80 lines
2.5 KiB
Python
80 lines
2.5 KiB
Python
"""
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null_node.py
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Defines the NullNode class, a no-op singleton execution node used for open execution pins
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in the object diagram execution graph.
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"""
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from abc import ABC
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from typing import List, Type
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from jinja2 import Template
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from api.od import ODAPI
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from .funcs import generate_dot_node
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from .singleton import Singleton
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from .exec_node import ExecNode
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class NullNode(ExecNode, metaclass=Singleton):
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"""
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A no-op execution node representing a null operation.
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This node is typically used to represent a placeholder or open execution pin.
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It always returns a fixed result and does not perform any operation.
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"""
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def __init__(self):
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"""
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Initializes the NullNode instance.
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Inherits unique ID and state behavior from ExecNode.
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"""
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super().__init__()
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def execute(self, port: str, exec_id: int, od: ODAPI) -> tuple[int, any] | None:
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"""
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Simulates execution by returning a static result indicating an open pin.
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Args:
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port (str): The name of the input port.
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exec_id (int): The current execution ID.
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od (ODAPI): The Object Diagram API instance providing execution context.
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Returns:
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tuple[int, str] | None: A tuple (-1, "open pin reached") indicating a no-op.
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"""
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return -1, "open pin reached"
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@staticmethod
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def get_exec_output_gates():
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"""
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Returns the list of output gates for execution.
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Returns:
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list: An empty list, as NullNode has no output gates.
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"""
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return []
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def generate_dot(
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self, nodes: List[str], edges: List[str], visited: set[int], template: Template
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) -> None:
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"""
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Generates DOT graph representation for this node if it hasn't been visited.
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Args:
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nodes (List[str]): A list to accumulate DOT node definitions.
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edges (List[str]): A list to accumulate DOT edge definitions.
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visited (set[int]): Set of already visited node IDs to avoid cycles.
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template (Template): A Jinja2 template used to render the node's DOT representation.
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"""
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if self.id in visited:
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return
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generate_dot_node(
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self,
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nodes,
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template,
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**{
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"label": "null",
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"ports_exec": (
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self.get_exec_input_gates(),
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self.get_exec_output_gates(),
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),
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}
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)
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