Queue

Introduction

This document describes the queue component of EasyEmbeddedFramework. It explains the structure, behavior, and data types used in the queue implementation. The queue component provides a flexible, memory-efficient FIFO data structure for embedded systems.

The queue component allows users to:

• Create queues with static memory allocation

• Push and pop elements from both front and back

• Reserve elements for later insertion

• Access front and back elements

• Query queue status and size

Limitations:

• The queue is not thread-safe by default

• Memory must be provided by the user

• Not suitable for real-time or high-frequency operations without additional synchronization

Use cases:

• Buffering sensor data

• Task scheduling

• Event/message passing between components

Component’s structure

The queue component is composed of the following sub-components:

• ezQueue: Main queue structure containing a linked list of items and a memory list for static allocation

• ezQueueItem: Represents each element in the queue, holding data and metadata

• Node: Linked list node for queue item management

• MemList: Manages memory allocation for queue items and their data

Mermaid diagram:

        classDiagram
   class ezQueue {
      Node q_item_list
      MemList mem_list
   }
   class ezQueueItem {
      void* data
      uint32_t data_size
      Node node
   }
   class Node {
      +pointer next
   }
   class MemList {
      +allocate()
      +deallocate()
   }
   ezQueue --> ezQueueItem
   ezQueue --> Node
   ezQueue --> MemList
   ezQueueItem --> Node
    

Component’s behavior

External behavior:

• Users can create a queue, push data, pop elements, reserve memory for elements, and access queue status.

• The queue operates in FIFO mode but supports popping from both front and back.

• Memory management is handled internally via static allocation, but the buffer must be provided by the user.

Internal behavior:

• The queue uses a linked list to manage elements.

• Memory for each element and its data is allocated from a static memory pool.

• Reserved elements are not linked to the queue until explicitly pushed.

• Elements can be released if not needed, freeing their memory.

• The queue tracks the number of elements and readiness status.

Component’s data type

The queue component uses the following data types:

• ezQueue: Structure representing the queue

• ezQueueItem: Structure representing each queue element

• ezReservedElement: Pointer to reserved element memory

• Node: Linked list node

• MemList: Static memory allocation manager

• ezSTATUS: Status code (ezSUCCESS, ezFAIL)

• uint8_t, uint32_t: Standard integer types for data and sizes

Data passed to the queue is managed as void pointers, allowing flexibility for different data types.