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# Lead Maintainer: Virgil Security Inc. <support@virgilsecurity.com>


from ctypes import *
from ._c_bridge import VscfPaddingParams


class PaddingParams(object):
    """Handles padding parameters and constraints."""

    DEFAULT_FRAME_MIN = 32
    DEFAULT_FRAME = 160
    DEFAULT_FRAME_MAX = 256

    def __init__(self):
        """Create underlying C context."""
        self._lib_vscf_padding_params = VscfPaddingParams()
        self.ctx = self._lib_vscf_padding_params.vscf_padding_params_new()

    def __delete__(self, instance):
        """Destroy underlying C context."""
        self._lib_vscf_padding_params.vscf_padding_params_delete(self.ctx)

    @classmethod
    def with_constraints(cls, frame, frame_max):
        """Build padding params with given constraints.
        Next formula can clarify what frame is: padding_length = data_length MOD frame"""
        inst = cls.__new__(cls)
        inst._lib_vscf_padding_params = VscfPaddingParams()
        inst.ctx = inst._lib_vscf_padding_params.vscf_padding_params_new_with_constraints(frame, frame_max)
        return inst

    def frame(self):
        """Return padding frame in bytes."""
        result = self._lib_vscf_padding_params.vscf_padding_params_frame(self.ctx)
        return result

    def frame_max(self):
        """Return maximum padding frame in bytes."""
        result = self._lib_vscf_padding_params.vscf_padding_params_frame_max(self.ctx)
        return result

    @classmethod
    def take_c_ctx(cls, c_ctx):
        inst = cls.__new__(cls)
        inst._lib_vscf_padding_params = VscfPaddingParams()
        inst.ctx = c_ctx
        return inst

    @classmethod
    def use_c_ctx(cls, c_ctx):
        inst = cls.__new__(cls)
        inst._lib_vscf_padding_params = VscfPaddingParams()
        inst.ctx = inst._lib_vscf_padding_params.vscf_padding_params_shallow_copy(c_ctx)
        return inst
