Source code for zserio.serialization

"""
The module provides help methods for serialization and deserialization of generated objects.
"""

import typing

from zserio.bitwriter import BitStreamWriter
from zserio.bitbuffer import BitBuffer
from zserio.bitreader import BitStreamReader


def serialize(obj: typing.Any) -> BitBuffer:
    """
    Serializes generated object to the bit buffer.

    Before serialization, the method calls initialize_offsets() on the given zserio object.

    Because serialization to the bit buffer does not have to be byte aligned (divisible by 8), it's possible
    that not all bits of the last byte are used. In this case, only most significant bits of the corresponded
    size are used.

    Example:

    .. code:: python

        import zserio

        obj = SomeZserioObject()
        bitbuffer = zserio.serialize(obj)

    :param obj: Generated object to serialize.
    :returns: Bit buffer which represents generated object in binary format.
    :raises PythonRuntimeException: Throws in case of any error during serialization.
    """

    writer = _serialize(obj)

    return BitBuffer(writer.byte_array, writer.bitposition)


def deserialize(obj_class: typing.Type[typing.Any], bitbuffer: BitBuffer, *args) -> typing.Any:
    """
    Deserializes bit buffer to the generated object.

    Example:

    .. code:: python

        import zserio

        bitbuffer = zserio.BitBuffer(b'\\x00\\x01\\xBD\\x5A', 31)
        obj = zserio.deserialize(SomeZserioObject, bitbuffer, 0xAB)

    :param obj_class: Class instance of the generated object to deserialize.
    :param bitbuffer: Bit buffer which represents generated object in binary format.
    :param args: Additional arguments needed for obj_class.from_reader method.
    :returns: Generated object created from given bit buffer.
    :raises PythonRuntimeException: Throws in case of any error during deserialization.
    """

    reader = BitStreamReader.from_bitbuffer(bitbuffer)

    return obj_class.from_reader(reader, *args)


def serialize_to_bytes(obj: typing.Any) -> bytes:
    """
    Serializes generated object to the byte buffer.

    Before serialization, the method calls initialize_offsets() on the given zserio object.

    This is a convenient method for users which do not need exact number of bits to which the given object
    will be serialized.

    However, it's still possible that not all bits of the last byte are used. In this case, only most
    significant bits of the corresponding size are used.

    Example:

    .. code:: python

        import zserio

        obj = SomeZserioObject()
        buffer = zserio.serialize_to_bytes(obj)

    :param obj: Generated object to serialize.
    :returns: Bytes which represents generated object in binary format.
    :raises PythonRuntimeException: Throws in case of any error during serialization.
    """

    writer = _serialize(obj)

    return writer.byte_array


def deserialize_from_bytes(obj_class: typing.Type[typing.Any], buffer: bytes, *args) -> typing.Any:
    """
    Deserializes byte buffer to the generated object.

    This method can potentially use all bits of the last byte even if not all of them were written during
    serialization (because there is no way how to specify exact number of bits). Thus, it could allow reading
    behind stream (possibly in case of damaged data).

    Example:

    .. code:: python

        import zserio

        buffer = b'\\x00\\x01\\xBD\\x5A'
        obj = zserio.deserialize_from_bytes(SomeZserioObject, buffer, 0xAB)

    :param obj_class: Class instance of the generated object to deserialize.
    :param buffer: Byte buffer which represents generated object in binary format.
    :param args: Additional arguments needed for obj_class.from_reader method.
    :returns: Generated object created from given byte buffer.
    :raises PythonRuntimeException: Throws in case of any error during deserialization.
    """

    bitbuffer = BitBuffer(buffer)

    return deserialize(obj_class, bitbuffer, *args)


def serialize_to_file(obj: typing.Any, filename: str) -> None:
    """
    Serializes generated object to the file.

    Before serialization, the method calls initialize_offsets() on the given zserio object.

    This is a convenient method for users to easily write given generated object to file.

    Example:

    .. code:: python

        import zserio

        obj = SomeZserioObject()
        buffer = zserio.serialize_to_file(obj, "file_name.bin")

    :param obj: Generated object to serialize.
    :param filename: File to write.
    :raises PythonRuntimeException: Throws in case of any error during serialization.
    """

    writer = _serialize(obj)
    writer.to_file(filename)


def deserialize_from_file(obj_class: typing.Type[typing.Any], filename: str, *args) -> typing.Any:
    """
    Deserializes file to the generated object.

    This is a convenient method for users to easily read given generated object from file.

    Example:

    .. code:: python

        import zserio

        obj = zserio.deserialize_from_file(SomeZserioObject, "file_name.bin", 0xAB)

    :param obj_class: Class instance of the generated object to deserialize.
    :param filename: File which represents generated object in binary format.
    :param args: Additional arguments needed for obj_class.from_reader method.
    :returns: Generated object created from given file contents.
    :raises PythonRuntimeException: Throws in case of any error during deserialization.
    """

    reader = BitStreamReader.from_file(filename)

    return obj_class.from_reader(reader, *args)


def _serialize(obj: typing.Any) -> BitStreamWriter:
    writer = BitStreamWriter()
    obj.initialize_offsets(writer.bitposition)
    obj.write(writer)

    return writer