Skip to content

Latest commit

 

History

History
81 lines (46 loc) · 4.14 KB

USAGE.md

File metadata and controls

81 lines (46 loc) · 4.14 KB

Usage Guide for static-dag

Introduction

The static-dag library is designed to facilitate the creation and management of Directed Acyclic Graphs (DAGs) in embedded environments. In this system, the smallest unit of management is the DAGNode. Users can embed DAGNode into any struct, making that struct a manageable node within the DAG.

This guide will walk you through the process of defining, creating, and managing nodes using the static-dag librar.

Declaring a Struct with DAGNode

The library provides a DAGNode macro to assist users in embedding a DAGNode into any struct. This allows the struct to become a node within the DAG. The macro usage is as follows:

Place DAGNode(name, in_degree); within the structure definition to create a DAGNode member named name with a maximum in-degree of in_degree.

Example

struct Foo {
    char *bar;
    DAGNode(node, 3);
};

In this example, we declare a struct Foo that contains a DAGNode named node with an in-degree of 3. This means that the node can have up to 3 incoming edges in the DAG.

Initializing a Node

The library provides a macro DAGNodeInit to initialize a node. It is crucial to initialize a node before using it in your DAG operations. The macro sets up the internal state of the node, allowing it to function correctly within the DAG.

Usage

DAGNodeInit(node, node_op)

  • node: The node to initialize (this corresponds to the node member in your custom structure).
  • node_op: A function table that defines the operations for this node. The functions that can be registered in node_op will be introduced in the following sections.

Adding relationships

To define the relationships between nodes in the DAG, you can use the add_ancestor function. This function adds an ancestor to the specified node, allowing you to build the directed connections within the graph.

Usage

add_ancestor(node, ancestor)

  • node: Pointer to the target node to which you want to add an ancestor.
  • ancestor: Pointer to the node that you want to set as an ancestor of the target node.

Removing a Node

To remove a node from the DAG, use the remove_node function. This function detaches the specified node from the graph, provided that it has no ancestors. If the node still has ancestors, it cannot be removed.

When a node is removed, its dependent relationships with its descendants are also removed, effectively isolating those nodes from the removed node.

Usage

remove_node(my_node)

  • node: Pointer to the node you want to remove from the DAG.

DAGop Structure

The DAGop structure defines a set of operations (callbacks) that can be associated with a DAGNode. These operations allow you to customize how nodes behave in various situations, such as when they are freed, printed, or when all their ancestors have been removed. The DAGop structure is passed to DAGNodeInit during the initialization of a node.

Available Operations

  1. free: A callback function that is called when a node is freed. It can be used to clean up resources associated with the node.

    • Signature: void (*free)(struct DAGNode *self);
    • Example Usage: This function can be customized to release memory or reset the state of the node.

  2. print: A callback function to print the node's details. This is useful for debugging or visualizing the state of the DAG.

    • Signature: void (*print)(struct DAGNode *self);
    • Example Usage: Define this function to output information about the node's current state, such as its ID or its relationships.

  3. on_all_ancestors_freed: A callback function that is called when all ancestors of the node have been removed. This function allows you to define custom behavior for when a node becomes independent.

    • Signature: void (*on_all_ancestors_freed)(struct DAGNode *self);
    • Example Usage: This can be used to perform specific actions when the node no longer has any dependencies in the graph.

When defining a DAGNode, you will typically provide a DAGop structure with your custom implementations for these operations, allowing you to tailor the node's behavior to the needs of your application.