Module disk_writer

ISO Streaming Disk Writer State Machine.

Writes ISO data to disk in chunks as it arrives from the network. Operates in tandem with HTTP download state machine.

Design

• Non-blocking: Uses fire-and-forget block I/O
• Streaming: Writes arrive in chunks, queued to disk
• Backpressure: Pauses HTTP when write queue is full
• Progress: Tracks bytes written and completion status

Architecture

HTTP Download ──┬── Data Chunk ──▶ DiskWriter ──▶ VirtIO-blk
                │
                └── Backpressure ◀────────────────┘

Reference

NETWORK_IMPL_GUIDE.md §5, §8

Structs

• ChunkQueue
  Chunk queue for buffering writes.
• DiskWriterConfig
  Disk writer configuration.
• DiskWriterProgress
  Disk write progress.
• DiskWriterState
  ISO streaming disk writer state machine.
• PendingWrite 🔒
  Pending write request.
• WriteChunk
  Write chunk descriptor for queuing.

Enums

• DiskWriterError
  Disk writer errors.
• WriterState
  Disk writer state.

Constants

• CHUNK_SIZE
  Chunk size in bytes (64KB).
• MAX_PENDING_WRITES 🔒
  Maximum number of in-flight write requests.
• SECTORS_PER_CHUNK
  Sectors per write chunk (128 sectors = 64KB at 512B/sector).