feat PageReassembler

[David-A-T-M]

Implement PageReassembler Service

Description

Implement the PageReassembler class. Unlike previous data models, this is a mutable stateful class responsible for collecting incoming Packet objects and reconstructing a full Page once all fragments are received.

Technical Specifications

• Type: Standard Java class (not a record, as it requires mutable state).
• Internal Storage: Use a fixed-size array Packet[] to store fragments at their respective pagePos. This allows $O(1)$ access and clear visibility of missing slots (null).
• Fields:
  • long pageId: The ID of the page being reassembled.
  • IpAddress srcIp: Expected source address for validation.
  • int total: Total number of packets expected.
  • int count: Current number of packets received.
  • long timeout: Absolute simulation tick when this assembler should be discarded if incomplete.
• Key Methods:
  • boolean addPacket(Packet p): Validates metadata (ID, IP, length) and places the packet in the array. Returns true if added, false if redundant or invalid.
  • boolean isComplete(): Returns true if count == total.
  • Page package(): Produces a final Page object if complete. Throws an exception if called prematurely.
  • double getCompletionRate(): Returns the percentage of received packets.

Validation logic

• The constructor must initialize the Packet[] array with the size of total.
• addPacket must ignore packets that don't match the pageId or srcIp of the reassembler.
• Prevent duplicate packet insertion (check if packets[pos] != null).

Tasks

• Create PageReassembler.java in the assembler (or service) package.
• Implement state management logic.
• Add unit tests in PageReassemblerTest.java:
  • Successful full reassembly.
  • Handling of out-of-order packets.
  • Prevention of inconsistent packet insertion.
  • Validation of completion logic.
• Verify 100% branch coverage with JaCoCo.