cypyserialize.uint()
        )

``count`` with be the field type that is used to read and write the
number of ``Point()`` objects in the structure.

Byte Order
----------

***Currently Unsupported***

Byte order is always little endian at present.

Custom Computed Attributes
--------------------------

.. code:: python

    class BetterBoundingBox(BoundingBox):
        def __init__(self):
            self.area = (self.southeast.x - self.northwest.x) * \
                        (self.northwest.y - self.southeast.y)

Note that we need to accept ``args`` and ``kargs``, we don't need to
call the superclass **init** though as it wasn't defined on BoundingBox.

Lets try it out.

.. code:: python

    >>> bb = BetterBoundingBox(Point(0,10),Point(10,0))
    >>> print bb.area
    100