DpCompression Subtopology — Software Design Document (SDD)

The DpCompression subtopology packages the F´ data product compression services — a compression processor, a ZLib compressor, and a dedicated buffer manager — into a single pre-wired subtopology. It plugs into a data product pipeline (typically the DataProducts subtopology's dpWriterProcOut processing hook) to compress data products before they are stored and downlinked.

1. Requirements

ID	Description	Validation
SVC-DPCOMPRESSION-001	The subtopology shall provide data product compression processing for product buffers.	Inspection
SVC-DPCOMPRESSION-002	The subtopology shall provide ZLib-based compression of product data.	Inspection
SVC-DPCOMPRESSION-003	The subtopology shall provide buffer management for compression working and output buffers.	Inspection
SVC-DPCOMPRESSION-004	The subtopology shall support configurable buffer store properties (sizes, counts, allocator ID).	Inspection
SVC-DPCOMPRESSION-005	The subtopology shall expose a rate-group connection point for buffer manager telemetry.	Inspection

2. Design & Core Functions

2.1 Instance Summary

Instance name	Type (Svc)	Kind	Purpose (core function)
dpCompressProc	DpCompressProc	Passive	Receives product processing requests; chunks data for compression.
dpZLibCompressor	DpZLibCompressor	Passive	Compresses chunks using ZLib.
dpZLibCompressorBufferManager	BufferManager	Passive	Allocates compression working and output buffers.

2.2 Internal Wiring

• dpCompressProc.compressChunk -> dpZLibCompressor.compressChunk — chunks flow to the compressor.
• dpZLibCompressor.bufferCompressionGet / bufferCompressionReturn -> dpZLibCompressorBufferManager — compression output buffer allocation and return.
• dpZLibCompressor.bufferZLibGet / bufferZLibReturn -> dpZLibCompressorBufferManager — ZLib working buffer allocation and return.

2.3 Configuration Hooks inside the Subtopology

• dpZLibCompressorBufferManager: Two buffer bins are set up at startup from DpCompressionConfig::ZLibBuffMgr — one for compression output buffers and one for ZLib allocation (working) buffers — and cleaned up at teardown.

2.4 Required Inputs for Operation

The DpCompression subtopology is not a stand-alone application. It requires connections from the including deployment topology:

• Processing requests: Connect a data product processing output (e.g., DataProducts.Subtopology.dpWriterProcOut) to dpCompressProcIn.
• Rate group: Connect a scheduler output to dpZLibBufferManagerSchedIn for buffer manager telemetry.

3. Usage

3.1 Exposed Topology Ports

Port	Direction	Underlying port	Purpose
dpCompressProcIn	input	dpCompressProc.procRequest	Data product compression processing requests
dpZLibBufferManagerSchedIn	input	dpZLibCompressorBufferManager.schedIn	Rate-group scheduling for buffer manager telemetry

3.2 Example Usage

topology Flight {
  instance DataProducts.Subtopology
  instance DpCompression.Subtopology

  connections Compression {
    DataProducts.Subtopology.dpWriterProcOut -> DpCompression.Subtopology.dpCompressProcIn
  }

  connections RateGroups {
    rg1Hz.RateGroupMemberOut[3] -> DpCompression.Subtopology.dpZLibBufferManagerSchedIn
  }
}

4. Configuration

Configure the buffer store properties in Svc/Subtopologies/DpCompression/DpCompressionConfig/DpCompressionConfig.fpp:

• Base ID — Base identifier for the subtopology; component IDs are offset from this base.
• ZLibBuffMgr — Compression buffer store size/count, ZLib allocation buffer store size/count, and the buffer manager ID.

The memory allocator used by the subtopology is provided by DpCompressionSubtopologyConfig.cpp (DpCompression::Allocation::memAllocator).

5. Traceability Matrix

Requirement ID	Satisfied by
SVC-DPCOMPRESSION-001	dpCompressProc — Svc.DpCompressProc
SVC-DPCOMPRESSION-002	dpZLibCompressor — Svc.DpZLibCompressor
SVC-DPCOMPRESSION-003	dpZLibCompressorBufferManager — Svc.BufferManager
SVC-DPCOMPRESSION-004	DpCompressionConfig::ZLibBuffMgr constants
SVC-DPCOMPRESSION-005	dpZLibBufferManagerSchedIn topology port